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DESCRIPTION
The WM8987L is a low power, high quality stereo CODEC designed for portable digital audio applications. The device integrates complete interfaces to stereo or mono microphones and a stereo BTL (differential) or single-ended headset. External component requirements are reduced as no separate microphone or headphone amplifiers are required. Advanced on-chip digital signal processing performs equalisation, 3-D sound enhancement and automatic level control for the microphone or line input. The WM8987L can operate as a master or a slave, with various master clock frequencies including 12 or 24MHz for USB devices, or standard 256fs rates like 12.288MHz and 24.576MHz. Different audio sample rates such as 96kHz, 48kHz, 44.1kHz are generated directly from the master clock without the need for an external PLL. The WM8987L operates at supply voltages down to 1.8V, although the digital core can operate at voltages down to 1.42V to save power, and the maximum for all supplies is 3.6 Volts. Different sections of the chip can also be powered down under software control. The WM8987L is supplied in a very small and thin 4x4mm COL package, ideal for use in ultra-portable and wearable systems.
WM8987L
Stereo CODEC for Portable Audio Applications
FEATURES
* * DAC SNR 98dB, ADC 90dB (`A' weighted) at 48kHz, 3.3V On-chip Headphone Driver - Single-ended or BTL (differential) drive - >40mW output power on 16 / 3.3V - DAC to 32 BTL headphone: SNR 86dB, THD -66dB Complete Stereo / Mono Microphone Interface - Differential or single-ended mic connection - Programmable ALC / Noise Gate Digital Equaliser Low Power - Stereo playback 8 mW (1.8V / 1.5V supplies) - Record and playback 13 mW (1.8V / 1.5V supplies) Low Supply Voltages - Analogue 1.8V to 3.6V - Digital core: 1.42V to 3.6V - Digital I/O: 1.8V to 3.6V 256fs / 384fs or USB master clock rates: 12MHz, 24MHz Audio sample rates: 8, 11.025, 16, 22.05, 24, 32, 44.1, 48, 88.2, 96kHz generated internally from master clock 4x4mm COL package Register compatible with WM8750L
* * * *
* * * *
APPLICATIONS
* * Wireless Headsets Portable Music Player / Recorders
BLOCK DIAGRAM
WOLFSON MICROELECTRONICS plc
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Pre-Production, January 2007, Rev 3.0
Copyright 2007 Wolfson Microelectronics plc
WM8987L TABLE OF CONTENTS
Pre-Production
DESCRIPTION .......................................................................................................1 FEATURES.............................................................................................................1 APPLICATIONS .....................................................................................................1 BLOCK DIAGRAM .................................................................................................1 TABLE OF CONTENTS .........................................................................................2 PIN CONFIGURATION...........................................................................................3 ORDERING INFORMATION ..................................................................................3 PIN DESCRIPTION ................................................................................................4 ABSOLUTE MAXIMUM RATINGS.........................................................................5 RECOMMENDED OPERATION CONDITIONS .....................................................5 ELECTRICAL CHARACTERISTICS ......................................................................6 TYPICAL PERFORMANCE....................................................................................8
POWER CONSUMPTION.............................................................................................. 8 HEADPHONE OUTPUT THD VERSUS POWER (TYPICAL)......................................... 9 OUTPUT PGA'S LINEARITY ....................................................................................... 10
SIGNAL TIMING REQUIREMENTS .....................................................................11
SYSTEM CLOCK TIMING............................................................................................ 11 AUDIO INTERFACE TIMING - MASTER MODE ......................................................... 11 AUDIO INTERFACE TIMING - SLAVE MODE ............................................................ 12
INTERNAL POWER ON RESET CIRCUIT ..........................................................15 DEVICE DESCRIPTION.......................................................................................16
INTRODUCTION.......................................................................................................... 16 INPUT SIGNAL PATH.................................................................................................. 16 AUTOMATIC LEVEL CONTROL (ALC) ....................................................................... 23 OUTPUT SIGNAL PATH.............................................................................................. 27 ANALOGUE OUTPUTS ............................................................................................... 32 DIGITAL AUDIO INTERFACE...................................................................................... 35 AUDIO INTERFACE CONTROL .................................................................................. 38 CLOCKING AND SAMPLE RATES .............................................................................. 40 CONTROL INTERFACE .............................................................................................. 42 POWER SUPPLIES ..................................................................................................... 43 POWER MANAGEMENT ............................................................................................. 44
REGISTER MAP...................................................................................................46 DIGITAL FILTER CHARACTERISTICS ...............................................................47
TERMINOLOGY........................................................................................................... 47 DAC FILTER RESPONSES ......................................................................................... 48 ADC FILTER RESPONSES ......................................................................................... 49 DE-EMPHASIS FILTER RESPONSES ........................................................................ 50 HIGHPASS FILTER ..................................................................................................... 51
APPLICATIONS INFORMATION .........................................................................52
RECOMMENDED EXTERNAL COMPONENTS........................................................... 52 DRIVING BTL HEADSETS........................................................................................... 53 DRIVING SINGLE-ENDED HEADPHONES ................................................................. 53 MICROPHONE INPUT CONFIGURATION .................................................................. 55 LINE INPUT CONFIGURATION................................................................................... 56 MINIMISING POP NOISE AT THE ANALOGUE OUTPUTS ........................................ 56 POWER MANAGEMENT EXAMPLES ......................................................................... 56
IMPORTANT NOTICE ..........................................................................................58
ADDRESS.................................................................................................................... 58
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PIN CONFIGURATION
ORDERING INFORMATION
ORDER CODE WM8987LGECO/V WM8987LGECO/RV Note: Reel quantity = 3,500 TEMPERATURE RANGE -25C to +85C -25C to +85C PACKAGE 28-lead COL QFN (4x4mm) (Pb-free) 28-lead COL QFN (4x4mm) (Pb-free, tape and reel) MOISTURE PEAK SOLDERING SENSITIVITY LEVEL TEMPERATURE MSL3 MSL3 260C 260C
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WM8987L PIN DESCRIPTION
PIN NO 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 NAME MCLK DCVDD DBVDD DGND BCLK DACDAT DACLRC ADCLRC ADCDAT OUT3 ROUT1 HPGND ROUT2 LOUT2 HPVDD AVDD AGND VREF VMID MICBIAS RINPUT2 LINPUT2 RINPUT1 LINPUT1 MODE CSB SDIN SCLK Supply Supply Supply Digital Input / Output Digital Input Digital Input / Output Digital Input / Output Digital Output Analogue Output Analogue Output Supply Analogue Output Analogue Output Supply Supply Supply Analogue Output Analogue Output Analogue Output Analogue Input Analogue Input Analogue Input Analogue Input Digital Input Digital Input Digital Input/Output Digital Input TYPE Digital Input Master Clock Digital Core Supply Digital Buffer (I/O) Supply DESCRIPTION
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Digital Ground (return path for both DCVDD and DBVDD) Audio Interface Bit Clock DAC Digital Audio Data Audio Interface Left / Right Clock/Clock Out Audio Interface Left / Right Clock ADC Digital Audio Data Analogue Output 3 (HPL- for BTL headsets) Right Output 1 (HPR+ for BTL headsets) Supply for Analogue Output Drivers (ROUT1, L/ROUT2, OUT3) Right Output 2 (HPR- for BTL headsets) Left Output 2 (HPL+ for BTL headsets) Supply for Analogue Output Drivers (ROUT1, L/ROUT2, OUT3) Analogue Supply Analogue Ground (return path for AVDD) Reference Voltage Decoupling Capacitor Midrail Voltage Decoupling Capacitor Microphone Bias Right Channel Input 2 Left Channel Input 2 Right Channel Input 1 Left Channel Input 1 Control Interface Selection Chip Select / Device Address Selection Control Interface Data Input / 2-wire Acknowledge output Control Interface Clock Input
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ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings are stress ratings only. Permanent damage to the device may be caused by continuously operating at or beyond these limits. Device functional operating limits and guaranteed performance specifications are given under Electrical Characteristics at the test conditions specified.
ESD Sensitive Device. This device is manufactured on a CMOS process. It is therefore generically susceptible to damage from excessive static voltages. Proper ESD precautions must be taken during handling and storage of this device. Wolfson tests its package types according to IPC/JEDEC J-STD-020B for Moisture Sensitivity to determine acceptable storage conditions prior to surface mount assembly. These levels are: MSL1 = unlimited floor life at <30C / 85% Relative Humidity. Not normally stored in moisture barrier bag. MSL2 = out of bag storage for 1 year at <30C / 60% Relative Humidity. Supplied in moisture barrier bag. MSL3 = out of bag storage for 168 hours at <30C / 60% Relative Humidity. Supplied in moisture barrier bag. The Moisture Sensitivity Level for each package type is specified in Ordering Information. CONDITION Supply voltages Voltage range digital inputs Voltage range analogue inputs Operating temperature range, TA Storage temperature after soldering Notes 1. 2. Analogue and digital grounds must always be within 0.3V of each other. DCVDD must be less than or equal to AVDD and DBVDD. MIN -0.3V DGND -0.3V AGND -0.3V -25C -65C MAX +3.63V DBVDD +0.3V AVDD +0.3V +85C +150C
RECOMMENDED OPERATION CONDITIONS
PARAMETER Digital supply range (Core) Digital supply range (Buffer) Analogue supplies range Ground SYMBOL DCVDD DBVDD AVDD, HPVDD DGND,AGND, HPGND MIN 1.42 1.7 1.8 0 TYP MAX 3.6 3.6 3.6 UNIT V V V V
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WM8987L ELECTRICAL CHARACTERISTICS
Test Conditions DCVDD = 1.5V, DBVDD = 3.3V, AVDD = HPVDD = 3.3V, TA = +25oC, 1kHz signal, fs = 48kHz, PGA gain = 0dB, ADCOSR = DACOSR = 1 (64 fs), 24-bit audio data unless otherwise stated. PARAMETER Full Scale Input Signal Level (for ADC 0dB Input at 0dB Gain) Input Resistance SYMBOL VINFS TEST CONDITIONS AVDD = 3.3V AVDD = 1.8V L/RINPUT1 to ADC, PGA gain = 0dB L/RINPUT1 to ADC, PGA gain = +30dB L/RINPUT1 unused DC Measurement L/RINPUT1 unused Input Capacitance Signal to Noise Ratio (A-weighted) Total Harmonic Distortion SNR THD AVDD = 3.3V AVDD = 1.8V -1dBFs input, AVDD = 3.3V -1dBFs input, AVDD = 1.8V ADC Channel Separation Channel Matching Full scale output voltage across BTL load Output Power per channel Total Harmonic Distortion 0dBFS PO THD 1kHz signal 1kHz signal LOUT2-OUT3, ROUT1-ROUT2 AVDD=HPVDD=1.8V, RL=32, PO=5mW AVDD=HPVDD =1.8V, RL=16, PO=5mW Signal to Noise Ratio (A-weighted) Full scale output voltage Output Power per channel Total Harmonic Distortion SNR AVDD=HPVDD =1.8V, RL=32 LOUT2, ROUT2 HPVDD=3.3V, RL=32, PO=5mW HPVDD=3.3V, RL=16, PO=5mW Signal to Noise Ratio (A-weighted) Full scale output voltage Output Power per channel Total Harmonic Distortion SNR AVDD=HPVDD =3.3V 92 80 80 MIN TYP 1.0 0.545 22 1.5 16 17 10 90 87 -80 0.01 -70 0.03 88 0.04 AVDD/1.65 MAX
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UNIT V rms k
Analogue Inputs (LINPUT1, RINPUT1, LINPUT2, RINPUT2) to ADC out
pF dB dB %
dB % Vrms
DAC to BTL headset drive (left=LOUT2/OUT3, right=ROUT1/ROUT2)
Output power is very closely correlated with THD; see below. -66 0.05 -62 0.08 86 dB -58 0.13 dB %
DAC to single-ended headset drive (LOUT2/ROUT2, using capacitors) 0dBFS PO THD AVDD/3.3 -61 0.09 -60 0.1 98 -52 0.25 -52 0.25 dB Vrms dB % Output power is very closely correlated with THD; see below.
DAC to single-ended headset drive (capless, using OUT3 as headphone ground) 0dBFS PO THD LOUT2-OUT3, ROUT2-OUT3 HPVDD=3.3V, RL=32, PO=5mW HPVDD=3.3V, RL=16, PO=5mW AVDD/3.3 Vrms
Output power is very closely correlated with THD; see below. -61 0.09 -60 0.1 dB %
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Pre-Production Test Conditions DCVDD = 1.5V, DBVDD = 3.3V, AVDD = HPVDD = 3.3V, TA = +25oC, 1kHz signal, fs = 48kHz, PGA gain = 0dB, ADCOSR = DACOSR = 1 (64 fs), 24-bit audio data unless otherwise stated. PARAMETER Signal to Noise Ratio (A-weighted) Analogue Reference Levels Midrail Reference Voltage Buffered Reference Voltage Microphone Bias Bias Voltage Bias Current Source Output Noise Voltage Digital Input / Output Input HIGH Level Input LOW Level Output HIGH Level Output LOW Level VIH VIL VOH VOL IOH = +1mA IOL = -1mA 0.9xDBVDD 0.7xDBVDD VMICBIAS IMICBIAS Vn 1K to 20kHz 15 3mA load current -5% 0.9xAVDD + 5% 3 VMID VREF -3% -3% AVDD/2 AVDD/2 +3% +3% SYMBOL SNR TEST CONDITIONS AVDD=HPVDD =3.3V MIN TYP 98 MAX
WM8987L
UNIT dB
V V V mA nV/Hz V
0.3xDBVDD 0.1xDBVDD
V V V
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WM8987L TYPICAL PERFORMANCE
POWER CONSUMPTION
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The power consumption of the WM8987L depends on the following factors. * Supply voltages: Reducing the supply voltages also reduces supply currents, and therefore results in significant power savings, especially in the digital sections of the WM8987L. * Operating mode: Significant power savings can be achieved by always disabling parts of the WM8987L that are not used (e.g. mic pre-amps, unused outputs, DAC, ADC, etc.)
Control Register Code POF-01 POF-02 POF-03 PST-01 PST-02 PST-03 PPB-01 PPB-02 PPB-03 PPS-01 PPS-02 PPS-03 PPC-01 PPC-02 PPC-03 PRD-01 PRD-02 PRD-03 PRS-01 PRS-02 PRS-03 PRL-01 PRL-02 PRL-03 PDL-01 PDL-02 PDL-03 Bit OFF VMIDSEL R25 (19h) R26 (1Ah) R24 (18h) R23 VSEL Other settings AVDD DCVDD DBVDD HPVDD Tot. Power
VREF AINL AINR ADCL ADCR MICB DIGENB DACL DACR ROUT1 LOUT2 ROUT2 MONO OUT3 OUT3SW ROUT2INV ADCOSR DACOSR
Standby (500 KOhm VMID string) BTL Headset Stereo Playback 0.1mW/channel into 32 Ohm load Single-ended Headset Stereo Playback 0.1mW/channel into 32 Ohm load Single-ended Headset Stereo Playback (capless mode using OUT3) 0.1mW/channel into 32 Ohm load Differential mono mic record (LINPUT1-RINPUT1) Single-ended mono mic record (from LINPUT1) Single-ended stereo line record (from L/RINPUT1) Simultaneous record and playback (stereo, line-in / line-out)
00 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 11 01 00 10 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 11 01 00 01 1 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 11 01 00 01 1 0 0 0 0 0 0 1 1 0 1 1 0 0 0 0 1 1 11 01 00 01 1 0 0 0 0 0 0 1 1 0 1 1 0 1 0 0 1 1 11 01 00 01 1 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 1 1 11 01 00 01 1 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 1 1 11 01 00 01 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 1 1 11 01 00 01 1 1 1 1 1 0 0 1 1 0 1 1 0 0 0 0 1 1 11 01 00
Clocks stopped
Interface Stopped
LINSEL=11 LMICBOOST=10 DATSEL=01 LMICBOOST=10 DATSEL=01
V 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8
I (mA) 0.000 0.000 0.000 0.482 0.310 0.184 2.573 2.052 1.297 2.232 1.778 1.126 2.229 1.776 1.126 3.551 3.077 2.388 3.196 2.799 2.221 4.532 4.037 3.313 6.295 5.454 4.212
V 3.3 2.0 1.5 3.3 2.0 1.5 3.3 2.0 1.5 3.3 2.0 1.5 3.3 2.0 1.5 3.3 2.0 1.5 3.3 2.0 1.5 3.3 2.0 1.5 3.3 2.0 1.5
I (mA) 0.010 0.007 0.007 0.011 0.008 0.007 4.601 2.371 1.750 4.662 2.411 1.758 4.662 2.408 1.757 4.883 2.255 1.584 4.888 2.270 1.588 4.917 2.281 1.605 7.836 3.837 2.760
V 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8
I (mA) 0.000 0.000 0.000 0.000 0.000 0.000 0.248 0.175 0.119 0.248 0.175 0.119 0.248 0.175 0.119 0.298 0.213 0.148 0.295 0.212 0.146 0.287 0.206 0.142 0.286 0.206 0.142
V 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8 3.3 2.7 1.8
I (mA) 0.000 0.000 0.000 0.000 0.000 0.000 4.291 4.314 3.879 2.005 2.021 1.856 4.007 4.007 3.674 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.679 0.711 0.364
mW 0.033 0.014 0.011 1.627 0.853 0.342 38.653 22.368 12.156 30.185 15.517 8.219 36.782 20.868 11.490 28.816 13.350 6.941 27.651 12.627 6.643 32.129 15.977 8.627 49.817 24.835 12.632
Table 1 Typical Supply Current Consumption
Notes: 1. 2. All figures are at TA = +25oC, Slave Mode, fs = 48kHz, MCLK = 12.288 MHz (256fs), with zero signal (quiescent) The power dissipated in the headphone or speaker is not included in the above table.
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HEADPHONE OUTPUT THD VERSUS POWER (TYPICAL)
WM8987 THD+N v Output Power BTL Headset Drive
100 16ohm 3.3V 16ohm 2.7V 1 16ohm 1.8V 32ohm 3.3V 32ohm 2.7V 0.1 32ohm 1.8V
10 THD+N (%)
0.01 0.1 1 10 100
Output Power (mW)
WM8987 THD+N v Output Power Single Ended Headset Drive (AC Coupled)
10 16ohm 3.3V THD+N (%) 1 16ohm 2.7V 16ohm 1.8V 32ohm 3.3V 0.1 32ohm 2.7V 32ohm 1.8V
0.01 0.1 1 10 100
Output Power (mW)
WM8987 THD+N v Output Power Single Ended Headset Drive (Capless)
10
16ohm 3.3V
1 THD+N (%)
16ohm 2.7V 16ohm 1.8V 32ohm 3.3V 32ohm 2.7V 32ohm 1.8V
0.1
0.01 0.1 1 10 100
Output Power (mW)
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OUTPUT PGA'S LINEARITY
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10.000 0.000 Output PGA Gains -10.000 Measured Gain [dB] -20.000 -30.000 -40.000 -50.000 -60.000 -70.000 40 50 60 70 80 90 100 110 120 130 XXXVOL Register Setting (binary) ROUT1 LOUT2 ROUT2 MONOOUT
2.00 1.75 Output PGA Gain Step Size 1.50 Step Size [dB] 1.25 1.00 0.75 ROUT1 0.50 0.25 0.00 40 50 60 70 80 90 100 110 120 130 LOUT2 ROUT2 MONOOUT
XXXVOL Register Setting (binary)
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SIGNAL TIMING REQUIREMENTS
SYSTEM CLOCK TIMING
tMCLKL MCLK tMCLKH tMCLKY
Figure 1 System Clock Timing Requirements Test Conditions CLKDIV2=0, DCVDD = 1.42V, DBVDD = 3.3V, DGND = 0V, TA = +25oC, Slave Mode fs = 48kHz, MCLK = 384fs, 24-bit data, unless otherwise stated. PARAMETER System Clock Timing Information MCLK System clock pulse width high MCLK System clock pulse width low MCLK System clock cycle time MCLK duty cycle TMCLKL TMCLKH TMCLKY TMCLKDS 21 21 54 60:40 40:60 ns ns ns SYMBOL MIN TYP MAX UNIT
Test Conditions CLKDIV2=1, DCVDD = 1.42V, DBVDD = 3.3V, DGND = 0V, TA = +25oC, Slave Mode fs = 48kHz, MCLK = 384fs, 24-bit data, unless otherwise stated. PARAMETER System Clock Timing Information MCLK System clock pulse width high MCLK System clock pulse width low MCLK System clock cycle time TMCLKL TMCLKH TMCLKY 10 10 27 ns ns ns SYMBOL MIN TYP MAX UNIT
AUDIO INTERFACE TIMING - MASTER MODE
BCLK (Output) ADCLRC/ DACLRC (Outputs) tDL
tDDA ADCDAT
DACDAT tDST tDHT
Figure 2 Digital Audio Data Timing - Master Mode (see Control Interface)
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Test Conditions
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DCVDD = 1.42V, DBVDD = 3.3V, DGND = 0V, TA = +25oC, Slave Mode, fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER SYMBOL MIN TYP MAX UNIT Bit Clock Timing Information BCLK rise time (10pF load) BCLK fall time (10pF load) BCLK duty cycle (normal mode, BCLK = MCLK/n) BCLK duty cycle (USB mode, BCLK = MCLK) Audio Data Input Timing Information ADCLRC/DACLRC propagation delay from BCLK falling edge ADCDAT propagation delay from BCLK falling edge DACDAT setup time to BCLK rising edge DACDAT hold time from BCLK rising edge tDL tDDA tDST tDHT 10 10 10 40 ns ns ns ns tBCLKR tBCLKF tBCLKDS tBCLKDS 50:50 TMCLKDS 3 3 ns ns
AUDIO INTERFACE TIMING - SLAVE MODE
tBCH BCLK tBCY DACLRC/ ADCLRC tDS DACDAT tDD ADCDAT tDH tLRH tLRSU tBCL
Figure 3 Digital Audio Data Timing - Slave Mode
Test Conditions DCVDD = 1.42V, DBVDD = 3.3V, DGND = 0V, TA = +25oC, Slave Mode, fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER SYMBOL MIN TYP MAX UNIT Audio Data Input Timing Information BCLK cycle time BCLK pulse width high BCLK pulse width low ADCLRC/DACLRC set-up time to BCLK rising edge ADCLRC/DACLRC hold time from BCLK rising edge DACDAT hold time from BCLK rising edge ADCDAT propagation delay from BCLK falling edge Note: BCLK period should always be greater than or equal to MCLK period. tBCY tBCH tBCL tLRSU tLRH tDH tDD 50 20 20 10 10 10 10 ns ns ns ns ns ns ns
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CONTROL INTERFACE TIMING - 3-WIRE MODE
tCSL CSB tCSS tSCL tSCS tCSH
tSCY tSCH SCLK
SDIN tDSU tDHO
LSB
Figure 4 Control Interface Timing - 3-Wire Serial Control Mode Test Conditions DCVDD = 1.42V, DBVDD = 3.3V, DGND = 0V, TA = +25oC, Slave Mode, fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER SYMBOL MIN TYP MAX UNIT Program Register Input Information SCLK rising edge to CSB rising edge SCLK pulse cycle time SCLK pulse width low SCLK pulse width high SDIN to SCLK set-up time SCLK to SDIN hold time CSB pulse width low CSB pulse width high CSB rising to SCLK rising Pulse width of spikes that will be suppressed tSCS tSCY tSCL tSCH tDSU tDHO tCSL tCSH tCSS tps 80 200 80 80 40 40 40 40 40 0 5 ns ns ns ns ns ns ns ns ns ns
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WM8987L
CONTROL INTERFACE TIMING - 2-WIRE MODE
t3 SDIN t4 t6 SCLK t1 t9 t7 t2 t5 t3
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t8
Figure 5 Control Interface Timing - 2-Wire Serial Control Mode Test Conditions DCVDD = 1.42V, DBVDD = 3.3V, DGND = 0V, TA = +25oC, Slave Mode, fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER SYMBOL MIN TYP MAX UNIT Program Register Input Information SCLK Frequency SCLK Low Pulse-Width SCLK High Pulse-Width Hold Time (Start Condition) Setup Time (Start Condition) Data Setup Time SDIN, SCLK Rise Time SDIN, SCLK Fall Time Setup Time (Stop Condition) Data Hold Time Pulse width of spikes that will be suppressed t1 t2 t3 t4 t5 t6 t7 t8 t9 tps 0 600 900 5 0 1.3 600 600 600 100 300 300 526 kHz us ns ns ns ns ns ns ns ns ns
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INTERNAL POWER ON RESET CIRCUIT
DCVDD AVDD T1 VDD Power on Reset Circuit GND DGND
Figure 6 Internal Power on Reset Circuit Schematic The WM8987L includes an internal Power-On-Reset Circuit, as shown below, which is used to reset the digital logic into a default state after power up. The power on reset circuit is powered from DCVDD and monitors DCVDD and AVDD. It asserts PORB low if DCVDD or AVDD are below a minimum threshold.
Internal PORB
Figure 7 Typical Power-Up Sequence Figure 7 shows a typical power-up sequence. When DCVDD and AVDD rise above the minimum thresholds, Vpord_dcvdd and Vpord_avdd, there is enough voltage for the circuit to guarantee the Power on Reset is asserted low and the chip is held in reset. In this condition, all writes to the control interface are ignored. When DCVDD rises to Vpor_dcvdd_on and AVDD rises to Vpor_avdd_on, PORB is released high and all registers are in their default state and writes to the control interface may take place. If DCVDD and AVDD rise at different rates then PORB will only be released when DCVDD and AVDD have both exceeded the Vpor_dcvdd_on and Vpor_avdd_on thresholds. On power down, PORB is asserted low whenever DCVDD drops below the minimum threshold Vpor_dcvdd_off or AVDD drops below the minimum threshold Vpor_avdd_off.
SYMBOL Vpord_dcvdd Vpor_dcvdd_on Vpor_avdd_on Vpor_avdd_off
MIN 0.4 0.9 0.5 0.4
TYP 0.6 1.26 0.7 0.6
MAX 0.8 1.6 0.9 0.8
UNIT V V V V
Table 2 Typical POR Operation (typical values, not tested)
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WM8987L DEVICE DESCRIPTION
INTRODUCTION
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The WM8987L is a low power audio codec offering a combination of high quality audio, advanced features, low power and small size. These characteristics make it ideal for portable digital audio applications such as MP3 and minidisk player / recorders. Stereo 24-bit multi-bit delta sigma ADCs and DACs are used with oversampling digital interpolation and decimation filters. The device includes three stereo analogue inputs that can be switched internally. Each can be used as either a line level input or microphone input and LINPUT1/RINPUT1 and LINPUT2/RINPUT2 can be configured as mono differential inputs. A programmable gain amplifier with automatic level control (ALC) keeps the recording volume constant. The on-chip stereo ADC and DAC are of a high quality using a multi-bit, low-order oversampling architecture to deliver optimum performance with low power consumption. The DAC output signal first enters an analogue mixer where an analogue input and/or the post-ALC signal can be added to it. This mix is available on line and headphone outputs. The WM8987L has a configurable digital audio interface where ADC data can be read and digital audio playback data fed to the DAC. It supports a number of audio data formats including I2S, DSP Mode (a burst mode in which frame sync plus 2 data packed words are transmitted), and MSB-First, left justified. It can operate in master or slave modes. The WM8987L uses a unique clocking scheme that can generate many commonly used audio sample rates from either a 12.00MHz USB clock or an industry standard 256/384 fs clock. This feature eliminates the common requirement for an external phase-locked loop (PLL) in applications where the master clock is not an integer multiple of the sample rate. Sample rates of 8kHz, 11.025kHz, 12kHz, 16kHz, 22.05kHz, 24kHz, 32kHz, 44.1kHz, 48kHz, 88.2kHz and 96kHz can be generated. The digital filters used for recording and playback are optimised for each sampling rate used. To allow full software control over all its features, the WM8987L offers a choice of 2 or 3 wire MPU control interface. It is fully compatible and an ideal partner for a wide range of industry standard microprocessors, controllers and DSPs. The design of the WM8987L has given much attention to power consumption without compromising performance. It operates at very low voltages, and includes the ability to power off parts of the circuitry under software control, including standby and power off modes.
INPUT SIGNAL PATH
The input signal path for each channel consists of a switch to select between three analogue inputs, followed by a PGA (programmable gain amplifier) and an optional microphone gain boost. A differential input of either (LINPUT1 - RINPUT1) or (LINPUT2 - RINPUT2) may also be selected. The gain of the PGA can be controlled either by the user or by the on-chip ALC function (see Automatic Level Control). The signal then enters an ADC where it is digitised. Alternatively, the two channels can also be mixed in the analogue domain and digitised in one ADC while the other ADC is switched off. The mono-mix signal appears on both digital output channels.
SIGNAL INPUTS
The WM8987L has two sets of high impedance, low capacitance AC coupled analogue inputs, LINPUT1/RINPUT1 and LINPUT2/RINPUT2. Inputs can be configured as microphone or line level by enabling or disabling the microphone gain boost. LINSEL and RINSEL control bits (see Table 4) are used to select independently between external inputs and internally generated difference signals (LINPUT1-RINPUT1 or LINPUT2-RINPUT2). The choice of difference signal, LINPUT1-RINPUT1 or LINPUT2-RINPUT2 is made using the DS bit (see below). REGISTER ADDRESS R31 (1Fh) ADC Input Mode BIT 8 DS LABEL DEFAULT 0 DESCRIPTION Differential input select 0: LINPUT1 - RINPUT1 1: LINPUT2 - RINPUT2
Table 3 Differential Input Select
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As an example, the WM8987L can be set up to convert one differential and one single ended mono signal by applying the differential signal to LINPUT1/RINPUT1 and the single ended signal to RINPUT2. By setting LINSEL to L-R Differential (see Table 4), DS to LINPUT1 - RINPUT1 and RINSEL to RINPUT2, each mono signal can then be routed to a separate ADC or Bypass pat The signal inputs are biased internally to the reference voltage VREF. Whenever the line inputs are muted or the device placed into standby mode, the inputs are kept biased to VREF using special anti-thump circuitry. This reduces any audible clicks that may otherwise be heard when changing inputs.
DC MEASUREMENT
For DC measurements (for example, battery voltage monitoring), the input signal at the LINPUT1 and/or RINPUT1 pins can be taken directly into the respective ADC, bypassing both PGA and microphone boost. The ADC output then becomes unsigned relative to AVDD, instead of being a signed (two's complement) number relative to VREF. Setting L/RDCM will override L/RINSEL. The input range for dc measurement is AGND to AVDD. REGISTER ADDRESS R32 (20h) ADC Signal Path Control (Left) BIT 7:6 LABEL LINSEL DEFAULT 00 DESCRIPTION Left Channel Input Select 00 = LINPUT1 01 = LINPUT2 10 = Reserved 11 = L-R Differential (either LINPUT1RINPUT1 or LINPUT2-RINPUT2, selected by DS) Left Channel Microphone Gain Boost 00 = Boost off (bypassed) 01 = 13dB boost 10 = 20dB boost 11 = 29dB boost Right Channel Input Select 00 = RINPUT1 01 = RINPUT2 10 = Reserved 11 = L-R Differential (either LINPUT1RINPUT1 or LINPUT2-RINPUT2, selected by DS) Right Channel Microphone Gain Boost 00 = Boost off (bypassed) 01 = 13dB boost 10 = 20dB boost 11 = 29dB boost
5:4
LMICBOOST
00
R33 (21h) ADC Signal Path Control (Right)
7:6
RINSEL
00
5:4
RMICBOOST
00
Table 4 Input Software Control REGISTER ADDRESS R31 (1Fh) ADC input Mode BIT 5 LABEL RDCM DEFAULT 0 DESCRIPTION Right Channel DC Measurement 0 = Normal Operation, PGA Enabled 1 = Measure DC level on RINPUT1 Left Channel DC Measurement 0 = Normal Operation, PGA Enabled 1 = Measure DC level on LINPUT1
4
LDCM
0
Table 5 DC Measurement Select
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MONO MIXING
Pre-Production
The stereo ADC can operate as a stereo or mono device, or the two channels can be mixed to mono, either in the analogue domain (i.e. before the ADC) or in the digital domain (after the ADC). MONOMIX selects the mode of operation. For analogue mono mix either the left or right channel ADC can be used, allowing the unused ADC to be powered off or used for a dc measurement conversion. The user also has the flexibility to select the data output from the audio interface using DATSEL. The default is for left and right channel ADC data to be output, but the interface may also be configured so that e.g. left channel ADC data is output as both left and right data for when an analogue mono mix is selected. Note: If DC measurement is selected this overrides the MONOMIX selection. REGISTER ADDRESS R31 (1Fh) ADC input Mode BIT 7:6 LABEL MONOMIX [1:0] DEFAULT 00 DESCRIPTION 00: Stereo 01: Analogue Mono Mix (using left ADC) 10: Analogue Mono Mix (using right ADC) 11: Digital Mono Mix
Table 6 Mono Mixing
REGISTER ADDRESS R23 (17h) Additional Control (1)
BIT 3:2
LABEL DATSEL [1:0]
DEFAULT 00
DESCRIPTION 00: left data=left ADC; right data =right ADC 01: left data =left ADC; right data = left ADC 10: left data = right ADC; right data =right ADC 11: left data = right ADC; right data = left ADC
Table 7 ADC Data Output Configuration The MICBIAS output provides a low noise reference voltage suitable for biasing electret type microphones and the associated external resistor biasing network. Refer to the Applications Information section for recommended external components. The output can be enabled or disabled using the MICB control bit (see also the "Power Management" section). REGISTER ADDRESS R25 (19h) Power Management (1) BIT 1 LABEL MICB DEFAULT 0 DESCRIPTION Microphone Bias Enable 0 = OFF (high impedance output) 1 = ON
Table 8 Microphone Bias Control The internal MICBIAS circuitry is shown below. Note that this is a maximum source current capability for MICBIAS is 3mA. The external biasing resistors therefore must be large enough to limit the MICBIAS current to 3mA.
VMID internal resistor
MICB
MICBIAS = 1.8 x VMID = 0.9 X AVDD
internal resistor
AGND
Figure 8 Microphone Bias Schematic
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PGA CONTROL
The PGA matches the input signal level to the ADC input range. The PGA gain is logarithmically adjustable from +30dB to -17.25dB in 0.75dB steps. Each PGA can be controlled either by the user or by the ALC function (see "Automatic Level Control"). When ALC is enabled for one or both channels, then writing to the corresponding PGA control register has no effect. The gain is independently adjustable on both Right and Left Line Inputs. Additionally, by controlling the register bits LIVU and RIVU, the left and right gain settings can be simultaneously updated. Setting the LZCEN and RZCEN bits enables a zero-cross detector which ensures that PGA gain changes only occur when the signal is at zero, eliminating any zipper noise. If zero cross is enabled a timeout is also available to update the gain if a zero cross does not occur. This function may be enabled by setting TOEN in register R23 (17h). The inputs can also be muted in the analogue domain under software control. The software control registers are shown in Table 9. If zero crossing is enabled, it is necessary to enable zero cross timeout to un-mute the input PGAs. This is because their outputs will not cross zero when muted. Alternatively, zero cross can be disabled before sending the un-mute command. REGISTER ADDRESS R0 (00h) Left Channel PGA 8 BIT LABEL LIVU DEFAULT 0 DESCRIPTION Left Volume Update 0 = Store LINVOL in intermediate latch (no gain change) 1 = Update left and right channel gains (left = LINVOL, right = intermediate latch) Left Channel Input Analogue Mute 1 = Enable Mute 0 = Disable Mute Note: LIVU must be set to un-mute. Left Channel Zero Cross Detector 1 = Change gain on zero cross only 0 = Change gain immediately Left Channel Input Volume Control 111111 = +30dB 111110 = +29.25dB . . 0.75dB steps down to 000000 = -17.25dB Right Volume Update 0 = Store RINVOL in intermediate latch (no gain change) 1 = Update left and right channel gains (right = RINVOL, left = intermediate latch) Right Channel Input Analogue Mute 1 = Enable Mute 0 = Disable Mute Note: RIVU must be set to un-mute. Right Channel Zero Cross Detector 1 = Change gain on zero cross only 0 = Change gain immediately Right Channel Input Volume Control 111111 = +30dB 111110 = +29.25dB . . 0.75dB steps down to 000000 = -17.25dB Timeout Enable 0 : Timeout Disabled 1 : Timeout Enabled
7
LINMUTE
1
6
LZCEN
0
5:0
LINVOL [5:0]
010111 ( 0dB )
R1 (01h) Right Channel PGA
8
RIVU
0
7
RINMUTE
1
6
RZCEN
0
5:0
RINVOL [5:0]
010111 ( 0dB )
R23 (17h) Additional Control (1)
0
TOEN
0
Table 9 Input PGA Software Control
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ANALOGUE TO DIGITAL CONVERTER (ADC)
Pre-Production
The WM8987L uses a multi-bit, oversampled sigma-delta ADC for each channel. The use of multi-bit feedback and high oversampling rates reduces the effects of jitter and high frequency noise. The ADC Full Scale input level is proportional to AVDD. With a 3.3V supply voltage, the full scale level is 1.0 Volts r.m.s. Any voltage greater than full scale may overload the ADC and cause distortion.
ADC DIGITAL FILTER
The ADC filters perform true 24 bit signal processing to convert the raw multi-bit oversampled data from the ADC to the correct sampling frequency to be output on the digital audio interface. The digital filter path is illustrated in Figure 9.
FROM ADC
DIGITAL DECIMATOR
DIGITAL FILTER
DIGITAL HPF
TO DIGITAL AUDIO INTERFACE
ADCHPD
Figure 9 ADC Digital Filter The ADC digital filters contain a digital high pass filter, selectable via software control. The high-pass filter response is detailed in the Digital Filter Characteristics section. When the high-pass filter is enabled the dc offset is continuously calculated and subtracted from the input signal. By setting HPOR, the last calculated dc offset value is stored when the high-pass filter is disabled and will continue to be subtracted from the input signal. If the DC offset is changed, the stored and subtracted value will not change unless the high-pass filter is enabled. This feature can be used for calibration purposes. In addition the high pass filter may be enabled separately on the left and right channels (see Table 11). The output data format can be programmed by the user to accommodate stereo or monophonic recording on both inputs. The polarity of the output signal can also be changed under software control. The software control is shown in Table 10.
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REGISTER ADDRESS R5 (05h) ADC and DAC Control BIT 6:5 LABEL ADCPOL [1:0] DEFAULT 00 DESCRIPTION 00 = Polarity not inverted 01 = L polarity invert 10 = R polarity invert 11 = L and R polarity invert Store dc offset when high-pass filter disabled 1 = store offset 0 = clear offset ADC high-pass filter enable (Digital) HPFLREN = 0 1 = Disable high-pass filter on left and right channels 0 = Enable high-pass filter on left and right channels HPFLREN = 1 0 = High-pass enabled on left, disabled on right 1 = High-pass enabled on right, disabled on left R27 (1Bh) 5 HPFLREN 0 ADC high-pass filter left or right enable 0 = High-pass filter enable/disable on left and right channels controlled by ADCHPD 1 = High-pass filter enabled on left or right channel, as selected by ADCHPD
4
HPOR
0
0
ADCHPD
0
Table 10 ADC Signal Path Control
HPFLREN 0 0 1 1
ADCHPD 0 1 0 1
HIGH PASS MODE High-pass filter enabled on left and right channels High-pass filter disabled on left and right channels High-pass filter enabled on left channel, disabled on right channel High-pass filter disabled on left channel, enabled on right channel
Table 11 ADC High Pass Filter Enable Modes
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DIGITAL ADC VOLUME CONTROL
Pre-Production
The output of the ADCs can be digitally amplified or attenuated over a range from -97dB to +30dB in 0.5dB steps. The volume of each channel can be controlled separately. The gain for a given eight-bit code X is given by: 0.5 x (X-195) dB for 1 X 255; MUTE for X = 0
The LAVU and RAVU control bits control the loading of digital volume control data. When LAVU or RAVU are set to 0, the LADCVOL or RADCVOL control data will be loaded into the respective control register, but will not actually change the digital gain setting. Both left and right gain settings are updated when either LAVU or RAVU are set to 1. This makes it possible to update the gain of both channels simultaneously. REGISTER ADDRESS R21 (15h) Left ADC Digital Volume BIT 7:0 LABEL LADCVOL [7:0] DEFAULT 11000011 ( 0dB ) DESCRIPTION Left ADC Digital Volume Control 0000 0000 = Digital Mute 0000 0001 = -97dB 0000 0010 = -96.5dB ... 0.5dB steps up to 1111 1111 = +30dB Left ADC Volume Update 0 = Store LADCVOL in intermediate latch (no gain change) 1 = Update left and right channel gains (left = LADCVOL, right = intermediate latch) Right ADC Digital Volume Control 0000 0000 = Digital Mute 0000 0001 = -97dB 0000 0010 = -96.5dB ... 0.5dB steps up to 1111 1111 = +30dB Right ADC Volume Update 0 = Store RADCVOL in intermediate latch (no gain change) 1 = Update left and right channel gains (left = intermediate latch, right = RADCVOL)
8
LAVU
0
R22 (16h) Right ADC Digital Volume
7:0
RADCVOL [7:0]
11000011 ( 0dB )
8
RAVU
0
Table 12 ADC Digital Volume Control
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The WM8987L has an automatic level control that aims to keep a constant recording volume irrespective of the input signal level. This is achieved by continuously adjusting the PGA gain so that the signal level at the ADC input remains constant. A digital peak detector monitors the ADC output and changes the PGA gain if necessary. Note that when the ALC function is enabled, the settings of registers 0 and 1 (LINVOL, LIVU, LIZC, LINMUTE, RINVOL, RIVU, RIZC and RINMUTE) are ignored.
AUTOMATIC LEVEL CONTROL (ALC)
input signal
PGA gain
signal after ALC
ALC target level
hold time
decay time
attack time
Figure 10 ALC Operation The ALC function is enabled using the ALCSEL control bits. When enabled, the recording volume can be programmed between -6dB and -28.5dB (relative to ADC full scale) using the ALCL register bits. An upper limit for the PGA gain can be imposed by setting the MAXGAIN control bits. HLD, DCY and ATK control the hold, decay and attack times, respectively: Hold time is the time delay between the peak level detected being below target and the PGA gain beginning to ramp up. It can be programmed in power-of-two (2n) steps, e.g. 2.67ms, 5.33ms, 10.67ms etc. up to 43.7s. Alternatively, the hold time can also be set to zero. The hold time only applies to gain ramp-up, there is no delay before ramping the gain down when the signal level is above target. Decay (Gain Ramp-Up) Time is the time that it takes for the PGA gain to ramp up across 90% of its range (e.g. from -15B up to 27.75dB). The time it takes for the recording level to return to its target value therefore depends on both the decay time and on the gain adjustment required. If the gain adjustment is small, it will be shorter than the decay time. The decay time can be programmed in power-of-two (2n) steps, from 24ms, 48ms, 96ms, etc. to 24.58s. Attack (Gain Ramp-Down) Time is the time that it takes for the PGA gain to ramp down across 90% of its range (e.g. from 27.75dB down to -15B gain). The time it takes for the recording level to return to its target value therefore depends on both the attack time and on the gain adjustment required. If the gain adjustment is small, it will be shorter than the attack time. The attack time can be programmed in power-of-two (2n) steps, from 6ms, 12ms, 24ms, etc. to 6.14s.
When operating in stereo, the peak detector takes the maximum of left and right channel peak values, and any new gain setting is applied to both left and right PGAs, so that the stereo image is preserved. However, the ALC function can also be enabled on one channel only. In this case, only one PGA is controlled by the ALC mechanism, while the other channel runs independently with its PGA gain set through the control register. When one ADC channel is unused or used for DC measurement, the peak detector disregards that channel. The ALC function can also operate when the two ADC outputs are mixed to mono in the digital domain, but not if they are mixed to mono in the analogue domain, before entering the ADCs.
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REGISTER ADDRESS R17 (11h) ALC Control 1 BIT 8:7 LABEL ALCSEL [1:0] DEFAULT 00 (OFF) DESCRIPTION
Pre-Production
ALC function select 00 = ALC off (PGA gain set by register) 01 = Right channel only 10 = Left channel only 11 = Stereo (PGA registers unused) Note: ensure that LINVOL and RINVOL settings (reg. 0 and 1) are the same before entering this mode. Set Maximum Gain of PGA 111 : +30dB 110 : +24dB ....(-6dB steps) 001 : -6dB 000 : -12dB ALC target - sets signal level at ADC input 0000 = -28.5dB FS 0001 = -27.0dB FS ... (1.5dB steps) 1110 = -7.5dB FS 1111 = -6dB FS ALC uses zero cross detection circuit.
6:4
MAXGAIN [2:0]
111 (+30dB)
3:0
ALCL [3:0]
1011 (-12dB)
R18 (12h) ALC Control 2
7
ALCZC
0 (zero cross off) 0000 (0ms)
3:0
HLD [3:0]
ALC hold time before gain is increased. 0000 = 0ms 0001 = 2.67ms 0010 = 5.33ms ... (time doubles with every step) 1111 = 43.691s ALC decay (gain ramp-up) time 0000 = 24ms 0001 = 48ms 0010 = 96ms ... (time doubles with every step) 1010 or higher = 24.58s ALC attack (gain ramp-down) time 0000 = 6ms 0001 = 12ms 0010 = 24ms ... (time doubles with every step) 1010 or higher = 6.14s
R19 (13h) ALC Control 3
7:4
DCY [3:0]
0011 (192ms)
3:0
ATK [3:0]
0010 (24ms)
Table 13 ALC Control Note: The ALC function should not be used when the combined signal gain (mic boost and PGA) is greater than 30dB.
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PEAK LIMITER
To prevent clipping when a large signal occurs just after a period of quiet, the ALC circuit includes a limiter function. If the ADC input signal exceeds 87.5% of full scale (-1.16dB), the PGA gain is ramped down at the maximum attack rate (as when ATK = 0000), until the signal level falls below 87.5% of full scale. This function is automatically enabled whenever the ALC is enabled. Note: If ATK = 0000, then the limiter makes no difference to the operation of the ALC. It is designed to prevent clipping when long attack times are used.
NOISE GATE
When the signal is very quiet and consists mainly of noise, the ALC function may cause "noise pumping", i.e. loud hissing noise during silence periods. The WM8987L has a noise gate function that prevents noise pumping by comparing the signal level at the L/RINPUT1 and/or L/RINPUT2 pins against a noise gate threshold, NGTH. The noise gate cuts in when: * Signal level at ADC [dB] < NGTH [dB] + PGA gain [dB] + Mic Boost gain [dB]
This is equivalent to: * Signal level at input pin [dB] < NGTH [dB]
The ADC output can then either be muted or alternatively, the PGA gain can be held constant (preventing it from ramping up as it normally would when the signal is quiet). The table below summarises the noise gate control register. The NGTH control bits set the noise gate threshold with respect to the ADC full-scale range. The threshold is adjusted in 1.5dB steps. Levels at the extremes of the range may cause inappropriate operation, so care should be taken with set-up of the function. Note that the noise gate only works in conjunction with the ALC function, and always operates on the same channel(s) as the ALC (left, right, both, or none).
REGISTER ADDRESS R20 (14h) Noise Gate Control
BIT 7:3
LABEL NGTH [4:0]
DEFAULT 00000
DESCRIPTION Noise gate threshold 00000 -76.5dBfs 00001 -75dBfs ... 1.5 dB steps 11110 -31.5dBfs 11111 -30dBfs Noise gate type X0 = PGA gain held constant 01 = mute ADC output 11 = reserved (do not use this setting) Noise gate function enable 1 = enable 0 = disable
2:1
NGG [1:0]
00
0
NGAT
0
Table 14 Noise Gate Control Note: The performance of the ADC may degrade at high input signal levels if the monitor bypass mux is selected with MIC boost and ALC enabled.
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3D STEREO ENHANCEMENT
Pre-Production
The WM8987L has a digital 3D enhancement option to artificially increase the separation between the left and right channels. This effect can be used for recording or playback, but not for both simultaneously. Selection of 3D for record or playback is controlled by register bit MODE3D. Important: Switching the 3D filter from record to playback or from playback to record may only be done when ADC and DAC are disabled. The WM8987L control interface will only allow MODE3D to be changed when ADC and DAC are disabled (i.e. bits ADCL, ADCR, DACL and DACR in reg. 26 / 1Ah are all zero). The 3D enhancement function is activated by the 3DEN bit, and has two programmable parameters. The 3DDEPTH setting controls the degree of stereo expansion. Additionally, one of four filter characteristics can be selected for the 3D processing, using the 3DVC and 3DLC control bits. REGISTER ADDRESS R16 (10h) 3D enhance 7 BIT LABEL MODE3D DEFAULT 0 DESCRIPTION Playback/Record 3D select 0 = 3D selected for Record 1 = 3D selected for Playback Upper Cut-off frequency 0 = High (2.2kHz at 48kHz sampling) 1 = Low (1.5kHz at 48kHz sampling) Lower Cut-off frequency 0 = Low (200Hz at 48kHz sampling) 1 = High (500Hz at 48kHz sampling) Stereo depth 0000: 0% (minimum 3D effect) 0001: 6.67% .... 1110: 93.3% 1111: 100% (maximum 3D effect) 3D function enable 1: enabled 0: disabled
6
3DUC
0
5
3DLC
0
4:1
3DDEPTH [3:0]
0000
0
3DEN
0
Table 15 3D Stereo Enhancement Function When 3D enhancement is enabled (and/or the graphic equaliser for playback) it may be necessary to attenuate the signal by 6dB to avoid limiting. This is a user selectable function, enabled by setting ADCDIV2 for the record path and DACDIV2 for the playback path.
REGISTER ADDRESS R5 (05h) ADC and DAC control 8
BIT
LABEL ADCDIV2
DEFAULT 0
DESCRIPTION ADC 6dB attenuate enable 0 = disabled (0dB) 1 = -6dB enabled DAC 6dB attenuate enable 0 = disabled (0dB) 1 = -6dB enabled
7
DACDIV2
0
Table 16 ADC and DAC 6dB Attenuation Select
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The WM8987L output signal paths consist of digital filters, DACs, analogue mixers and output drivers. The digital filters and DACs are enabled when the WM8987L is in `playback only' or `record and playback' mode. The mixers and output drivers can be separately enabled by individual control bits (see Analogue Outputs). Thus it is possible to utilise the analogue mixing and amplification provided by the WM8987L, irrespective of whether the DACs are running or not. The WM8987L receives digital input data on the DACDAT pin. The digital filter block processes the data to provide the following functions: * * * Digital volume control Graphic equaliser and Dynamic Bass Boost Sigma-Delta Modulation
OUTPUT SIGNAL PATH
Two high performance sigma-delta audio DACs convert the digital data into two analogue signals (left and right). These can then be mixed with analogue signals from the L/RINPUT1 and L/RINPUT2 pins, and the mix is fed to the output drivers, ROUT1, LOUT2/ROUT2 and OUT3.
DIGITAL DAC VOLUME CONTROL
The signal volume from each DAC can be controlled digitally, in the same way as the ADC volume (see Digital ADC Volume Control). The gain and attenuation range is -127dB to 0dB in 0.5dB steps. The level of attenuation for an eight-bit code X is given by: 0.5 x (X-255) dB for 1 X 255; MUTE for X = 0
The LDVU and RDVU control bits control the loading of digital volume control data. When LDVU or RDVU are set to 0, the LDACVOL or RDACVOL control data is loaded into an intermediate register, but the actual gain does not change. Both left and right gain settings are updated simultaneously when either LDVU or RDVU are set to 1.
REGISTER ADDRESS R10 (0Ah) Left Channel Digital Volume
BIT 8
LABEL LDVU
DEFAULT 0
DESCRIPTION Left DAC Volume Update 0 = Store LDACVOL in intermediate latch (no gain change) 1 = Update left and right channel gains (left = LDACVOL, right = intermediate latch) Left DAC Digital Volume Control 0000 0000 = Digital Mute 0000 0001 = -127dB 0000 0010 = -126.5dB ... 0.5dB steps up to 1111 1111 = 0dB Right DAC Volume Update 0 = Store RDACVOL in intermediate latch (no gain change) 1 = Update left and right channel gains (left = intermediate latch, right = RDACVOL) Right DAC Digital Volume Control similar to LDACVOL
7:0
LDACVOL [7:0]
11111111 ( 0dB )
R11 (0Bh) Right Channel Digital Volume
8
RDVU
0
7:0
RDACVOL [7:0]
11111111 ( 0dB )
Table 17 Digital Volume Control
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GRAPHIC EQUALISER
Pre-Production
The WM8987L has a digital graphic equaliser and adaptive bass boost function. This function operates on digital audio data before it is passed to the audio DACs. Bass enhancement can take two different forms: * Linear bass control: bass signals are amplified or attenuated by a user programmable gain. This is independent of signal volume, and very high bass gains on loud signals may lead to signal clipping. Adaptive bass boost: The bass volume is amplified by a variable gain. When the bass volume is low, it is boosted more than when the bass volume is high. This method is recommended because it prevents clipping, and usually sounds more pleasant to the human ear.
*
Treble control applies a user programmable gain, without any adaptive boost function. Bass and treble control are completely independent with separately programmable gains and filter characteristics. REGISTER ADDRESS R12 (0Ch) Bass Control BIT 7 LABEL BB 0 DEFAULT DESCRIPTION Bass Boost 0 = Linear bass control 1 = Adaptive bass boost Bass Filter Characteristic 0 = Low Cutoff (130Hz at 48kHz sampling) 1 = High Cutoff (200Hz at 48kHz sampling) Bass Intensity Code 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 R13 (0Dh) Treble Control 6 TC 0 BB=0 +9dB +9dB +7.5dB +6dB +4.5dB +3dB +1.5dB 0dB -1.5dB -3dB -4.5dB -6dB -6dB -6dB -6dB Bypass (OFF) BB=1 15 (max) 14 13 12 11 10 9 8 7 6 5 4 3 2 1
6
BC
0
3:0
BASS [3:0]
1111 (Disabled)
Treble Filter Characteristic 0 = High Cutoff (8kHz at 48kHz sampling) 1 = Low Cutoff (4kHz at 48kHz sampling) Treble Intensity 0000 or 0001 = +9dB 0010 = +7.5dB ... (1.5dB steps) 1011 to 1110 = -6dB 1111 = Disable
3:0
TRBL [3:0]
1111 (Disabled)
Table 18 Graphic Equaliser
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DIGITAL TO ANALOGUE CONVERTER (DAC)
After passing through the graphic equaliser filters, digital `de-emphasis' can be applied to the audio data if necessary (e.g. when the data comes from a CD with pre-emphasis used in the recording). De-emphasis filtering is available for sample rates of 48kHz, 44.1kHz and 32kHz. The WM8987L also has a Soft Mute function, which gradually attenuates the volume of the digital signal to zero. When removed, the gain will return to the original setting. This function is enabled by default. To play back an audio signal, it must first be disabled by setting the DACMU bit to zero. REGISTER ADDRESS R5 (05h) ADC and DAC Control BIT 2:1 LABEL DEEMP [1:0] DEFAULT 00 DESCRIPTION De-emphasis Control 11 = 48kHz sample rate 10 = 44.1kHz sample rate 01 = 32kHz sample rate 00 = No De-emphasis Digital Soft Mute 1 = mute 0 = no mute (signal active)
3
DACMU
1
Table 19 DAC Control The digital audio data is converted to oversampled bit streams in the on-chip, true 24-bit digital interpolation filters. The bitstream data enters two multi-bit, sigma-delta DACs, which convert them to high quality analogue audio signals. The multi-bit DAC architecture reduces high frequency noise and sensitivity to clock jitter. It also uses a Dynamic Element Matching technique for high linearity and low distortion. In normal operation, the left and right channel digital audio data is converted to analogue in two separate DACs. However, it is also possible to disable one channel, so that the same signal (left or right) appears on both analogue output channels. Additionally, there is a mono-mix mode where the two audio channels are mixed together digitally and then converted to analogue using only one DAC, while the other DAC is switched off. The mono-mix signal can be selected to appear on both analogue output channels. The DAC output defaults to non-inverted. Setting DACINV will invert the DAC output phase on both left and right channels. REGISTER ADDRESS R23 (17h) Additional Control (1) BIT 5:4 LABEL DMONOMIX [1:0] DEFAULT 00 DESCRIPTION DAC mono mix 00: stereo 01: mono ((L+R)/2) into DACL, `0' into DACR 10: mono ((L+R)/2) into DACR, `0' into DACL 11: mono ((L+R)/2) into DACL and DACR DAC phase invert 0 : non-inverted 1 : inverted
1
DACINV
0
Table 20 DAC Mono Mix and Phase Invert Select
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OUTPUT MIXERS
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The WM8987L provides the option to mix the DAC output signal with analogue line-in signals from the L/RINPUT1/2, RINPUT1/2 pins or a mono differential input (LINPUT1 - RINPUT1 or LINPUT2 - RINPUT2), selected by DS (see Table 3). The level of the mixed-in signals can be controlled with PGAs (Programmable Gain Amplifiers). The mono mixer is designed to allow a number of signal combinations to be mixed, including the possibility of mixing both the right and left channels together to produce a mono output. To prevent overloading of the mixer when full-scale DAC left and right signals are input, the mixer inputs from the DAC outputs each have a fixed gain of -6dB. The bypass path inputs to the mono mixer have variable gain as determined by R38/R39 bits [6:4]. REGISTER ADDRESS R34 (22h) Left Mixer (1) BIT 2:0 LABEL LMIXSEL DEFAULT 000 DESCRIPTION Left Input Selection for Output Mix 000 = LINPUT1 001 = LINPUT2 011 = Left ADC Input (after PGA / MICBOOST) 100 = Differential input Other settings : Reserved Right Input Selection for Output Mix 000 = RINPUT1 001 = RINPUT2 011 = Right ADC Input (after PGA / MICBOOST) 100 = Differential input Other settings : Reserved
R36 (24h) Right Mixer (1)
2:0
RMIXSEL
000
Table 21 Output Mixer Signal Selection
REGISTER ADDRESS R34 (22h) Left Mixer Control (1)
BIT 8
LABEL LD2LO
DEFAULT 0
DESCRIPTION Left DAC to Left Mixer 0 = Disable (Mute) 1 = Enable Path LMIXSEL Signal to Left Mixer 0 = Disable (Mute) 1 = Enable Path LMIXSEL Signal to Left Mixer Volume 000 = +6dB ... (3dB steps) 111 = -15dB Right DAC to Left Mixer 0 = Disable (Mute) 1 = Enable Path RMIXSEL Signal to Left Mixer 0 = Disable (Mute) 1 = Enable Path RMIXSEL Signal to Left Mixer Volume 000 = +6dB ... (3dB steps) 111 = -15dB
7
LI2LO
0
6:4
LI2LOVOL [2:0]
101 (-9dB)
R35 (23h) Left Mixer Control (2)
8
RD2LO
0
7
RI2LO
0
6:4
RI2LOVOL [2:0]
101 (-9dB)
Table 22 Left Output Mixer Control
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REGISTER ADDRESS R36 (24h) Right Mixer Control (1) BIT 8 LABEL LD2RO DEFAULT 0 DESCRIPTION Left DAC to Right Mixer 0 = Disable (Mute) 1 = Enable Path LMIXSEL Signal to Right Mixer 0 = Disable (Mute) 1 = Enable Path LMIXSEL Signal to Right Mixer Volume 000 = +6dB ... (3dB steps) 111 = -15dB Right DAC to Right Mixer 0 = Disable (Mute) 1 = Enable Path RMIXSEL Signal to Right Mixer 0 = Disable (Mute) 1 = Enable Path RMIXSEL Signal to Right Mixer Volume 000 = +6dB ... (3dB steps) 111 = -15dB
7
LI2RO
0
6:4
LI2ROVOL [2:0]
101 (-9dB)
R37 (25h) Right Mixer Control (2)
8
RD2RO
0
7
RI2RO
0
6:4
RI2ROVOL [2:0]
101 (-9dB)
Table 23 Right Output Mixer Control The mono mixer differs from the left and right mixers in that the signal from each DAC into the mono mixer is attenuated by 6dB. This is to prevent overloading when left and right DAC signals are mixed to mono. When driving a BTL headset as shown in Figure 46, MONOVOL should be set 6dB higher than the other output gains, in order to compensate for the 6dB attenuation at the mono mixer. REGISTER ADDRESS R38 (26h) Mono Mixer Control (1) BIT 8 LABEL LD2MO DEFAULT 0 DESCRIPTION Left DAC to Mono Mixer 0 = Disable (Mute) 1 = Enable Path (-6dB gain) LMIXSEL Signal to Mono Mixer 0 = Disable (Mute) 1 = Enable Path LMIXSEL Signal to Mono Mixer Volume 000 = +6dB ... (3dB steps) 111 = -15dB Right DAC to Mono Mixer 0 = Disable (Mute) 1 = Enable Path RMIXSEL Signal to Mono Mixer 0 = Disable (Mute) 1 = Enable Path RMIXSEL Signal to Mono Mixer Volume 000 = +6dB ... (3dB steps) 111 = -15dB
7
LI2MO
0
6:4
LI2MOVOL [2:0]
101 (-9dB)
R39 (27h) Mono Mixer Control (2)
8
RD2MO
0
7
RI2MO
0
6:4
RI2MOVOL [2:0]
101 (-9dB)
Table 24 Mono Mixer Control
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ANALOGUE OUTPUTS
ROUT1 OUTPUT
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ROUT1 is the non-inverting left-channel output for BTL headsets (see page 53). It can drive 16 or 32 transducer loads. The ROUT1 signal volume can be adjusted under software control by writing to ROUT1VOL. Note that gains over 0dB may cause clipping if the signal is large. Any gain setting below 0101111 (minimum) mutes the output driver. The ROUT1 pin then remains at the same DC level (the reference voltage on the VREF pin), so that no click noise is produced when muting or unmuting. A zero cross detect on the analogue output may also be enabled when changing the gain setting to minimize audible clicks and zipper noise as the gain updates. A timeout is also available to update the gain in the case that zero cross detection is enabled but no zero crossing occurs. This function may be enabled by setting TOEN in register R23 (17h). REGISTER ADDRESS R3 (03h) ROUT1 Volume BIT 8 LABEL RO1VU DEFAULT 0 DESCRIPTION ROUT1VOL Update For any change to ROUT1VOL to take effect, write `1' to this bit. Right zero cross enable 1 = Change gain on zero cross only 0 = Change gain immediately ROUT1 Volume 1111111 = +6dB ... (80 steps) 0110000 = -67dB 0101111 to 0000000 = Analogue MUTE
7
RO1ZC
0
6:0
ROUT1VOL [6:0]
1111001
Table 25 ROUT1 Volume Control
LOUT2/ROUT2 OUTPUTS
LOUT2 and ROUT2 are analogue output pins similar to ROUT1. For BTL headsets, LOUT2 is the non-inverting left output and ROUT2 the inverting right output (with ROUT2INV=1); for single-ended headsets, LOUT2 is the left output and ROUT2 the right output. REGISTER ADDRESS R40 (28h) LOUT2 Volume BIT 6:0 LABEL LOUT2VOL [6:0] DEFAULT 1111001 (0dB) DESCRIPTION LOUT2 volume 1111111 = +6dB ... (80 steps) 0110000 = -67dB 0101111 to 0000000 = Analogue MUTE Left zero cross enable 1 = Change gain on zero cross only 0 = Change gain immediately LOUT2 Volume Update 0 = Store LOUT2VOL in intermediate latch (no gain change) 1 = Update gain for both channels (left=LOUT2VOL, right=from intermediate latch)
7
LO2ZC
0
8
LO2VU
0
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WM8987L
DESCRIPTION ROUT2 volume 1111111 = +6dB ... (80 steps) 0110000 = -67dB 0101111 to 0000000 = Analogue MUTE Left zero cross enable 1 = Change gain on zero cross only 0 = Change gain immediately ROUT2 Volume Update 0 = Store ROUT2VOL in intermediate latch (no gain change) 1 = Update gain for both channels (right=ROUT2VOL, left=from intermediate latch) ROUT2 Invert 0 = No Inversion (0 phase shift) 1 = Signal inverted (180 phase shift)
7
RO2ZC
0
8
RO2VU
0
R24 (18h) Additional Control (2)
4
ROUT2INV
0
Table 26 LOUT2/ROUT2 Volume Control For single-ended operation, the LO2VU and RO2VU bits provide a method to ensure that the left and right channel gains are updated at the same time (irrespective of the time delay between writing to registers R40 and R41).
OUT3 OUTPUT
The OUT3 pin can drive a 16 or 32 headphone or be used as a DC reference for a capless headphone output (see page 55). OUT3SW selects the mode of operation required. REGISTER ADDRESS R24 (18h) Additional Control (2) BIT 8 LABEL OUT3SW DEFAULT 0 DESCRIPTION OUT3 select 0 : VREF 1 : mono mixer (volume controlled by MONOVOL)
Table 27 OUT3 Select When OUT3SW=1, OUT3 drives out the inverted signal from the mono mixer. In this case, the mono mixer should be enabled (MONO=1 in R26). The signal amplitude at the OUT3 output can be adjusted under software control by writing to MONOVOL in R42. REGISTER ADDRESS R42 (2Ah) Mono mixer Volume BIT 6:0 LABEL MONOVOL [6:0] DEFAULT 1111001 (0dB) DESCRIPTION Mono Mixer Volume 1111111 = +6dB ... (80 steps) 0110000 = -67dB 0101111 to 0000000 = Analogue MUTE Mono Mixer zero cross enable 1 = Change gain on zero cross only 0 = Change gain immediately
7
MOZC
0
Table 28 Mono Mixer Volume Control
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ENABLING THE OUTPUTS
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The analogue outputs and output mixers of the WM8987L can be separately enabled or disabled as shown in Table 29. REGISTER ADDRESS R26 (1Ah) Power Management (2) BIT 5 4 3 2 1 LABEL ROUT1 LOUT2 ROUT2 MONO OUT3 0 0 0 0 0 DEFAULT DESCRIPTION Enables ROUT1 and right mixer Enables LOUT2 and left mixer Enables ROUT2 and right mixer Enable mono mixer Enables OUT3
Note: All "Enable" bits are 1 = ON, 0 = OFF Table 29 Analogue Output Control All outputs and mixers are disabled by default. To save power, they should remain disabled whenever possible. Outputs can be enabled at any time, except when VREF is disabled (VR=0), as this may cause pop noise (see "Power Management" and "Applications Information" sections). Whenever an analogue output is disabled, it remains connected to the VREF voltage through an internal resistor. This helps to prevent pop noise when the output is re-enabled. The resistance between VREF and each output can be controlled using the VROI bit in register 27. The default is low (1.5k), so that any capacitors on the outputs can charge up quickly at start-up. If a high impedance is desired for disabled outputs, VROI can then be set to 1, increasing the resistance to about 40k. REGISTER ADDRESS R27 (1Bh) Additional (1) BIT 6 LABEL VROI 0 DEFAULT DESCRIPTION VREF to analogue output resistance 0: 1.5 k 1: 40 k
Table 30 Disabled Outputs to VREF Resistance
THERMAL SHUTDOWN
The analogue outputs can drive large currents. To protect the WM8987L from overheating, a thermal shutdown circuit is included. If the device temperature reaches approximately 1500C and the thermal shutdown circuit is enabled (TSDEN = 1) then the output amplifiers (pins ROUT1, LOUT2, ROUT2 and OUT3) are disabled. REGISTER ADDRESS R23 (17h) Additional Control (1) BIT 8 LABEL TSDEN 0 DEFAULT DESCRIPTION Thermal Shutdown Enable 0 : thermal shutdown disabled 1 : thermal shutdown enabled
Table 31 Thermal Shutdown
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DIGITAL AUDIO INTERFACE
The digital audio interface is used for inputting DAC data into the WM8987L and outputting ADC data from it. It uses five pins: * * * * ADCDAT: ADC data output ADCLRC: ADC data alignment clock DACDAT: DAC data input DACLRC: DAC data alignment clock
* BCLK: Bit clock, for synchronisation The clock signals BCLK, ADCLRC and DACLRC can be outputs when the WM8987L operates as a master, or inputs when it is a slave (see Master and Slave Mode Operation, below). Three different audio data formats are supported: * * * I 2S DSP mode Left justified
All of these modes are MSB first. They are described in Audio Data Formats, below. Refer to the Electrical Characteristic section for timing information.
MASTER AND SLAVE MODE OPERATION
The WM8987L can be configured as either a master or slave mode device. As a master device the WM8987L generates BCLK, ADCLRC and DACLRC and thus controls sequencing of the data transfer on ADCDAT and DACDAT. In slave mode, the WM8987L responds with data to clocks it receives over the digital audio interface. The mode can be selected by writing to the MS bit (see Table 23). Master and slave modes are illustrated below.
Figure 11 Master Mode
Figure 12 Slave Mode
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AUDIO DATA FORMATS
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In Left Justified mode, the MSB is available on the first rising edge of BCLK following a LRCLK transition. The other bits up to the LSB are then transmitted in order. Depending on word length, BCLK frequency and sample rate, there may be unused BCLK cycles before each LRCLK transition.
Figure 13 Left Justified Audio Interface (assuming n-bit word length) In I2S mode, the MSB is available on the second rising edge of BCLK following a LRCLK transition. The other bits up to the LSB are then transmitted in order. Depending on word length, BCLK frequency and sample rate, there may be unused BCLK cycles between the LSB of one sample and the MSB of the next.
Figure 14 I2S Justified Audio Interface (assuming n-bit word length) In DSP/PCM mode, the left channel MSB is available on either the 1st (mode B) or 2nd (mode A) rising edge of BCLK (selectable by LRP) following a rising edge of LRC. Right channel data immediately follows left channel data. Depending on word length, BCLK frequency and sample rate, there may be unused BCLK cycles between the LSB of the right channel data and the next sample. In device master mode, the LRC output will resemble the frame pulse shown in Figure 15 and Figure 16. In device slave mode, Figure 17 and Figure 18, it is possible to use any length of frame pulse less than 1/fs, providing the falling edge of the frame pulse occurs greater than one BCLK period before the rising edge of the next frame pulse.
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Figure 15 DSP/PCM Mode Audio Interface (mode A, LRP=0, Master)
Figure 16 DSP/PCM Mode Audio Interface (mode B, LRP=1, Master)
Figure 17 DSP/PCM Mode Audio Interface (mode A, LRP=0, Slave)
Figure 18 DSP/PCM Mode Audio Interface (mode B, LRP=0, Slave)
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AUDIO INTERFACE CONTROL
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The register bits controlling audio format, word length and master / slave mode are summarised in Table 32. MS selects audio interface operation in master or slave mode. In Master mode BCLK, ADCLRC and DACLRC are outputs. The frequency of ADCLRC and DACLRC is set by the sample rate control bits SR[4:0] and USB. In Slave mode BCLK, ADCLRC and DACLRC are inputs. REGISTER ADDRESS R7 (07h) Digital Audio Interface Format BIT 6 MS LABEL DEFAULT 0 DESCRIPTION Master / Slave Mode Control 1 = Enable Master Mode 0 = Enable Slave Mode Left/Right channel swap 1 = swap left and right DAC data in audio interface 0 = output left and right data as normal right, left and i2s modes - LRCLK polarity 1 = invert LRCLK polarity 0 = normal LRCLK polarity DSP Mode - mode A/B select 1 = MSB is available on 1st BCLK rising edge after LRC rising edge (mode B) 0 = MSB is available on 2nd BCLK rising edge after LRC rising edge (mode A) 3:2 WL[1:0] 10 Audio Data Word Length 11 = 32 bits (see Note) 10 = 24 bits 01 = 20 bits 00 = 16 bits Audio Data Format Select 11 = DSP Mode 10 = I2S Format 01 = Left justified 00 = Reserved
5
LRSWAP
0
4
LRP
0
1:0
FORMAT[1:0]
10
Table 32 Audio Data Format Control
AUDIO INTERFACE OUTPUT TRISTATE
Register bit TRI, register 24(18h) bit[3] can be used to tristate the ADCDAT pin and switch ADCLRC, DACLRC and BCLK to inputs. In Slave mode (MASTER=0) ADCLRC, DACLRC and BCLK are by default configured as inputs and only ADCDAT will be tri-stated, (see Table 33). REGISTER ADDRESS R24(18h) Additional Control (2) BIT 3 LABEL TRI DEFAULT 0 DESCRIPTION Tristates ADCDAT and switches ADCLRC, DACLRC and BCLK to inputs. 0 = ADCDAT is an output, ADCLRC, DACLRC and BCLK are inputs (slave mode) or outputs (master mode) 1 = ADCDAT is tristated, ADCLRC, DACLRC and BCLK are inputs
Table 33 Tri-stating the Audio Interface
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MASTER MODE ADCLRC AND DACLRC ENABLE
In Master mode, by default ADCLRC is disabled when the ADC is disabled and DACLRC is disabled when the DAC is disabled. Register bit LRCM, register 24(18h) bit[2] changes the control so that the ADCLRC and DACLRC are disabled only when ADC and DAC are disabled. This enables the user to use e.g. ADCLRC for both ADC and DAC LRCLK and disable the ADC when DAC only operation is required, (see Table 34). REGISTER ADDRESS R24(18h) Additional Control (2) BIT 2 LABEL LRCM DEFAULT 0 DESCRIPTION Selects disable mode for ADCLRC and DACLRC 0 = ADCLRC disabled when ADC (Left and Right) disabled, DACLRC disabled when DAC (Left and Right) disabled. 1 = ADCLRC and DACLRC disabled only when ADC (Left and Right) and DAC (Left and Right) are disabled.
Table 34 ADCLRC/DACLRC Enable
BIT CLOCK MODE
The default master mode bit clock generator produces a bit clock frequency based on the sample rate and input MCLK frequency as shown in Table 38. When enabled by setting the appropriate BCM[1:0] bits, the bit clock mode (BCM) function overrides the default master mode bit clock generator to produce the bit clock frequency shown in the table below: REGISTER ADDRESS R8 (08h) Clocking and Sample Rate Control BIT 8:7 LABEL BCM[1:0] DEFAULT 00 DESCRIPTION BCLK Frequency 00 = BCM function disabled 01 = MCLK/4 10 = MCLK/8 11 = MCLK/16
Table 35 Master Mode BCLK Frequency Control The BCM mode bit clock generator produces 16 or 24 bit clock cycles per sample. The number of bit clock cycles per sample in this mode is determined by the word length bits (WL[1:0]) in the Digital Audio Interface Format register (R7). When these bits are set to 00, there will be 16 bit clock cycles per sample. When these bits are set to 01, 10 or 11, there will be 24 bit clock cycles per sample. Please refer to Figure 19. The BCM generator uses the ADCLRC signal, hence the ADCLRC signal must be enabled when using bit clock mode. To enable the ADCLRC signal, either the ADC must be powered up or, if the ADC is not in use, the LRCM bit must be set to enable both the ADCLRC and DACLRC signals when either the ADC or the DAC is enabled. When the BCM function is enabled, the following restrictions apply: 1. The DAC and ADC must be operated at the same sample rate. 2. DSP late digital audio interface mode is not available and must not be enabled.
Figure 19 Bit Clock Mode Note: The shaded bit clock cycles are present only when 24-bit mode is selected. Please refer to the "Bit Clock Mode" description for details.
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CLOCK OUTPUT
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By default, the ADCLRC pin is the ADC word clock input/output. Under the control of ADCLRM[1:0], register 27(1Bh) bits [8:7] the ADCLRC pin may be configured as a clock output. If ADCLRM is 01, 10 or 11 then ADCLRC pin is always an output even in slave mode or when TRI = `1', (see Table 36). The ADC then uses the DACLRC pin as its LRCLK in both master and slave modes. REGISTER ADDRESS R27(1Bh) Additional Control (3) BIT LABEL DEFAULT 00 DESCRIPTION Configures ADCLRC pin 00 = ADCLRC is ADC word clock input (slave mode) or ADCLRC output (master mode) 01 = ADCLRC pin is MCLK output 10 = ADCLRC pin is MCLK / 5.5 output 11 = ADCLRC pin is MCLK / 6 output
[8:7] ADCLRM [1:0]
Table 36 ADCLRC Clock Output
CLOCKING AND SAMPLE RATES
The WM8987L supports a wide range of master clock frequencies on the MCLK pin, and can generate many commonly used audio sample rates directly from the master clock. The ADC and DAC do not need to run at the same sample rate; several different combinations are possible. There are two clocking modes: * * `Normal' mode supports master clocks of 128fs, 192fs, 256fs, 384fs, and their multiples (Note: fs refers to the ADC or DAC sample rate, whichever is faster) USB mode supports 12MHz or 24MHz master clocks. This mode is intended for use in systems with a USB interface, and eliminates the need for an external PLL to generate another clock frequency for the audio codec. REGISTER ADDRESS R8 (08h) Clocking and Sample Rate Control 6 BIT LABEL CLKDIV2 0 DEFAULT DESCRIPTION Master Clock Divide by 2 1 = MCLK is divided by 2 0 = MCLK is not divided Sample Rate Control Clocking Mode Select 1 = USB Mode 0 = `Normal' Mode
5:1 0
SR [4:0] USB
00000 0
Table 37 Clocking and Sample Rate Control The clocking of the WM8987L is controlled using the CLKDIV2, USB, and SR control bits. Setting the CLKDIV2 bit divides MCLK by two internally. The USB bit selects between `Normal' and USB mode. Each value of SR[4:0] selects one combination of MCLK division ratios and hence one combination of sample rates (see next page). Since all sample rates are generated by dividing MCLK, their accuracy depends on the accuracy of MCLK. If MCLK changes, the sample rates change proportionately. Note that some sample rates (e.g. 44.1kHz in USB mode) are approximated, i.e. they differ from their target value by a very small amount. This is not audible, as the maximum deviation is only 0.27% (8.0214kHz instead of 8kHz in USB mode). By comparison, a half-tone step corresponds to a 5.9% change in pitch. The SR[4:0] bits must be set to configure the appropriate ADC and DAC sample rates in both master and slave mode.
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ADC SAMPLE RATE (ADCLRC) DAC SAMPLE RATE (DACLRC) USB SR [4:0] FILTER TYPE 1 1 1 1 1 1 1 1 3 1 1 1 1 1 1 3 1 1 1 1 1 1 1 1 3 1 1 1 1 1 1 3 0 0 1 1 1 0 0 1 0 0 1 1 0 0 3 2 BCLK (MS=1) MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/2 MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/2 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/3 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/3 MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK
MCLK CLKDIV2=0 12.288 MHz
MCLK CLKDIV2=1
`Normal' Clock Mode (`*' indicates backward compatibility with WM8731) 8 kHz (MCLK/1536) 8 kHz (MCLK/1536) 24.576 MHz 8 kHz (MCLK/1536) 48 kHz (MCLK/256) 12 kHz (MCLK/1024) 12 kHz (MCLK/1024) 16 kHz (MCLK/768) 16 kHz (MCLK/768) 24 kHz (MCLK/512) 24 kHz (MCLK/512) 32 kHz (MCLK/384) 32 kHz (MCLK/384) 48 kHz (MCLK/256) 8 kHz (MCLK/1536) 48 kHz (MCLK/256) 48 kHz (MCLK/256) 96 kHz (MCLK/128) 96 kHz (MCLK/128) 8.0182 kHz (MCLK/1408) 8.0182 kHz (MCLK/1408) 11.2896MHz 22.5792MHz 8.0182 kHz (MCLK/1408) 44.1 kHz (MCLK/256) 11.025 kHz (MCLK/1024) 11.025 kHz (MCLK/1024) 22.05 kHz (MCLK/512) 22.05 kHz (MCLK/512) 44.1 kHz (MCLK/256) 8.0182 kHz (MCLK/1408) 44.1 kHz (MCLK/256) 44.1 kHz (MCLK/256) 88.2 kHz (MCLK/128) 88.2 kHz (MCLK/128) 8 kHz (MCLK/2304) 8 kHz (MCLK/2304) 18.432MHz 36.864MHz 8 kHz (MCLK/2304) 48 kHz (MCLK/384) 12 kHz (MCLK/1536) 12 kHz (MCLK/1536) 16kHz (MCLK/1152) 16 kHz (MCLK/1152) 24kHz (MCLK/768) 24 kHz (MCLK/768) 32 kHz (MCLK/576) 32 kHz (MCLK/576) 48 kHz (MCLK/384) 48 kHz (MCLK/384) 48 kHz (MCLK/384) 8 kHz (MCLK/2304) 96 kHz (MCLK/192) 96 kHz (MCLK/192) 8.0182 kHz (MCLK/2112) 8.0182 kHz (MCLK/2112) 16.9344MHz 33.8688MHz 8.0182 kHz (MCLK/2112) 44.1 kHz (MCLK/384) 11.025 kHz (MCLK/1536) 11.025 kHz (MCLK/1536) 22.05 kHz (MCLK/768) 22.05 kHz (MCLK/768) 44.1 kHz (MCLK/384) 8.0182 kHz (MCLK/2112) 44.1 kHz (MCLK/384) 44.1 kHz (MCLK/384) 88.2 kHz (MCLK/192) 88.2 kHz (MCLK/192) USB Mode (`*' indicates backward compatibility with WM8731) 8 kHz (MCLK/1500) 8 kHz (MCLK/1500) 12.000MHz 24.000MHz 8 kHz (MCLK/1500) 48 kHz (MCLK/250) 8.0214 kHz (MCLK/1496) 8.0214kHz (MCLK/1496) 8.0214 kHz (MCLK/1496) 44.118 kHz (MCLK/272) 11.0259 kHz (MCLK/1088) 11.0259kHz (MCLK/1088) 12 kHz (MCLK/1000) 12 kHz (MCLK/1000) 16kHz (MCLK/750) 16kHz (MCLK/750) 22.0588kHz (MCLK/544) 22.0588kHz (MCLK/544) 24kHz (MCLK/500) 24kHz (MCLK/500) 32 kHz (MCLK/375) 32 kHz (MCLK/375) 44.118 kHz (MCLK/272) 8.0214kHz (MCLK/1496) 44.118 kHz (MCLK/272) 44.118 kHz (MCLK/272) 48 kHz (MCLK/250) 8 kHz (MCLK/1500) 48 kHz (MCLK/250) 48 kHz (MCLK/250) 88.235kHz (MCLK/136) 88.235kHz (MCLK/136) 96 kHz (MCLK/125) 96 kHz (MCLK/125) Table 38 Master Clock and Sample Rates
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
00110 * 00100 * 01000 01010 11100 01100 * 00010 * 00000 * 01110 * 10110 * 10100 * 11000 11010 10010 * 10000 * 11110 * 00111 * 00101 * 01001 01011 11101 01101 * 00001 * 00011 * 01111 * 10111 * 10101 * 11001 11011 10011 * 10001 * 11111 * 00110 * 00100 * 10111 * 10101 * 11001 01000 01010 11011 11100 01100 * 10011 * 10001 * 00010 * 00000 * 11111 * 01110 *
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CONTROL INTERFACE
SELECTION OF CONTROL MODE
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The WM8987L is controlled by writing to registers through a serial control interface. A control word consists of 16 bits. The first 7 bits (B15 to B9) are address bits that select which control register is accessed. The remaining 9 bits (B8 to B0) are data bits, corresponding to the 9 bits in each control register. The control interface can operate as either a 3-wire or 2-wire MPU interface. The MODE pin selects the interface format. MODE Low High INTERFACE FORMAT 2 wire 3 wire
Table 39 Control Interface Mode Selection
3-WIRE SERIAL CONTROL MODE
In 3-wire mode, every rising edge of SCLK clocks in one data bit from the SDIN pin. A rising edge on CSB latches in a complete control word consisting of the last 16 bits.
latch CSB
SCLK
SDIN
B15
B14
B13
B12
B11
B10
B9
B8
B7
B6
B5
B4
B3
B2
B1
B0
control register address
control register data bits
Figure 20 3-Wire Serial Control Interface
2-WIRE SERIAL CONTROL MODE
The WM8987L supports software control via a 2-wire serial bus. Many devices can be controlled by the same bus, and each device has a unique 7-bit address (this is not the same as the 7-bit address of each register in the WM8987L). The WM8987L operates as a slave device only. The controller indicates the start of data transfer with a high to low transition on SDIN while SCLK remains high. This indicates that a device address and data will follow. All devices on the 2-wire bus respond to the start condition and shift in the next eight bits on SDIN (7-bit address + Read/Write bit, MSB first). If the device address received matches the address of the WM8987L and the R/W bit is `0', indicating a write, then the WM8987L responds by pulling SDIN low on the next clock pulse (ACK). If the address is not recognised or the R/W bit is `1', the WM8987L returns to the idle condition and wait for a new start condition and valid address. Once the WM8987L has acknowledged a correct address, the controller sends the first byte of control data (B15 to B8, i.e. the WM8987L register address plus the first bit of register data). The WM8987L then acknowledges the first data byte by pulling SDIN low for one clock pulse. The controller then sends the second byte of control data (B7 to B0, i.e. the remaining 8 bits of register data), and the WM8987L acknowledges again by pulling SDIN low. The transfer of data is complete when there is a low to high transition on SDIN while SCLK is high. After receiving a complete address and data sequence the WM8987L returns to the idle state and waits for another start condition. If a start or stop condition is detected out of sequence at any point during data transfer (i.e. SDIN changes while SCLK is high), the device jumps to the idle condition.
SDIN
DEVICE ADDRESS (7 BITS)
RD / WR BIT
ACK (LOW)
CONTROL BYTE 1 (BITS 15 TO 8)
ACK (LOW)
CONTROL BYTE 2 (BITS 7 TO 0)
ACK (LOW)
SCLK
START
register address and 1st register data bit
remaining 8 bits of register data
STOP
Figure 21 2-Wire Serial Control Interface
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The WM8987L has two possible device addresses, which can be selected using the CSB pin. CSB STATE Low High DEVICE ADDRESS 0011010 (0 x 34h) 0011011 (0 x 36h)
Table 40 2-Wire MPU Interface Address Selection
POWER SUPPLIES
The WM8987L can use up to four separate power supplies: * AVDD / AGND: Analogue supply, powers all analogue functions except the headphone drivers. AVDD can range from 1.8V to 3.6V and has the most significant impact on overall power consumption (except for power consumed in the headphone). A large AVDD slightly improves audio quality. HPVDD / HPGND: Headphone supply, powers the headphone drivers. HPVDD is normally tied to AVDD, but it requires separate layout and decoupling capacitors to curb harmonic distortion. If HPVDD is lower than AVDD, the output signal may be clipped. DCVDD: Digital core supply, powers all digital functions except the audio and control interfaces. DCVDD can range from 1.42V to 3.6V, and has no effect on audio quality. The return path for DCVDD is DGND, which is shared with DBVDD. DBVDD: Digital buffer supply, powers the audio and control interface buffers. This makes it possible to run the digital core at very low voltages, saving power, while interfacing to other digital devices using a higher voltage. DBVDD draws much less power than DCVDD, and has no effect on audio quality. DBVDD can range from 1.8V to 3.6V. The return path for DBVDD is DGND, which is shared with DCVDD.
*
*
*
It is possible to use the same supply voltage on all four. However, digital and analogue supplies should be routed and decoupled separately to keep digital switching noise out of the analogue signal paths.
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POWER MANAGEMENT
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The WM8987L has two control registers that allow users to select which functions are active. For minimum power consumption, unused functions should be disabled. To avoid any pop or click noise, it is important to enable or disable functions in the correct order (see Applications Information). VMIDSEL is the enable for the VMID reference, which defaults to disabled and can be enabled as a 50k potential divider or, for low power maintenance of VREF when all other blocks are disabled, as a 500k potential divider.
REGISTER ADDRESS R25 (19h) Power Management (1)
BIT 8:7
LABEL VMIDSEL
DEFAULT 00
DESCRIPTION Vmid divider enable and select 00 - Vmid disabled (for OFF mode) 01 - 50k divider enabled (for playback/record) 10 - 500k divider enabled (for low-power standby) 11 - 5k divider enabled (for fast start-up) VREF (necessary for all other functions) Analogue in PGA Left Analogue in PGA Right ADC Left ADC Right MICBIAS DAC Left DAC Right ROUT1 Output Buffer LOUT2 Output Buffer ROUT2 Output Buffer Mono Mixer OUT3 Output Buffer
6 5 4 3 2 1 R26 (1Ah) Power Management (2) 8 7 5 4 3 2 1
VREF AINL AINR ADCL ADCR MICB DACL DACR ROUT1 LOUT2 ROUT2 MONO OUT3
0 0 0 0 0 0 0 0 0 0 0 0 0
Notes: 1. All bits except VMIDSEL are 1=on, 0=off. 2. The left mixer is enabled when LOUT2=1. 3. The right mixer is enabled when ROUT1=1 or ROUT2=1. 4. The mono mixer is enabled when MONO=1. Table 41 Power Management
STOPPING THE MASTER CLOCK
In order to minimise power consumed in the digital core of the WM8987L, the master clock may be stopped in Standby and OFF modes. If this cannot be done externally at the clock source, the DIGENB bit (R25, bit 0) can be set to stop the MCLK signal from propagating into the device core. In Standby mode, setting DIGENB will typically provide an additional power saving on DCVDD of 20uA. However, since setting DIGENB has no effect on the power consumption of other system components external to the WM8987L, it is preferable to disable the master clock at its source wherever possible. REGISTER ADDRESS R25 (19h) Additional Control (1) 0 BIT LABEL DIGENB 0 DEFAULT DESCRIPTION Master clock disable 0: master clock enabled 1: master clock disabled
Table 42 ADC and DAC Oversampling Rate Selection NOTE: Before DIGENB can be set, the control bits ADCL, ADCR, DACL and DACR must be set to zero and a waiting time of 1ms must be observed. Any failure to follow this procedure may prevent DACs and ADCs from re-starting correctly.
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SAVING POWER BY REDUCING OVERSAMPLING RATE
The default mode of operation of the ADC and DAC digital filters is in 128x oversampling mode. Under the control of ADCOSR and DACOSR the oversampling rate may be halved. This will result in a slight decrease in noise performance but will also reduce the power consumption of the device. In USB mode ADCOSR must be set to 0, i.e. 128x oversampling. REGISTER ADDRESS R24 (18h) Additional Control (2) 1 BIT LABEL ADCOSR 0 DEFAULT DESCRIPTION ADC oversample rate select 1 = 64x (lowest power) 0 = 128x (best SNR) DAC oversample rate select 1 = 64x (lowest power) 0 = 128x (best SNR)
0
DACOSR
0
Table 43 ADC and DAC Oversampling Rate Selection ADCOSR set to `1', 64x oversample mode, is not supported in USB mode (USB=1).
SAVING POWER AT HIGHER SUPPLY VOLTAGES
The analogue supplies to the WM8987L can run from 1.8V to 3.6V. By default, all analogue circuitry on the device is optimized to run at 3.3V. This set-up is also good for all other supply voltages down to 1.8V. At lower voltages, performance can be improved by increasing the bias current. If low power operation is preferred the bias current can be left at the default setting. This is controlled as shown below. REGISTER ADDRESS R23 (17h) Additional Control(1) BIT 7:6 LABEL VSEL [1:0] DEFAULT 11 DESCRIPTION Analogue Bias optimization 00: Highest bias current, optimized for AVDD=1.8V 01: Bias current optimized for AVDD=2.5V 1X: Lowest bias current, optimized for AVDD=3.3V
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WM8987L REGISTER MAP
ADDRESS REGISTER (Bit 15 - 9) R0 (00h) R1 (01h) R2 (02h) R3 (03h) R4 (04h) R5 (05h) R6 (06h) R7 (07h) R8 (08h) R9 (09h) R10 (0Ah) R11 (0Bh) R12 (0Ch) R13 (0Dh) R15 (0Fh) R16 (10h) R17 (11h) R18 (12h) R19 (13h) R20 (14h) R21 (15h) R22 (16h) R23 (17h) R24 (18h) R25 (19h) R26 (1Ah) R27 (1Bh) R31 (1Fh) R32 (20h) R33 (21h) R34 (22h) R35 (23h) R36 (24h) R37 (25h) R38 (26h) R39 (27h) R40 (28h) R41 (29h) R42 (2Ah) 0000000 0000001 0000010 0000011 0000100 0000101 0000110 0000111 0001000 0001001 0001010 0001011 0001100 0001101 0001111 0010000 0010001 0010010 0010011 0010100 0010101 0010110 0010111 0011000 0011001 0011010 0011011 0011111 0100000 0100001 0100010 0100011 0100100 0100101 0100110 0100111 0101000 0101001 0101010 Left Input volume Right Input volume Reserved ROUT1 volume Reserved ADC & DAC Control Reserved Audio Interface Sample rate Reserved Left DAC volume Right DAC volume Bass control Treble control Reset 3D control ALC1 ALC2 ALC3 Noise Gate Left ADC volume Right ADC volume Additional control(1) 0 ADCDIV2 DACDIV2 0 0 BCM[1:0] 0 LDVU RDVU 0 0 BB 0 BC TC 0 0 0 0 0 ADCPOL[1:0] 0 MS CLKDIV2 0 0 0 0 LRSWAP RO1VU RO1ZC n/a HPOR 0 LRP DACMU 0 WL[1:0] SR[4:0] 0 0 0 DEEMPH[1:0] 0 0 ADCHPD 0 LIVU RIVU LINMUTE RINMUTE LIZC RIZC n/a ROUT1VOL[6:0] LINVOL RINVOL remarks Bit[8] Bit[7] Bit[6] Bit[5] Bit[4] Bit[3] Bit[2] Bit[1] Bit[0]
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default 010010111 010010111 n/a 001111001 n/a 000001000 000000000 000001010 000000000 000000000 011111111 011111111
page ref 19 19 n/a 32 n/a 19, 26, 29 n/a 38 40 n/a 27 27 28 28 n/a 26 24 24 24 25 22 22 18,19,29,34 33 44 44 35 17 17 17 30 30 31 31 31 31 33 33 33
FORMAT[1:0] USB 0
LDACVOL[7:0] RDACVOL[7:0] 0 0 BASS[3:0] TRBL[3:0]
000001111 000001111 not reset 3DEN 000000000 001111011 000000000 000110010 NGAT 000000000 011000011 011000011
writing to this register resets all registers to their default state MODE3D 3DUC 3DLC MAXGAIN[2:0] 0 DCY[3:0] NGTH[4:0] LADCVOL[7:0] RADCVOL[7:0] VSEL[1:0] 0 0 VREF 0 VROI DMONOMIX[1:0] 0 AINL ROUT1 HPFLREN RDCM ROUT2INV AINR LOUT2 0 LDCM DATSEL[1:0] TRI ADCL ROUT2 0 0 0 0 0 0 0 0 0 0 LOUT2VOL[6:0] ROUT2VOL[6:0] MONOVOL[6:0] 0 0 0 0 LRCM ADCR MONO 0 0 0 0 DACINV ADCOSR MICB OUT3 0 0 0 0 LMIXSEL[2:0] 0 RMIXSEL[2:0] 0 0 0 0 0 0 0 TOEN DACOSR DIGENB 0 0 0 0 0 0 0 3DDEPTH[3:0] ALCL[3:0] HLD[3:0] ATK[3:0] NGG[1:0]
ALCSEL[1:0] 0 0 0 LAVU RAVU TSDEN ALCZC
011000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 001010000 001010000 001010000 001010000 001010000 001010000 001111001 001111001 001111001
Additional control(2) OUT3SW Pwr Mgmt (1) Pwr Mgmt (2) Additional Control (3) ADC input mode ADCL signal path ADCR signal path Left out Mix (1) Left out Mix (2) Right out Mix (1) Right out Mix (2) Mono Mix (1) Mono Mix (2) LOUT2 volume ROUT2 volume Mono mixer volume
VMIDSEL[1:0] DACL DACR
ADCLRM[1:0] DS 0 0 LD2LO RD2LO LD2RO RD2RO LD2MO RD2MO LO2VU RO2VU 0
MONOMIX[1:0] LINSEL[1:0] RINSEL[1:0] LI2LO RI2LO LI2RO RI2RO LI2MO RI2MO LO2ZC RO2ZC MOZC
LMICBOOST[1:0] RMICBOOST[1:0] LI2LOVOL[2:0] RI2LOVOL[2:0] LI2ROVOL[2:0] RI2ROVOL[2:0] LI2MOVOL[2:0] RI2MOVOL[2:0]
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DIGITAL FILTER CHARACTERISTICS
The ADC and DAC employ different digital filters. There are 4 types of digital filter, called Type 0, 1, 2 and 3. The performance of Types 0 and 1 is listed in the table below, the responses of all filters is shown in the proceeding pages.
PARAMETER Passband Passband Ripple Stopband Stopband Attenuation Passband Passband Ripple Stopband Stopband Attenuation High Pass Filter Corner Frequency
TEST CONDITIONS +/- 0.05dB -6dB
MIN 0
TYP
MAX 0.416fs
UNIT
ADC Filter Type 0 (USB Mode, 250fs operation) 0.5fs +/- 0.05 0.584fs f > 0.584fs +/- 0.05dB -6dB 0.5465fs f > 0.5465fs -3dB -0.5dB -0.1dB DAC Filter Type 0 (USB mode, 250fs operation) Passband Passband Ripple Stopband Stopband Attenuation Passband Passband Ripple Stopband Stopband Attenuation Table 44 Digital Filter Characteristics DAC FILTERS Mode 0 (250 USB) 1 (256/272) 2 (250 USB, 96k mode) 3 (256/272, 88.2/96k mode) Group Delay 11/FS 16/FS 4/FS 3/FS Mode 0 (250 USB) 1 (256/272) 2 (250 USB, 96k mode) 3 (256/272, 88.2/96k mode) ADC FILTERS Group Delay 13/FS 23/FS 4/FS 5/FS f > 0.5465fs 0.5465fs -50 dB f > 0.584fs +/- 0.03dB -6dB 0.584fs -50 0 0.5fs +/- 0.03 dB 0.4535fs dB +/- 0.03dB -6dB 0 0.5fs +/-0.03 dB 0.416fs -60 3.7 10.4 21.6 dB Hz -60 0 0.5fs +/- 0.05 dB 0.4535fs dB dB
ADC Filter Type 1 (USB mode, 272fs or Normal mode operation)
DAC Filter Type 1 (USB mode, 272fs or Normal mode operation)
Table 45 ADC/DAC Digital Filters Group Delay
TERMINOLOGY
1. 2. Stop Band Attenuation (dB) - the degree to which the frequency spectrum is attenuated (outside audio band) Pass-band Ripple - any variation of the frequency response in the pass-band region
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DAC FILTER RESPONSES
0.02
0
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0.01
-20
0
Response (dB)
-40
Response (dB)
0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.01 -0.02 -0.03 -0.04 -0.05
-60
-80
-100
-0.06 0 0.05 0.1 0.15 0.2 0.25 0.3 Frequency (Fs) 0.35 0.4 0.45 0.5
Figure 22 DAC Digital Filter Frequency Response - Type 0 Figure 23 DAC Digital Filter Ripple - Type 0
0.02
0
0.01
-20
0
Response (dB)
-40
Response (dB)
-0.01 -0.02 -0.03 -0.04
-60
-80
-0.05
-100 0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.06 0 0.05 0.1 0.15 0.2 0.25 0.3 Frequency (Fs) 0.35 0.4 0.45 0.5
Figure 24 DAC Digital Filter Frequency Response - Type 1 Figure 25 DAC Digital Filter Ripple - Type 1
0.02
0
0.01
-20
0
Response (dB)
-40
Response (dB)
-0.01 -0.02 -0.03 -0.04
-60
-80
-0.05
-100 0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.06 0 0.05 0.1 0.15 Frequency (Fs) 0.2 0.25
Figure 26 DAC Digital Filter Frequency Response - Type 2 Figure 27 DAC Digital Filter Ripple - Type 2
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0.25
0
WM8987L
0.2
-20
0.15 0.1
Response (dB)
Response (dB)
-40
0.05 0 -0.05 -0.1
-60
-80
-0.15 -0.2
-100 0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.25 0 0.05 0.1 0.15 Frequency (Fs) 0.2 0.25
Figure 28 DAC Digital Filter Frequency Response - Type 3 Figure 29 DAC Digital Filter Ripple - Type 3
ADC FILTER RESPONSES
0.04
0
0.03
-20
0.02
Response (dB)
Response (dB)
0.01 0 -0.01 -0.02
-40
-60
-80
-0.03
-100 0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.04 0 0.05 0.1 0.15 0.2 0.25 0.3 Frequency (Fs) 0.35 0.4 0.45 0.5
Figure 30 ADC Digital Filter Frequency Response - Type 0
0
Figure 31 ADC Digital Filter Ripple - Type 0
0.02 0.01
-20
0
Response (dB)
-40
Response (dB)
-0.01 -0.02 -0.03 -0.04
-60
-80
-0.05
-100 0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.06 0 0.05 0.1 0.15 0.2 0.25 0.3 Frequency (Fs) 0.35 0.4 0.45 0.5
Figure 32 ADC Digital Filter Frequency Response - Type 1
Figure 33 ADC Digital Filter Ripple - Type 1
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0.25
0
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0.2
-20
0.15 0.1
Response (dB)
Response (dB)
-40
0.05 0 -0.05 -0.1
-60
-80
-0.15 -0.2
-100 0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.25 0 0.05 0.1 0.15 Frequency (Fs) 0.2 0.25
Figure 34 ADC Digital Filter Frequency Response - Type 2
Figure 35 ADC Digital Filter Ripple - Type 2
0.25
0
0.2 0.15
-20
0.1
Response (dB)
Response (dB)
-40
0.05 0 -0.05 -0.1
-60
-80
-0.15 -0.2
-100 0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.25 0 0.05 0.1 0.15 Frequency (Fs) 0.2 0.25
Figure 36 ADC Digital Filter Frequency Response - Type 2
Figure 37 ADC Digital Filter Ripple - Type 3
DE-EMPHASIS FILTER RESPONSES
0
0.4 0.3
-2
0.2
Response (dB)
-4
Response (dB)
0.1 0 -0.1 -0.2
-6
-8
-0.3
-10 0 2000 4000 6000 8000 10000 Frequency (Fs) 12000 14000 16000
-0.4 0 2000 4000 6000 8000 10000 Frequency (Fs) 12000 14000 16000
Figure 38 De-emphasis Frequency Response (32kHz)
Figure 39 De-emphasis Error (32kHz)
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0
0.4 0.3
WM8987L
-2
0.2
Response (dB)
-4
Response (dB)
0.1 0 -0.1 -0.2
-6
-8
-0.3 -0.4
-10 0 5000 10000 Frequency (Fs) 15000 20000
0
5000
10000 Frequency (Fs)
15000
20000
Figure 40 De-emphasis Frequency Response (44.1kHz)
0
Figure 41 De-emphasis Error (44.1kHz)
0.4 0.3
-2
0.2
Response (dB)
-4
Response (dB)
0.1 0 -0.1 -0.2
-6
-8
-0.3 -0.4
-10 0 5000 10000 Frequency (Fs) 15000 20000
0
5000
10000 Frequency (Fs)
15000
20000
Figure 42 De-emphasis Frequency Response (48kHz)
Figure 43 De-emphasis Error (48kHz)
HIGHPASS FILTER
The WM8987L has a selectable digital highpass filter in the ADC filter path to remove DC offsets. The filter response is characterised by the following polynomial:
H(z) =
1 - z-1 1 - 0.9995z-1
0
Response (dB)
-5
-10
-15
0
0.0005
0.001 Frequency (Fs)
0.0015
0.002
Figure 44 ADC Highpass Filter Response
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WM8987L APPLICATIONS INFORMATION
RECOMMENDED EXTERNAL COMPONENTS
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Figure 45 Recommended External Components Diagram
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DRIVING BTL HEADSETS
To drive bridge-tied load (BTL) headsets, the analogue outputs should be used as follows: * * * ROUT1 is the non-inverting right output (HPR+) LOUT2 is the non-inverting left output (HPL+) ROUT2 is the inverting right output (HPR-)
* OUT3 is the inverting left output (HPL-) This setup is illustrated in Figure 46.
Figure 46 Driving a BTL headset It requires the following register settings: Set the ROUT1, LOUT2, ROUT2, MONO and OUT3 bits in R26 to `1' to enable the outputs and associated mixers. * Set LD2LO (R34), RD2RO (R37), LD2MO (R38) and OUT3SW (R24) to `1' to enable the correct audio paths (in the case of audio playback from an analogue source, select the input pin using LMIXSEL and RMIXSEL, and set LI2LO/LI2MO/RI2RO instead of LD2LO/LD2MO/RD2RO). * Set ROUT2INV = 1 in R24 to invert the right-channel signal going to ROUT2. * The left channel volume is controlled by LOUT2VOL and MONOVOL. To get the same RMS signal level at both pins, MONOVOL should be set 6dB higher than LOUT2VOL. * The right channel volume is controlled by ROUT1VOL and ROUT2VOL. Both should be set to the same value. To get the same gain as in the left channel, this value should be the same as LOUT2VOL. Note that this method for driving headsets can only be used where both ends of each transducer are electrically separate. It is incompatible with standard 2.5mm or 3.5mm headphone jacks, where a common ground serves as the return path for both left and right transducers. *
DRIVING SINGLE-ENDED HEADPHONES
USING CAPACITORS
To drive single-ended headphones using DC blocking capacitors, the analogue outputs should be used as follows: * * LOUT2 is the left output ROUT2 is the right output
* ROUT1 and OUT3 are unused and should be disabled This setup is illustrated in Figure 47.
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Figure 47 Driving single-ended headphones using DC-blocking capacitors It requires the following register settings: * * Set only the LOUT2 and ROUT2 bits in R26 to `1' to enable LOUT2, ROUT2 and the associated mixers. The ROUT1, MONO and OUT3 bits should remain at `0'. Set LD2LO (R34) and RD2RO (R37) to `1' to enable the correct audio paths (in the case of audio playback from an analogue source, select the input pin using LMIXSEL and RMIXSEL, and set LI2LO/RI2RO instead of LD2LO/RD2RO). Leave ROUT2INV = 0 in R24, so that the right-channel signal going to ROUT2 is not inverted. The left channel volume is controlled by LOUT2VOL.
* *
* The right channel volume is controlled by ROUT2VOL. This method for driving a headphone requires two capacitors in the LOUT2 and ROUT2 paths. Their capacitance C and the load resistance R together determine the lower cut-off frequency, fc. Increasing R or C lowers fc, improving the bass response. Smaller capacitance values will diminish the bass response. For example, assuming a 16 Ohm load and C = 220F: fc = 1 / 2 RLC1 = 1 / (2 x 16 x 220F) = 45 Hz
CAPLESS DRIVE
To drive single-ended headphones without DC blocking capacitors, the analogue outputs should be used as follows: * * LOUT2 is the left output ROUT2 is the right output
* OUT3 is a pseudo-ground output for the headphone * ROUT1 is unused and should be disabled This setup is illustrated in Figure 47.
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Figure 48 Driving single-ended headphones without DC-blocking capacitors It requires the following register settings: * * Set only the LOUT2, ROUT2 and OUT3 bits in R26 to `1' to enable LOUT2, ROUT2, OUT3 and the associated mixers. The ROUT1 and MONO bits should remain at `0'. Set LD2LO (R34) and RD2RO (R37) to `1' to enable the correct audio paths (in the case of audio playback from an analogue source, select the input pin using LMIXSEL and RMIXSEL, and set LI2LO/RI2RO instead of LD2LO/RD2RO). Leave OUT3SW = 0 in R24, so that the potential at OUT3 is the same as VREF. Leave ROUT2INV = 0 in R24, so that the right-channel signal going to ROUT2 is not inverted.
* *
* The left channel volume is controlled by LOUT2VOL. * The right channel volume is controlled by ROUT2VOL. As the OUT3 pin produces a DC voltage of AVDD/2 (=VREF), there is no DC offset between LOUT2/ROUT2 and OUT3, and therefore no DC blocking capacitors are required. This saves space and material cost in portable applications. However, compared to the single-ended configuration using capacitors, the WM8987L power consumption is higher, due to the additional power consumed in the OUT3 driver. It is recommended to connect the capless headphone outputs only to headphones, and not to the line input of another system. Although the built-in short circuit protection will prevent any damage to the headphone outputs, such a connection may be noisy, and may not function properly if the other system is grounded.
MICROPHONE INPUT CONFIGURATION
MICBIAS R1 680 Ohm to 2.2kOhm check microphone's specification LINPUT1/2 RINPUT1/2
FROM MICROPHONE
C2 1uF AGND R2 47kOhm C1 220pF
AGND
AGND
Figure 49 Recommended Circuit for Line Input
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WM8987L
Pre-Production For interfacing to a microphone, the ALC function should be enabled and the microphone boost switched on. Microphones held close to a speaker's mouth would normally use the 13dB gain setting, while tabletop or room microphones would need a 29dB boost. The recommended application circuit is shown above. R1 and R2 form part of the biasing network (refer to Microphone Bias section). R1 connected to MICBIAS is necessary only for electret type microphones that require a voltage bias. R2 should always be present to prevent the microphone input from charging to a high voltage which may damage the microphone on connection. R1 and R2 should be large so as not to attenuate the signal from the microphone, which can have source impedance greater than 2kOhm. C1 together with the source impedance of the microphone and the WM8987L input impedance forms an RF filter. C2 is a DC blocking capacitor to allow the microphone to be biased at a different DC voltage to the MICIN signal.
LINE INPUT CONFIGURATION
When LINPUT1/RINPUT1 or LINPUT2/RINPUT2 are used as line inputs, the microphone boost and ALC functions should normally be disabled. In order to avoid clipping, the user must ensure that the input signal does not exceed AVDD. This may require a potential divider circuit in some applications. It is also recommended to remove RF interference picked up on any cables using a simple first-order RC filter, as high-frequency components in the input signal may otherwise cause aliasing distortion in the audio band. AC signals with no DC bias should be fed to the WM8987L through a DC blocking capacitor, e.g. 1F.
MINIMISING POP NOISE AT THE ANALOGUE OUTPUTS
To minimise any pop or click noise when the system is powered up or down, the following procedures are recommended.
POWER UP
* Switch on power supplies. By default the WM8987L is in Standby Mode, the DAC is digitally muted and the Audio Interface and analogue outputs are all OFF (DACMU = 1 Power Management registers 1 and 2 are all zeros). Enable VMID and VREF. Enable DACs as required Enable line and / or headphone output buffers as required. Set DACMU = 0 to soft-un-mute the audio DACs.
* * * * * * *
POWER DOWN
Set DACMU = 1 to soft-mute the audio DACs. Disable all output buffers. Switch off the power supplies.
POWER MANAGEMENT EXAMPLES
OPERATION MODE
VMIDSEL
POWER MANAGEMENT (1) 0 DIGENB 1 PGAs
VREF AINR AINL
POWER MANAGEMENT (2) DACs
ROUT1 DACR DACL
ADCs
MICB ADCR ADCL
Output Buffers
ROUT2 LOUT2 MONO OUT3
Low-Power Standby BTL Headset Stereo Playback BTL Headset Phone Call Single-ended Headset Stereo Playback Single-ended Headset Phone Call Single-ended Headset Stereo Playback (capless) Single-ended Headset Phone Call (capless)
10 01 01 01 01 01 01
1 1 1 1 1 1 1
0 0 1 0 1 0 1
0 0 0 0 0 0 0
0 0 1 0 1 0 1
0 0 0 0 0 0 0
0 0 1 0 1 0 1
0 1 1 1 1 1 1
0 1 1 1 1 1 1
0 1 0 1 0 1 0
0 1 1 0 0 0 0
0 1 1 1 1 1 1
0 1 1 1 1 1 1
0 1 1 0 0 0 0
0 1 1 0 0 1 1
Table 46 Example Register Settings for Power Management
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PP Rev 3.0 January 2007 56
Pre-Production
WM8987L
PACKAGE DIMENSIONS
FL: 28 PIN COL QFN PLASTIC PACKAGE 4 X 4 X 0.75 mm BODY, 0.45 mm LEAD PITCH
DETAIL 1
D 22 28
DM043.F
21
1 4 INDEX AREA (D/2 X E/2) E
A
SEE DETAIL 2 15 14 e b 8 7 2X 1 bbb M C A B 2X aaa C aaa C
TOP VIEW
BOTTOM VIEW
ccc C A3 A 0.08 C 5
DETAIL 1
0.275MM
DETAIL 2
PIN 1 IDENTIFICATION 0.150MM SQUARE 0.275MM Datum
L 1 e L1 Terminal tip e/2
C
SEATING PLANE
SIDE VIEW
A1
DETAIL 2
W T A3 H b Exposed lead G
R
DETAIL 2
Symbols A A1 A3 b D E e G H L L1 T W aaa bbb ccc REF: MIN 0.725 0 0.18 3.95 3.95
Dimensions (mm) NOM MAX NOTE 0.75 0.775 0.02 0.05 0.203 REF 1 0.28 0.23 4.00 4.00 0.45 BSC 0.535 REF 0.100 REF 0.40 REF 0.05 REF 0.100 REF 0.230 REF 4.05 4.05
7
Tolerances of Form and Position 0.15 0.10 0.10 JEDEC, MO-220
NOTES: 1. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.15 mm AND 0.30 mm FROM TERMINAL TIP. 2. FALLS WITHIN JEDEC, MO-220, VARIATION VGGD-2. 3. ALL DIMENSIONS ARE IN MILLIMETRES. 4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JEDEC 95-1 SPP-002. 5. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS. 6. REFER TO APPLICATIONS NOTE WAN_0118 FOR FURTHER INFORMATION REGARDING PCB FOOTPRINTS AND QFN PACKAGE SOLDERING. 7. DEPENDING ON THE METHOD OF LEAD TERMINATION AT THE EDGE OF THE PACKAGE, PULL BACK (L1) MAY BE PRESENT. 8. THIS DRAWING IS SUBJECT TO CHANGE WITHOUT NOTICE.
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PP Rev 3.0 January 2007 57
WM8987L IMPORTANT NOTICE
Pre-Production
Wolfson Microelectronics plc ("Wolfson") products and services are sold subject to Wolfson's terms and conditions of sale, delivery and payment supplied at the time of order acknowledgement. Wolfson warrants performance of its products to the specifications in effect at the date of shipment. Wolfson reserves the right to make changes to its products and specifications or to discontinue any product or service without notice. Customers should therefore obtain the latest version of relevant information from Wolfson to verify that the information is current. Testing and other quality control techniques are utilised to the extent Wolfson deems necessary to support its warranty. Specific testing of all parameters of each device is not necessarily performed unless required by law or regulation. In order to minimise risks associated with customer applications, the customer must use adequate design and operating safeguards to minimise inherent or procedural hazards. Wolfson is not liable for applications assistance or customer product design. The customer is solely responsible for its selection and use of Wolfson products. Wolfson is not liable for such selection or use nor for use of any circuitry other than circuitry entirely embodied in a Wolfson product. Wolfson's products are not intended for use in life support systems, appliances, nuclear systems or systems where malfunction can reasonably be expected to result in personal injury, death or severe property or environmental damage. Any use of products by the customer for such purposes is at the customer's own risk. Wolfson does not grant any licence (express or implied) under any patent right, copyright, mask work right or other intellectual property right of Wolfson covering or relating to any combination, machine, or process in which its products or services might be or are used. Any provision or publication of any third party's products or services does not constitute Wolfson's approval, licence, warranty or endorsement thereof. Any third party trade marks contained in this document belong to the respective third party owner. Reproduction of information from Wolfson datasheets is permissible only if reproduction is without alteration and is accompanied by all associated copyright, proprietary and other notices (including this notice) and conditions. Wolfson is not liable for any unauthorised alteration of such information or for any reliance placed thereon. Any representations made, warranties given, and/or liabilities accepted by any person which differ from those contained in this datasheet or in Wolfson's standard terms and conditions of sale, delivery and payment are made, given and/or accepted at that person's own risk. Wolfson is not liable for any such representations, warranties or liabilities or for any reliance placed thereon by any person.
ADDRESS
Wolfson Microelectronics plc Westfield House 26 Westfield Road Edinburgh EH11 2QB United Kingdom Tel :: +44 (0)131 272 7000 Fax :: +44 (0)131 272 7001 Email :: sales@wolfsonmicro.com
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PP Rev 3.0 January 2007 58

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