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24-Bit, 625 kSPS, 109 dB - ADC with On-Chip Buffers, Serial Interface AD7763
FEATURES
120 dB dynamic range at 78 kHz output data rate 109 dB dynamic range at 625 kHz output data rate 112 dB SNR at 78 kHz output data rate 107 dB SNR at 625 kHz output data rate 625 kHz maximum fully filtered output word rate Programmable oversampling rate (32x to 256x) Flexible serial interface Fully differential modulator input On-chip differential amplifier for signal buffering Low-pass finite impulse response (FIR) filter with default or user-programmable coefficients Overrange alert bit Digital offset and gain correction registers Low power and power-down modes Synchronization of multiple devices via SYNC pin I2S interface mode
FUNCTIONAL BLOCK DIAGRAM
VIN- VIN+
DIFF
MULTIBIT - MODULATOR
AVDD1 AVDD2 AVDD3
VREF+ BUF REFGND RECONSTRUCTION
AVDD4 DECAPA DECAPB
AD7763
MCLK MCLKGND SYNC RESET SH2:0 ADR2:0 CDIV CONTROL LOGIC I/O OFFSET AND GAIN REGISTERS
PROGRAMMABLE DECIMATION
RBIAS AGND VDRIVE DVDD
FIR FILTER ENGINE
DGND
SDL DRDY SCO FSO
Figure 1.
APPLICATIONS
Data acquisition systems Vibration analysis Instrumentation
GENERAL DESCRIPTION
The AD7763 high performance, 24-bit, - analog-to-digital converter (ADC) combines wide input bandwidth and high speed with the benefits of - conversion, as well as performance of 107 dB SNR at 625 kSPS, making it ideal for high speed data acquisition. A wide dynamic range, combined with significantly reduced antialiasing requirements, simplifies the design process. An integrated buffer to drive the reference, a differential amplifier for signal buffering and level shifting, an overrange flag, internal gain and offset registers, and a low-pass, digital FIR filter make the AD7763 a compact, highly integrated data acquisition device requiring minimal peripheral component selection. In addition, the device offers programmable decimation rates and a digital FIR filter, which can be userprogrammed to ensure that its characteristics are tailored for the user's application. The AD7763 is ideal for applications demanding high SNR without necessitating the design of complex, frontend signal processing.
The differential input is sampled at up to 40 MSPS by an analog modulator. The modulator output is processed by a series of low-pass filters, the final filter having default or userprogrammable coefficients. The sample rate, filter corner frequencies, and output word rate are set by a combination of the external clock frequency and the configuration registers of the AD7763. The reference voltage supplied to the AD7763 determines the analog input range. With a 4 V reference, the analog input range is 3.2 V differential-biased around a common mode of 2 V. This common-mode biasing can be achieved using the on-chip differential amplifiers, further reducing the external signal conditioning requirements. The AD7763 is available in an exposed paddle, 64-lead TQFP_EP and is specified over the industrial temperature range from -40C to +85C. Table 1. Related Devices
Part No. AD7760 AD7762 Description 24-bit, 2.5 MSPS, 100 dB -, parallel interface 24-bit, 625 kSPS, 109 dB -, parallel interface
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c) 2005 Analog Devices, Inc. All rights reserved.
05476-001
SCP SCR
SDO
SDI FSI
I2S
AD7763 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Specifications..................................................................................... 3 Timing Specifications....................................................................... 5 Timing Diagrams.......................................................................... 6 Absolute Maximum Ratings............................................................ 7 ESD Caution.................................................................................. 7 Pin Configuration and Function Descriptions............................. 8 Terminology .................................................................................... 10 Typical Performance Characteristics ........................................... 11 Theory of Operation ...................................................................... 14 AD7763 Interface............................................................................ 15 Reading Data Using the SPI Interface ..................................... 15 Synchronization.......................................................................... 15 Sharing the Serial Bus ................................................................ 15 Writing to the AD7763 .............................................................. 16 Reading Status and Other Registers......................................... 17 Reading Data Using the I2S Interface....................................... 18 Clocking the AD7763..................................................................... 19 Example 1 .................................................................................... 19 Example 2 .................................................................................... 19 Driving the AD7763....................................................................... 20 Using the AD7763 ...................................................................... 21 Bias Resistor Selection ............................................................... 21 Decoupling and Layout Recommendations................................ 22 Supply Decoupling ..................................................................... 23 Additional Decoupling .............................................................. 23 Reference Voltage Filtering ....................................................... 23 Differential Amplifier Components ........................................ 23 Exposed Paddle........................................................................... 23 Layout Considerations............................................................... 23 Programmable FIR Filter............................................................... 24 Downloading a User-Defined Filter ............................................ 25 Example Filter Download ......................................................... 26 Registers........................................................................................... 27 Control Register 1--Address 0x001......................................... 27 Control Register 2--Address 0x002......................................... 27 Status Register (Read Only) ...................................................... 28 Offset Register--Address 0x003............................................... 28 Gain Register--Address 0x004 ................................................. 28 Overrange Register--Address 0x005....................................... 28 Outline Dimensions ....................................................................... 29 Ordering Guide .......................................................................... 29
REVISION HISTORY
10/05--Revision 0: Initial Version
Rev. 0 | Page 2 of 32
AD7763 SPECIFICATIONS
AVDD1 = DVDD = VDRIVE = 2.5 V; AVDD2 = AVDD3 = AVDD4 = 5 V; VREF = 4.096 V; MCLK amplitude = 5 V; TA = 25C; normal mode, using on-chip amplifier with components as shown in Table 10, unless otherwise noted. 1 Table 2.
Parameter DYNAMIC PERFORMANCE Decimate x 256 Dynamic Range Signal-to-Noise Ratio (SNR) 2 Spurious-Free Dynamic Range (SFDR) Total Harmonic Distortion (THD) Test Conditions/Comments MCLK = 40 MHz, ODR = 78 kHz, FIN = 1 kHz Modulator inputs shorted Input amplitude = -0.5 dBFS Input amplitude = -60 dB Nonharmonic, input amplitude = -6 dB Input amplitude = -60 dB Input amplitude = -0.5 dBFS Input amplitude = -6 dB Input amplitude = -60 dB MCLK = 40 MHz, ODR = 312.5 kHz, FIN = 1 kHz Modulator inputs shorted Input amplitude = -0.5 dBFS Nonharmonic, input amplitude = -6 dB MCLK = 40 MHz, ODR = 625 kHz, FIN = 100 kHz Modulator inputs shorted Input amplitude = -0.5 dBFS Nonharmonic, input amplitude = -6 dB Input amplitude = -0.5 dBFS Input amplitude = -6 dB Specification Unit
119 120.5 112 59 126 77 -105 -106 -75 112 113 109.5 126 108 109.5 107 120 -105 -107 24
dB min dB typ dB typ dBc typ dBc typ dBc typ dB typ dBc typ dBc typ dB min dB typ dB typ dBc typ dB min dB typ dB typ dBc typ dB typ dBc typ Bits % typ % typ % max % typ %FS/C typ %FS/C typ
Decimate x 64 Dynamic Range Signal-to-Noise Ratio (SNR)2 Spurious-Free Dynamic Range (SFDR) Decimate x 32 Dynamic Range Signal-to-Noise Ratio (SNR)2 Spurious-Free Dynamic Range (SFDR) Total Harmonic Distortion (THD) DC ACCURACY Resolution Differential Nonlinearity Integral Nonlinearity Zero Error Gain Error Zero Error Drift Gain Error Drift DIGITAL FILTER RESPONSE Decimate x 32 Group Delay Decimate x 64 Group Delay Decimate x 256 Group Delay ANALOG INPUT Differential Input Voltage Input Capacitance
Guaranteed monotonic to 24 bits 0.00076 0.014 0.02 0.018 10 0.0002
MCLK = 40 MHz MCLK = 40 MHz MCLK = 40 MHz VIN(+) - VIN(-), VREF = 2.5 V VIN(+) - Vin(-), VREF = 4.096 V At internal buffer inputs At modulator inputs
47 91.5 358 2 3.25 5 55
s typ s typ s typ V p-p V p-p pF typ pF typ
Rev. 0 | Page 3 of 32
AD7763
Parameter REFERENCE INPUT VREF Input Voltage VREF Input DC Leakage Current VREF Input Capacitance POWER DISSIPATION Total Power Dissipation Standby Mode POWER REQUIREMENTS AVDD1 (Modulator Supply) AVDD2 (General Supply) AVDD3 (Differential Amplifier Supply) AVDD4 (Reference Buffer Supply) DVDD VDRIVE Normal Mode AIDD1 (Modulator) AIDD2 (General) AIDD4 (Reference Buffer) Low Power Mode AIDD1 (Modulator) AIDD2 (General) AIDD4 (Reference Buffer) AIDD3 (Diff Amp) DIDD DIGITAL I/O MCLK Input Amplitude 3 Input Capacitance Input Leakage Current Three-State Leakage Current (SDO) VINH VINL VOH 4 VOL
1 2 3
Test Conditions/Comments VDD3 = 3.3 V 5% VDD3 = 5 V 5%
Specification +2.5 +4.096 1 5 955.5 651 6.35 +2.5 +5 +3.15/+5.25 +3.15/+5.25 +2.5 +1.65/+2.7 49/52 40/43 35/37 26/28 20/23 10/11 41/45 56/62 5 7.3 1 1 0.7 x VDRIVE 0.3 x VDRIVE 1.5 0.1
Unit V max V max A max pF max mW max mW max mW typ V V V min/max V min/max V V min/max mA typ/max mA typ/max mA typ/max mA typ/max mA typ/max mA typ/max mA typ/max mA typ/max V typ pF typ A/pin max A max V min V max V min V max
Normal power mode Low power mode Clock stopped 5% 5%
5%
AVDD4 = 5 V
AVDD4 = 5 V AVDD3 = 5 V, both modes Both modes
See the Terminology section. SNR specifications in dB are referred to a full-scale input, FS, and tested with an input signal at 0.5 dB below full scale, unless otherwise specified. While the AD7763 can function with an MCLK amplitude of less than 5 V, this is the recommended amplitude to achieve the performance as stated. 4 Tested with a 400 A load current.
Rev. 0 | Page 4 of 32
AD7763 TIMING SPECIFICATIONS
AVDD1 = DVDD = VDRIVE = 2.5 V, AVDD2 = AVDD3 = AVDD4 = 5 V, TA = 25C, normal mode, unless otherwise noted. Table 3.
Parameter fMCLK fICLK t1 1 t21 t3 t3A 4 t3B4 t4 5 t4A4, 5 t4B4, 5 t5 t64 t7 t8 t9 t10 t11 t12 t13 t14 t15
1 2
Limit at TMIN, TMAX 1 40 500 20 1 x tICLK or 0.5 x tICLK 2 1 x tICLK or 0.5 x tICLK2 tSCO 3 2 3 32 x tSCO3 1 2 6.5 5 0.5 x tSCO3 16 x tSCO3 tSCO3 5.5 1 x tSCO3 12 10 12 16 x tSCO3
Unit MHz min MHz max kHz min MHz max typ typ typ ns typ ns typ typ ns typ ns typ ns max ns max ns min typ typ ns max min ns min ns min ns min typ
Description Applied master clock frequency Internal modulator clock derived from MCLK SCO high period SCO low period DRDY low period SCO rising edge to DRDY falling edge SCO rising edge to DRDY rising edge FSO low period SCO rising edge to FSO falling edge SCO falling edge to FSO rising edge Initial data access time SCO rising edge to SDO valid SDO valid after SCO falling edge DRDY rising edge to SDL falling edge SDL pulse width SDO three-state to SCO rising edge FSI low period SDI setup time SDI hold time FSI setup time SDL falling edge to SDL falling edge
tICLK = 1/fICLK. SCO frequency selected by SCR and CDIV pins. 3 tSCO = t1 + t2. 4 All edges mentioned refer to SCP = 0. Invert SCO edges for SCP = 1. 5 In decimate x 32 mode, this time specification applies only when CDIV = 0 and SCR =1. For all other combinations of CDIV and SCR in decimate x 32 mode, the FSO signal is constantly logic low.
Rev. 0 | Page 5 of 32
AD7763
TIMING DIAGRAMS
t4
FSO (O)
t4A t1
t4B
SCO (O)
t3B t3A
DRDY (O)
t2
t3
SDO (O)
t5
t6
t7
D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
t10
ST6 ST5 ST4 ST3 ST2 ST1 ST0
D23 D22 D21 D20 D19 D18 D17 D16 D15 D14 D13 D12 D11 D10
t8
SDL (O)
t9 t15
05476-002
Figure 2. SPI(R) Interface Serial Read Timing Diagram
32 x tSCO
SCO (O)
t14
FSI (I)
t1
t2
t11
SDI (I) ALL ADR2 ADR1 ADR0
t12
RA11 RA10
t13
RA1 RA0 D15 D14 D1 D0
05476-003
Figure 3. Register Write
32 x tSCO
SCO (O)
32 x tSCO
32 x tSCO
32 x tSCO
DRDY A (O)
SDO (O)
SERIAL DATA FROM ADC A
SERIAL DATA FROM ADC B
SERIAL DATA FROM ADC C
SERIAL DATA FROM ADC D
FSO A
FSO B
FSO C
FSO D
05476-004
Figure 4. SPI Interface Serial Read Timing with Multiple AD7763 Devices Sharing the Serial Bus
Rev. 0 | Page 6 of 32
AD7763 ABSOLUTE MAXIMUM RATINGS
TA = 25C, unless otherwise noted. Table 4.
Parameter AVDD1 to GND (AVDD2, AVDD3, AVDD4) to GND DVDD to GND VDRIVE to GND VIN+, VIN- to GND Digital Input Voltage to GND1 MCLK to MCLKGND VREF to GND2 AGND to DGND Input Current to Any Pin Except Supplies3 Operating Temperature Range Commercial Storage Temperature Range Junction Temperature TQFP_EP Exposed Paddle JA Thermal Impedance JC Thermal Impedance Lead Temperature, Soldering Vapor Phase (60 sec) Infrared (15 sec) ESD
1
Rating -0.3 V to +3 V -0.3 V to +6 V -0.3 V to +3 V -0.3 V to +3 V -0.3 V to +6 V -0.3 V to DVDD + 0.3 V -0.3 V to +6 V -0.3 V to AVDD4 + 0.3 V -0.3 V to +0.3 V 10 mA -40C to +85C -65C to +150C 150C 92.7C/W 5.1C/W 215C 220C 600 V
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Absolute maximum voltage on digital inputs is 3.0 V or DVDD + 0.3 V, whichever is lower. 2 Absolute maximum voltage on VREF input is 6.0 V or AVDD4 + 0.3 V, whichever is lower. 3 Transient currents of up to 200 mA do not cause SCR latch-up.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev. 0 | Page 7 of 32
AD7763 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
VDRIVE DGND DGND DGND DGND DGND CDIV SCO SDO SCR FSO
64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 ADR0 PIN 1 47 ADR1 46 ADR2 45 SH0 44 VDRIVE
DGND 1 MCLKGND AVDD2 AGND2 AVDD1 AGND1
2
MCLK 3
4 5 6 7
SCP
43 DGND 42 DGND 41 DVDD 40 SH1 39 SH2 38 DRDY 37 RESET 36 SYNC 35 DGND 34 AGND1 33 AVDD1
AD7763
TOP VIEW (Not to Scale)
DECAPA 8 REFGND 9 VREF+ 10 AGND4 11 AVDD4 12 AGND2 13 AVDD2 14 AVDD2 15 AGND2 16
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
VINA-
VOUTA-
RBIAS
VINA+
VOUTA+
AGND2
AGND3
VIN+
VIN-
AGND2
AGND3
AGND3
SDL
SDI
FSI
I2S
DECAPB
AGND3
AVDD3
AVDD2
Figure 5. Pin Configuration
Table 5. Pin Function Descriptions
Pin No. 6, 33 4, 14, 15, 27 24 12 7, 34 5, 13, 16, 18, 28 23, 29, 31, 32 11 9 41 44, 63 Mnemonic AVDD1 AVDD2 AVDD3 AVDD4 AGND1 AGND2 AGND3 AGND4 REFGND DVDD VDRIVE Description Power Supply for Modulator, 2.5 V. These pins should be decoupled to AGND1 with 100 nF and 10 F capacitors on each pin. Power Supply, 5 V. These pins should be decoupled to AGND2 with 100 nF capacitors on each of Pin 4, Pin 14, and Pin 15. Pin 27 should be connected to Pin 14 via an 8.2 nH inductor. Power Supply for Differential Amplifier, 3.3 V to 5 V. This pin should be decoupled to AGND3 with a 100 nF capacitor. Power Supply for Reference Buffer, 3.3 V to 5 V. This pin should be decoupled to AGND4 with a 10 nF capacitor in series with a 10 resistor. Power Supply Ground for Analog Circuitry Powered by AVDD1. Power Supply Ground for Analog Circuitry Powered by AVDD2. Power Supply Ground for Analog Circuitry Powered by AVDD3. Power Supply Ground for Analog Circuitry Powered by AVDD4. Reference Ground. Ground connection for the reference voltage. Power Supply for Digital Circuitry and FIR Filter, 2.5 V. This pin should be decoupled to DGND with a 100 nF capacitor. Logic Power Supply Input, 1.8 V to 2.5 V. The voltage supplied at these pins determines the operating voltage of the logic interface. These pins must be connected together and tied to the same supply. Each pin should also be decoupled to DGND with a 100 nF capacitor. Ground Reference for Digital Circuitry. Positive Input to Differential Amplifier. Negative Input to Differential Amplifier. Negative Output from Differential Amplifier. Positive Output from Differential Amplifier. Positive Input to the Modulator. Negative Input to the Modulator. Reference Input. The input range of this pin is determined by the reference buffer supply voltage (AVDD4). See the Reference Voltage Filtering section for more details. Decoupling Pin. A 100 nF capacitor must be inserted between this pin and AGND1. Decoupling Pin. A 33 pF capacitor must be inserted between this pin and AGND3.
Rev. 0 | Page 8 of 32
1, 35, 42, 43, 53, 57, 59, 62, 64 19 20 21 22 25 26 10 8 30
DGND VINA+ VINA- VOUTA- VOUTA+ VIN+ VIN- VREF+ DECAPA DECAPB
05476-005
AD7763
Pin No. 17 37 3 2 36 38 39, 40, 45 Mnemonic RBIAS RESET MCLK MCLKGND SYNC DRDY SH2:0 Description Bias Current Setting. A resistor must be inserted between this pin and AGND. See the Bias Resistor Selection section. A falling edge on this pin resets all internal digital circuitry. Holding this pin low keeps the AD7763 in a reset state. Master Clock Input. A low jitter digital clock must be applied to this pin. The output data rate depends on the frequency of this clock. See the Clocking the AD7763 section. Master Clock Ground Sensing Pin. Synchronization Input. A falling edge on this pin resets the internal filter. This can be used to synchronize multiple devices in a system. Data Ready Output. Each time new conversion data is available, an active low pulse, 1/2 ICLK period wide, is produced on this pin. See the AD7763 Interface section. Share Pins 2:0. For multiple AD7763 devices sharing a common serial bus. Each device is wired with the binary value that represents the number of devices sharing the serial bus. SH2 is the MSB. See the Sharing the Serial Bus section. Address 2:0. Allows multiple AD7763 devices to share a common serial bus. Each device must be programmed with an individual address using these three pins. See the Sharing the Serial Bus section. Serial Clock Polarity. Determines on which edge of SCO the data bits are clocked out and on which edge they are valid. All timing diagrams are shown with SCP = 0, and all SCO edges shown should be inverted for SCP = 1. Serial Data Latch. A pulse is output on this pin after every 16 data bits. The pulse is one SCO period wide and can be used in conjunction with FSO as an alternative framing method for serial transfers requiring a framing signal more frequent than every 32 bits. Frame Sync In. The status of this pin is checked on the falling edge of SCO. If this pin is low, then the first data bit is latched in on the next SCO falling edge when SCP = 0 or on the rising edge of SCO if SCP = 1. Serial Data In. The first data bit (MSB) must be valid on the next SCO falling edge when SCP = 0 (or SCO rising edge SCP = 1) after the FSI event has been latched. Each write requires 32 bits: the ALL bit, 3 address bits, and 12 register address bits, followed by the remaining 16 bits of data to be written to the device. Serial Data Out. Address, status, and data bits are clocked out on this line during each serial transfer. If SCP = 0, each bit is clocked out on an SCO rising edge and is valid on the falling edge. When the I2S pin is set to logic high, this pin outputs the signal defined as SD in the I2S bus specification. See the Reading Data Using the I2S Interface section for details. Serial Clock Out. This clock signal is derived from the internal ICLK signal. The frequency of SCO is equal to either ICLK or ICLK/2, depending on the state of the CDIV and SCR pins (see the AD7763 Interface section). When the I2S pin is logic high, this pin outputs the signal defined as SCK by the I2S bus specification. See the Reading Data Using the I2S Interface section. Frame Sync Out. This signal frames the serial data output and is 32 SCO periods wide. The exception to the framing behavior of FSO occurs in decimate x 32 mode, where, for certain combinations of CDIV and SCR, the FSO signal is constantly logic low. See the Reading Data Using the SPI Interface section. When the I2S pin is set to logic high, this pin outputs the signal defined as WS in the I2S bus specification. See the Reading Data Using the I2S Interface section. Clock Divider. This pin is used to select the ratio of MCLK to ICLK. See the AD7763 Interface section. Serial Clock Rate. This pin and the CDIV pin program the SCO frequency (see Table 7). I2S Select. A Logic 1 on this pin changes the serial data-out mode from SPI to I2S. The SDO pin outputs as the SD signal, the SCO pin outputs the SCK signal, and the FSO pin outputs the WS signal. When writing to the AD7763, the I2S pin is set to logic low and the SPI interface is used. See the Reading Data Using the I2S Interface section for further details.
46 to 48
ADR2:0
49
SCP
50
SDL
51
FSI
52
SDI
54
SDO
55
SCO
56
FSO
58 60 61
CDIV SCR I2S
Rev. 0 | Page 9 of 32
AD7763 TERMINOLOGY
Signal-to-Noise Ratio (SNR) The ratio of the rms value of the actual input signal to the rms sum of all other spectral components below the Nyquist frequency, excluding harmonics and dc. The value for SNR is expressed in decibels. Total Harmonic Distortion (THD) The ratio of the rms sum of harmonics to the fundamental. For the AD7763, it is defined as Integral Nonlinearity (INL) The maximum deviation from a straight line passing through the endpoints of the ADC transfer function. Differential Nonlinearity (DNL) The difference between the measured and the ideal 1 LSB change between any two adjacent codes in the ADC. Zero Error The difference between the ideal midscale input voltage (0 V) and the actual voltage producing the midscale output code. Zero Error Drift The change in the actual zero error value due to a temperature change of 1C. It is expressed as a percentage of full scale at room temperature. Gain Error The first transition (from 100...000 to 100...001) should occur for an analog voltage 1/2 LSB above the nominal negative full scale. The last transition (from 011...110 to 011...111) should occur for an analog voltage 1 1/2 LSB below the nominal full scale. The gain error is the deviation of the difference between the actual level of the last transition and the actual level of the first transition, from the difference between the ideal levels. Gain Error Drift The change in the actual gain error value due to a temperature change of 1C. It is expressed as a percentage of full scale at room temperature.
THD (dB ) = 20 log where:
V22 + V32 + V42 + V52 + V62 V1
V1 is the rms amplitude of the fundamental. V2, V3, V4, V5, and V6 are the rms amplitudes of the second to the sixth harmonic. Nonharmonic Spurious-Free Dynamic Range (SFDR) The ratio of the rms signal amplitude to the rms value of the peak spurious spectral component, excluding harmonics. Dynamic Range The ratio of the rms value of the full scale to the rms noise measured with the inputs shorted together. The value for dynamic range is expressed in decibels.
Rev. 0 | Page 10 of 32
AD7763 TYPICAL PERFORMANCE CHARACTERISTICS
AVDD1 = DVDD = VDRIVE = 2.5 V, AVDD2 = AVDD3 = AVDD4 = 5 V, VREF = 4.096 V, TA = 25C, normal mode, unless otherwise noted. All FFTs are generated from 65536 samples using a 7-term Blackman-Harris window.
0
0
-50
-50
-100
AMPLITUDE (dB)
AMPLITUDE (dB)
-100
-150
-150
-200
05476-007
-200
05476-006
-250
0
5000
10000
15000
20000
25000
30000
35000
-250
0
5000
10000
15000
20000
25000
30000
35000
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 6. Normal Mode FFT, 1 kHz, -0.5 dB Input Tone, 256x Decimation
0
Figure 9. Low Power FFT, 1 kHz, -0.5 dB Input Tone, 256x Decimation
0
-50
-50
AMPLITUDE (dB)
-100
AMPLITUDE (dB)
05476-011
-100
-150
-150
-200
-200
05476-010
-250
0
5000
10000
15000
20000
25000
30000
35000
-250
0
5000
10000
15000
20000
25000
30000
35000
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 7. Normal Mode FFT, 1 kHz, -0.6 dB Input Tone, 256x Decimation
0
Figure 10. Low Power FFT, 1 kHz, -6 dB Input Tone, 256x Decimation
0
-50
-50
AMPLITUDE (dB)
-100
AMPLITUDE (dB)
05476-032
-100
-150
-150
-200
-200
05476-031
-250
0
5000
10000
15000
20000
25000
30000
35000
-250
0
5000
10000
15000
20000
25000
30000
35000
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 8. Normal Mode FFT, 1 kHz, -60 dB Input Tone, 256x Decimation
Figure 11. Low Power FFT, 1 kHz, -60 dB Input Tone, 256x Decimation
Rev. 0 | Page 11 of 32
AD7763
0 0
-50
-50
AMPLITUDE (dB)
-100
AMPLITUDE (dB)
05476-009
-100
-150
-150
-200
-200
05476-008
-250
0
50000
100000
150000
200000
250000
300000
-250
0
50000
100000
150000
200000
250000
300000
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 12. Normal Mode FFT, 100 kHz, -0.5 dB Input Tone, 32x Decimation
0
Figure 15. Low Power FFT, 100 kHz, -0.5 dB Input Tone, 32x Decimation
0
-50
-50
AMPLITUDE (dB)
-100
AMPLITUDE (dB)
05476-030
-100
-150
-150
-200
-200
05476-029
-250
0
50000
100000
150000
200000
250000
300000
-250
0
50000
100000
150000
200000
250000
300000
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 13. Normal Mode FFT, 100 kHz, -6 dB Input Tone, 32x Decimation
120 -60dB 118 116 -6dB
Figure 16. Low Power FFT, 100 kHz, -6 dB Input Tone, 32x Decimation
116 -60dB 114 -6dB 112
SNR (dBFS)
SNR (dBFS)
114
-0.5dB 110
112 -0.5dB 110
108
05476-036
106
0
64
128 DECIMATION RATE (x)
192
256
104
0
64
128 DECIMATION RATE (x)
192
256
Figure 14. Normal Mode SNR vs. Decimation Rate, 1 kHz Input Tone
Figure 17. Low Power SNR vs. Decimation Rate, 1 kHz Input Tone
Rev. 0 | Page 12 of 32
05476-033
108
106
AD7763
4500 4000
5000 6000
3500 3000
4000
OCCURENCE
2500 2000 1500 1000
OCCURENCE
05476-035
3000
2000
1000
500 0 8385341 8385351 8385361 8385371 8385381 8385391 8385401 24-BIT CODE
0 8383091
8383111
8383131
8383151
8383171
8383191
24-BIT CODE
Figure 18. Normal Mode, 24-Bit Histogram, 256x Decimation
0.0010
Figure 21. Low Power 24-Bit Histogram, 256x Decimation
0.0015 +85C
+85C 0.0005
0.0010
INL (%)
INL (%)
+25C 0 -40C
0.0005 +25C
0 -40C -0.0005
05476-037
-0.0005
-0.0010 0 4194304 8388608 24-BIT CODE 12582912
-0.0010 0 4194304 8388608 24-BIT CODE 12582912
16777216
16777216
Figure 19. 24-Bit INL, Normal Power Mode
0.65
Figure 22. 24-Bit INL, Low Power Mode
0.4
0.2
DNL (LSB)
0
-0.2
-0.4
05476-039
-0.6 0 4194304 8388608 24-BIT CODE 12582912
16777216
Figure 20. 24-Bit DNL
Rev. 0 | Page 13 of 32
05476-038
05476-034
AD7763 THEORY OF OPERATION
The AD7763 employs a - conversion technique to convert the analog input into an equivalent digital word. The modulator samples the input waveform and outputs an equivalent digital word to the digital filter at a rate equal to ICLK. Due to the high oversampling rate, which spreads the quantization noise from 0 to fICLK, the noise energy contained in the band of interest is reduced (see Figure 23). To further reduce quantization noise, a high order modulator is employed to shape the noise spectrum; thus, most of the noise energy is shifted out of the band of interest (see Figure 24). The digital filtering that follows the modulator removes the large out-of-band quantization noise (see Figure 25), while also reducing the data rate from fICLK at the input of the filter to fICLK/32 or less at the output of the filter, depending on the decimation rate used. Digital filtering has certain advantages over analog filtering. It does not introduce significant noise or distortion and can be made perfectly linear phase. The AD7763 employs three finite impulse response (FIR) filters in series. By using different combinations of decimation ratios and filter selection, data can be obtained from the AD7763 at four different data rates. The first filter receives data from the modulator at ICLK MHz, where it is decimated x 4 to output data at (ICLK/4) MHz. The second filter allows the decimation rate to be chosen from 8x to 32x. The third filter has a fixed decimation rate of 2x, is user programmable, and has a default configuration (see the Programmable FIR Filter section). This filter can be bypassed. Table 6 shows some characteristics of the default filter. The group delay of the filter is defined as the delay to the center of the impulse response and is equal to the computation plus filter delays. The delay until valid data is available (the DVALID status bit is set) is equal to 2x the filter delay plus the computation delay.
QUANTIZATION NOISE fICLK/2
05476-024 05476-012 05476-025
BAND OF INTEREST
Figure 23. - ADC, Quantization Noise
NOISE SHAPING
BAND OF INTEREST
fICLK/2
Figure 24. - ADC, Noise Shaping
DIGITAL FILTER CUTOFF FREQUENCY
BAND OF INTEREST
fICLK/2
Figure 25. - ADC, Digital Filter Cutoff Frequency
Table 6. Configuration With Default Filter
ICLK Frequency 20 MHz 20 MHz 20 MHz 20 MHz 20 MHz 20 MHz 20 MHz 12.288 MHz 12.288 MHz 12.288 MHz 12.288 MHz Filter 1 4x 4x 4x 4x 4x 4x 4x 4x 4x 4x 4x Filter 2 4x 8x 8x 16x 16x 32x 32x 8x 16x 32x 32x Filter 3 2x Bypassed 2x Bypassed 2x Bypassed 2x 2x 2x Bypassed 2x Data State Fully filtered Partially filtered Fully filtered Partially filtered Fully filtered Partially filtered Fully filtered Fully filtered Fully filtered Partially filtered Fully filtered Computation Delay 1.775 s 2.6 s 2.25 s 4.175 s 3.1 s 7.325 s 4.65 s 3.66 s 5.05 s 11.92 s 7.57 s Filter Delay 44.4 s 10.8 s 87.6 s 20.4 s 174 s 39.6 s 346.8 s 142.6 s 283.2 s 64.45 s 564.5 s Pass Band Bandwidth 250 kHz 140.625 kHz 125 kHz 70.3125 kHz 62.5 kHz 35.156 kHz 31.25 kHz 76.8 kHz 38.4 kHz 21.6 kHz 19.2 kHz Output Data Rate (ODR) 625 kHz 625 kHz 312.5 kHz 312.5 kHz 156.25 kHz 156.25 kHz 78.125 kHz 192 kHz 96 kHz 96 kHz 48 kHz
Rev. 0 | Page 14 of 32
AD7763 AD7763 INTERFACE
READING DATA USING THE SPI INTERFACE
The timing diagram in Figure 2 shows how the AD7763 transmits its conversion results using the SPI-compatible serial interface. The data being read from the AD7763 is clocked out using the serial clock output, SCO. The SCO frequency is dependent on the state of the serial clock output rate pin, SCR, and the clock divider mode chosen by the state of the clock divider pin, CDIV (see the Clocking the AD7763 section). Table 7 shows both the SCO frequency and the ICLK frequency for the AD7763, resulting from the states of both the CDIV and SCR pins.
Table 7. SCO Frequency
Clock Divide Mode Divide by 1 Divide by 2
1
The AD7763 also features a serial data latch output, SDL, which outputs a pulse every 16 data bits. The SDL output offers an alternative framing signal for serial transfers, which require a framing signal more frequent than every 32 bits.
SYNCHRONIZATION
The SYNC input to the AD7763 provides a synchronization function that allows the user to begin gathering samples of the analog front-end input from a known point in time. The SYNC function allows multiple AD7763s, operated from the same master clock and using the same SYNC signal, to be synchronized so that each ADC simultaneously updates its output register. Using a common SYNC signal to all AD7763 devices in a system allows synchronization to occur. On the falling edge of the SYNC signal, the digital filter sequencer is reset to 0. The filter is held in reset state until a rising edge of the SCO senses SYNC high. Thus, to perform a synchronization of devices, a SYNC pulse of a minimum of 2.5 ICLK cycles in length can be applied, synchronous to the falling edge of SCO. On the first rising edge of SCO after SYNC goes logic high, the filter is taken out of reset, and the multiple parts gather input samples synchronously. Following a SYNC, the digital filter needs time to settle before valid data can be read from the AD7763. The user knows there is valid data on the SDO line by checking the DVALID status bit (see D3 in the status bits listing) that is output with each conversion result. The time from the rising edge of SYNC until the DVALID bit is asserted is dependent on the filter configuration used. See the Theory of Operation section and the figures listed in Table 6 for details on calculating the time until DVALID is asserted.
CDIV 1 0
SCR 0 1 0 1
SCO Frequency MCLK MCLK MCLK/2 MCLK1
ICLK Frequency MCLK MCLK MCLK/2 MCLK/2
In decimate x 32 mode, when CDIV = 0 and SCR = 1, FSO pulses low for 32 SCO clock cycles, as shown in Figure 2. For all other combinations of CDIV and SCR in decimate x 32 mode, FSO is continuously low.
An active low pulse of one SCO period on the data-ready output, DRDY, indicates a new conversion result is available at the AD7763 serial data output, SDO. Each bit of the new conversion result is clocked onto the SDO line on the rising SCO edge and is valid on the falling SCO edge (for SCP = 0). The conversion result spans 32 SCO clock cycles and consists of 24 data bits in twos complement form, followed by 7 status bits.
D6 ADR2 D5 ADR1 D4 ADR0 D3 DVALID D2 OVR D1 LPWR D0 FILTER_OK
The conversion result output on the SDO line is framed by the frame synchronization output, FSO, which is sent logic low for 32 SCO cycles following the rising edge of the DRDY signal. Note that the SDO line is in three-state for one clock cycle before the FSO signal returns to logic high, which means that only 31 actual data bits are output in each conversion. The first three status bits, ADR[2:0], are the device address bits. The DVALID bit is asserted when the data being clocked out on the SDO line is valid. Table 19 contains descriptions of the other status bits: OVR, LPWR, and FILTER_OK. There is an exception to the behavior of FSO when the AD7763 operates in decimate x 32 mode (see Endnote 1 of Table 7). If SCR and CDIV are chosen so that the SCO frequency output has the capability to clock through only 32 SCO cycles before the MSB of the next conversion result is output, then FSO stays logic low continuously.
SHARING THE SERIAL BUS
The AD7763 functionality allows up to eight devices to share the same serial bus, SDO, depending on the decimation rate that is chosen. Table 8 details the maximum number of devices that can share the same SDO line for each decimation rate (x32, x64, x128, x256).
Table 8. Maximum Number of Devices Sharing SDO
Decimation Rate SCO (MHz) 40 20 x32 2 N/A x64 4 2 x128 8 4 x256 8 8
Maximum Number of Devices Sharing SDO
The Share Pins SH[2:0] of all the devices sharing the serial bus must be programmed with the number of devices that are sharing the serial bus.
Rev. 0 | Page 15 of 32
AD7763
Using the Address Pins ADR[2:0], all devices that share the serial bus are assigned binary addresses from 000 to 111 (depending on the number of devices in the share scheme). The address assigned to each device must not have a value greater than the number of devices sharing the serial bus. Thus, ADR[2:0] SH[2:0]. This applies to all the devices that share the serial bus. Note also that each of the devices in the share scheme must have a different individual address. For the device in the share scheme with an address of 000, the SDO line comes out of three-state on the first rising edge of SCO after the DRDY pulse and returns to three-state 5.5 ns before the 31st SCO rising edge. For the next device sharing the serial bus, Address 001, the SDO line comes out of three-state on the 33rd SCO rising edge (that is, the first SCO rising edge of the next conversion output cycle). Thus, the SDO line goes into tristate for one SCO cycle in between data being clocked onto SDO by two different devices that share the SDO line. This means that a bus contention issue is avoided. This pattern of behavior continues for the rest of the devices sharing the serial bus. Each AD7763 device sharing the serial bus outputs its own FSO signal. Figure 26 shows an example of four devices sharing the same serial bus. All the devices in the share chain shown in Figure 26 operate in decimate x 64 mode (selected by writing to Control Register 1--Address 0x001) and use a maximum SCO signal of 40 MHz (see the Clocking the AD7763 section). The Share Pins SH[2:0] of all the devices shown in Figure 26 are set to 011, corresponding to the four devices that are in the share configuration. Each AD7763 is hardwired with a different binary address ranging from 000 to 011, using the Address Pins ADR[2:0]. The timing diagram for the share configuration shown in Figure 26 is detailed in Figure 4. Device A outputs its 32-bit conversion result on the SDO line during the first 32 SCO cycles (as per the format shown in the Reading Data Using the SPI Interfacesection). Device B then outputs its conversion result during the next 32 SCO cycles, and so on for Device C and Device D. Note the way in which the SDO line is threestated, separating data from each of the devices sharing the serial bus. The provision of two framing signals, DRDY and FSO, ensures that the AD7763 offers flexible data output framing options, which are further enhanced by the availability of the SDL output. The user can select the framing output that best suits the application.
DEVICE ADDRESS 000
AD7763
(000) ADR[2:0] SH[2:0] FSO FSO A
SH[2:0] 100
A
SDO DRDY DRDY
MCLK
MCLK
DEVICE ADDRESS 001
AD7763
(001) ADR[2:0] SH[2:0] FSO FSO B
B
SDO
MCLK
DEVICE ADDRESS 010
AD7763
(010) ADR[2:0] SH[2:0] FSO
SHARED SERIAL DATA OUTPUT (SDO)
FSO C
C
SDO
MCLK
DEVICE ADDRESS 011
AD7763
(011) ADR[2:0] SH[2:0] FSO FSO D
D
SDO
Figure 26. Four AD7763 Devices Sharing the Serial Bus
The active edge of the FSI signal should be set to occur at a position when the SCO signal is high or low and which also allows setup and hold time from the SCO falling edge to be met. The width of the FSI signal can be set to between 1 SCO period and 32 SCO periods wide. A second or subsequent FSI falling edge, which occurs before 32 SCO periods have elapsed, is ignored. Figure 3 also shows the format for the serial data written to the AD7763. A write operation requires 32 bits. The first 16 bits select the device and register address for which the data written is intended. The second 16 bits contain the data for the selected register. When using multiple devices that share the same serial bus, all FSO and SDI pins can be tied together and each device written to individually by setting the appropriate address bits in the serial 32-bit word. The exception to this is when all devices can be written to at the same time by setting the ALL bit to logic high.
WRITING TO THE AD7763
Figure 3 shows the AD7763 write operation. The serial writing operation is synchronous to the SCO signal. The status of the frame sync input, FSI , is checked on the falling edge of the SCO signal. If the FSI line is low, then the first data is latched in on the next SCO falling edge.
Rev. 0 | Page 16 of 32
05476-013
MCLK
AD7763
Thus, if this bit is set to logic high, every device on the serial bus accepts the data written, regardless of the address bits. This feature is particularly attractive if, for example, four devices are being configured with the same user-defined filter. Instead of having to download the filter configuration four times, only one write is required. See the Downloading a User-Defined Filter section for further details. Writing to AD7763 is allowed at any time, even while reading a conversion result. Note that after writing to the devices, valid data is not output until after the settling time for the filter has elapsed. The DVALID status bit is asserted at this point to indicate that the filter has settled and that valid data is available at the output.
READING STATUS AND OTHER REGISTERS
The AD7763 features a number of programmable registers. To read back the contents of these registers or the status register, the user must first write to the control register of the device, setting a bit corresponding to the register to be read. The next read operation then outputs the contents of the selected register instead of a conversion result. To ensure that the next read cycle contains the contents of the register that has been written to, the write operation to the register in question must be completed a minimum of 8 x tSCO before the falling edge of DRDY, which indicates the start of the next read cycle. More information on the relevant bits in the control register is provided in the Registers section.
Rev. 0 | Page 17 of 32
AD7763
READING DATA USING THE I2S INTERFACE
The AD7763 has the capability of operating using an I S interface. The interface is functional only for the output of stereo data and does not apply to writing to control registers, programming coefficients for the digital filter, or the reading of any information contained in the AD7763 onboard registers. All of these operations must be undertaken using the normal serial interface. The I2S interface operates using two AD7763 devices. The pins shown in Table 9 are used as the output pins for the SCK (serial clock), SD (serial data), and WS (word select) signals for the I2S interface. Table 9.
SPI Pins FSO SDO SCO
2 2
LEFT CHANNEL
AD7763
DEVICE ADDRESS 000 1 (000) ADR[2:0] I2S SH[2:0] MCLK SH[2:0] MCLK 001 SD FSO
A
SCO SDO WS SCK 3-WIRE I2S INTERFACE
MCLK SH[2:0] 1 DEVICE ADDRESS 001 I2S ADR[2:0] SDO
B
I S Signals WS SD SCK
2
2
AD7763
RIGHT CHANNEL
05476-026
(001)
To enable the I S interface, the I S pin is set to logic high. The Share Pins SH[2:0] of both AD7763 devices that use the I2S interface are set to 001. The Address Pins ADR[2:0] of the two devices must also be set to 000 and 001, respectively. The WS and SCK signals that are used for the interface can be taken from either AD7763 device. Note that the device that is assigned Address 000 is defined as the left channel, and its data is output on the SD line when WS is logic low. The WS and SCK signals can be taken from the appropriate pins on either of the AD7763 devices using the I2S interface. The SD pins of both devices must be connected together, as shown in Figure 27. Data is clocked out on the SD line in accordance with Figure 28. Because Device A is assigned Address 000, it is defined as the left channel. The 32-bit conversion result from the left channel is clocked out when WS is logic low, with the MSB being clocked out first. Each 32-bit result consists of 24 data bits in twos complement format, followed by eight status bits, as shown in the following bit map.
D7 DVALID D6 OVR D5 UFILTER D4 LPWR D3 FILTER_OK D2 ADR0 D1 0 D0 ThreeState
Figure 27. Two AD7763 Devices Operating Using the I2S Interface
Conversion results from Device B, assigned Address 001, are clocked out on the SD line when WS is logic high. The SD line goes into three-state on the falling edge of the 32nd SCK after the falling edge of WS (left channel data) and also on the falling edge of the 32nd SCK after the rising edge of WS (right channel data). This permits swapping of the SD bus between the left and right channel devices without contention. In decimate x 32 mode the I2S interface is operational only when CDIV = 0 and SCR = 1. The interface operates for all combinations of SCR and CDIV in all other modes of decimation. The DRDY pulse still operates as in the normal serial SPI-type interface, pulsing low immediately prior to the falling edge of WS but having no meaning in the I2S interface specification.
SCK A (O)
WS A (O)
SD (O)
THREESTATE
D23
D22
D21
ST2 LEFT CHANNEL DEVICE A (WORD n)
ST1
THREESTATE
D23
D22
D21
ST2
ST1
THREESTATE
RIGHT CHANNEL DEVICE B (WORD n - 1)
RIGHT CHANNEL DEVICE B (WORD n + 1)
LEFT CHANNEL DEVICE A (WORD n + 2)
05476-027
Figure 28. Timing Diagram for I2S Interface
Rev. 0 | Page 18 of 32
AD7763 CLOCKING THE AD7763
The AD7763 requires an external, low jitter clock source. This signal is applied to the MCLK pin, and the MCLKGND pin is used to sense the ground from the clock source. An internal clock signal (ICLK) is derived from the MCLK input signal. The ICLK controls the internal operations of the AD7763. The maximum ICLK frequency is 20 MHz, but due to an internal clock divider, a range of MCLK frequencies can be used. There are two ways to generate the ICLK:
ICLK = MCLK (CDIV = 1) ICLK = MCLK/2 (CDIV = 0)
EXAMPLE 2
Following is a second example from Table 6, where:
ODR = 48 kHz. fICLK = 12.288 MHz. fIN (maximum) = 19.2 kHz. SNR = 120 dB.
t j (rms ) =
256 = 133 ps 2 x x 19.2 x 103 x 106
This option is pin selectable (Pin 58). On power-up, the default is ICLK = MCLK/2 to ensure that the part can handle the maximum MCLK frequency of 40 MHz. For output data rates equal to those used in audio systems, a 12.288 MHz ICLK frequency can be used. As shown in Table 6, output data rates of 192 kHz, 96 kHz, and 48 kHz are achievable with this ICLK frequency. As mentioned previously, this ICLK frequency can be derived from different MCLK frequencies. The MCLK jitter requirements depend on a number of factors and are determined by
t j(rms ) = OSR
The input amplitude also has an effect on these jitter figures. If, for example, the input level is 3 dB below full scale, the allowable jitter is increased by a factor of 2, increasing the first example to 2.53 ps rms. This happens when the maximum slew rate is decreased by a reduction in amplitude. Figure 29 and Figure 30 illustrate this point, showing the maximum slew rate of a sine wave of the same frequency but with different amplitudes.
1.0
0.5
2 x x f IN x 10
SNR ( dB ) 20
0
Where: OSR = oversampling ratio = f ICLK .
ODR
-0.5
05476-014 05476-015
fIN = maximum input frequency. SNR(dB) = target SNR.
-1.0
Figure 29. Maximum Slew Rate of Sine Wave with Amplitude of 2 V p-p
1.0
EXAMPLE 1
This example is taken from Table 6, where:
ODR = 625 kHz. fICLK = 20 MHz. fIN (maximum) = 250 kHz. SNR = 108 dB.
0.5
0
t j ( rms )
32 = = 3.6 ps 2 x x 250 x 10 3 x 10 6
-0.5
This is the maximum allowable clock jitter for a full-scale, 250 kHz input tone with the given ICLK and output data rate.
-1.0
Figure 30. Maximum Slew Rate of Same Frequency Sine Wave with Amplitude of 1 V p-p
Rev. 0 | Page 19 of 32
AD7763 DRIVING THE AD7763
The AD7763 has an on-chip differential amplifier that operates with a supply voltage (AVDD3) from 3.15 V to 5.25 V. For a 4.096 V reference, the supply voltage must be 5 V. To achieve the specified performance in normal mode, the differential amplifier should be configured as a first-order antialias filter, as shown in Figure 31. Any additional filtering should be carried out in previous stages using low noise, high performance op amps, such as the AD8021. Suitable component values for the first-order filter are shown in Table 10. The values in Table 10 yield a 10 dB attenuation at the first alias point of 19 MHz.
CFB
+2.5V +3.685V 0V A -2.5V +0.410V +2.048V VIN+
+2.5V B 0V
+3.685V
+2.048V
VIN-
-2.5V
+0.410V
Figure 32. Differential Amplifier Signal Conditioning
CFB
RFB 2R A RIN CS B RIN RFB CFB
05476-016
RFB
RM VIN- A1 RM VIN+ VIN
2R RIN AD8021 CS R RIN RFB CFB
05476-018
05476-019
RM VIN- A1 RM VIN+
Figure 31. Differential Amplifier Configuration Figure 33. Single-Ended-to-Differential Conversion
Table 10. Normal Mode Component Values
VREF 4.096 V RIN 1 k RFB 655 RM 18 CS 5.6 pF CFB 33 pF
VIN+ CPA SH1 SS1 CS1 SH3 CPB1 SS3 ANALOG MODULATOR
Figure 32 shows the signal conditioning that occurs using the circuit in Figure 18 with a 2.5 V input signal biased around ground and having the component values and conditions in Table 10. The differential amplifier always biases the output signal to sit on the optimum common mode of VREF/2, in this case, 2.048 V. The signal is also scaled to give the maximum allowable voltage swing with this reference value. This is calculated as 80% of VREF; that is, 0.8 x 4.096 V 3.275 V p-p on each input. To obtain maximum performance from the AD7763, it is advisable to drive the ADC with differential signals. Figure 33 shows how a bipolar, single-ended signal biased around ground can drive the AD7763 with the use of an external op amp, such as the AD8021. With a 4.096 V reference, a 5 V supply must be provided to the reference buffer (AVDD4). With a 2.5 V reference, a 3.3 V supply must be provided to AVDD4.
SS2
CS2 SH4
SH2
CPB2
SS4
Figure 34. Equivalent Input Circuit
The AD7763 employs a double sampling front end, as shown in Figure 34. For simplicity, only the equivalent input circuit for VIN+ is shown. The equivalent input circuitry for VIN- is the same.
Rev. 0 | Page 20 of 32
05476-017
AD7763
Sampling Switch SS1 and Sampling Switch SS3 are driven by ICLK, whereas Sampling Switch SS2 and Sampling Switch SS4 are driven by ICLK. When ICLK is high, the analog input voltage is connected to CS1. On the falling edge of ICLK, the SS1 and SS3 switches open, and the analog input is sampled on CS1. Similarly, when ICLK is low, the analog input voltage is connected to CS2. On the rising edge of ICLK, the SS2 and SS4 switches open, and the analog input is sampled on CS2. Capacitor CPA, Capacitor CPB1, and Capacitor CPB2 represent parasitic capacitances that include the junction capacitances associated with the MOS switches.
Table 11. Equivalent Component Values
Mode Normal Low Power CS1 51 pF 13 pF CS2 51 pF 13 pF CPA 12 pF 12 pF CPB1/CPB2 20 pF 5 pF
The following are conditions for applying the SYNC pulse:
* The issuing of a SYNC pulse to the part must not coincide with a write to the part. * The SYNC pulse should be applied a minimum of 2.5 ICLK cycles after the FSI signal for the previous write to the part has returned to logic high. * Ensure that the SYNC pulse is taken low for a minimum of 2.5 ICLK cycles.
Data can now be read from the part using the default filter, offset, gain, and overrange threshold values. The conversion data read is not valid, however, until the settling time of the filter has passed. When this has occurred, the DVALID bit read is set, indicating that the data is indeed valid. The user can then download a user-defined filter, if required (see Downloading a User-Defined Filter). Values for gain, offset, and overrange threshold registers can also be written or read at this stage.
USING THE AD7763
Following is the recommended sequence for powering up and using the AD7763. 1. Apply power. 2. Start clock oscillator, applying MCLK. 3. Take RESET low for a minimum of 1 MCLK cycle. 4. Wait a minimum of 2 MCLK cycles after RESET has been released. 5. Write to Control Register 2 to power up the ADC and the differential amplifier, as required. 6. Write to Control Register 1 to set up the output data rate. 7. In circumstances where multiple parts are being synchronized, a SYNC pulse must be applied to the parts; otherwise, no SYNC pulse is required.
BIAS RESISTOR SELECTION
The AD7763 requires a resistor to be connected between the RBIAS pin and AGND. The value for this resistor is dependent on the reference voltage being applied to the device. The resistor value should be selected to give a current of 25 A through the resistor to ground. For a 2.5 V reference voltage, the correct resistor value is 100 k; for a 4.096 V reference voltage, the correct resistor value is 160 k.
Rev. 0 | Page 21 of 32
AD7763 DECOUPLING AND LAYOUT RECOMMENDATIONS
Due to the high performance nature of the AD7763, correct decoupling and layout techniques are required to obtain the performance as stated within this data sheet. Figure 35 shows a simplified connection diagram for the AD7763.
PIN 4 PIN 14 PIN 15
PIN 12
PIN 6 PIN 33
PIN 24 PIN 27
PIN 44 PIN 63
PIN 41
4 14 15
12
6 33
24 27
44 63
41
U2 61 I2S 60 SCR 58 CDIV 56 FSO 55 SCO 54 SDO 52 SDI 51 FSI 50 SDL 49 SCP 48 ADR0 47 ADR1 46 ADR2 45 SH0 40 SH1 39 SH2 RESET SYNC DRDY 37 36 38 3 2 I2S SCR CDIV
INA+ INA- OUTA- OUTA+
19 VINA+ 20 VINA- 21 VOUTA- 22 VOUTA+ 8 DECAPA 30 DECAPB 25 VIN+ 26 VIN-
VDRIVE VDRIVE
AVDD2 AVDD2 AVDD2
AVDD4
AVDD1 AVDD1
AVDD3 AVDD2
DVDD
FSO SCO SDO SDI FSI SDL SCP ADR0 ADR1 ADR2 SH0 SH1 SH2 RESET SYNC DRDY MCLK
C7 100nF
C64 33pF
VIN+ VIN-
AD7763BSV
VREF 10 VREF+ 9 REFGND 17 1 35 42 43 53 57 59 62 64 RBIAS DGND DGND DGND DGND DGND DGND DGND DGND DGND
R19 160k
7 AGND1 34 AGND1
AGND2 AGND2 AGND2 AGND2 AGND2
AGND3 AGND3 AGND3 AGND3
11 AGND4
MCLK MCLKGND
5 13 16 18 28
AVDD2
AVDD4 PIN 12 (VBUF) L9 PIN 27
AVDD1
23 29 31 32
AVDD3
VDRIVE
DVDD
L4 L5 R38 10 C59 10nF PIN 5 (VMOD1) PIN 33 (VMOD2) L11 PIN 24 (VDIF1) L6 PIN 44 (VDRV1) L7 PIN 63 (VDRV2) L12 PIN 41 (DVDD) L8
L1 PIN 4 (RHS) PIN 15 (VBIAS)
L3 PIN 14 (LHS)
L2
Figure 35. Simplified Connection Diagram
Rev. 0 | Page 22 of 32
05476-028
C48 100nF
C50 100nF
C62 100nF
C52 100nF
C53 100nF
C54 100nF
C56 100nF
C57 100nF
C58 100nF
AD7763
SUPPLY DECOUPLING
Every supply pin must be connected to the appropriate supply via a ferrite bead and decoupled to the correct ground pin with a 100 nF, 0603 case size, X7R dielectric capacitor. There are two exceptions
* Pin 12 (AVDD4) must have a 10 resistor inserted between the pin and a 10 nF decoupling capacitor. * Pin 27 (AVDD2) does not require a separate decoupling capacitor or a direct connection to the supply; instead, it is connected to Pin 14 via an 8.2 nH inductor.
DIFFERENTIAL AMPLIFIER COMPONENTS
The correct components for use around the on-chip differential amplifier are shown in Table 10. Matching the components on both sides of the differential amplifier is important to minimize distortion of the signal applied to the amplifier. A tolerance of 0.1% or better is required for these components. Symmetrical routing of the tracks on both sides of the differential amplifier also assists in achieving stated performance.
EXPOSED PADDLE
The AD7763 64-lead TQFP_EP employs a 6 mm x 6 mm exposed paddle (see Figure 39). The paddle reduces the thermal resistance of the package by providing a path of low thermal resistance to the PCB and, in turn, increases the heat transfer efficiency from the AD7763 package. Soldering the exposed paddle to the AGND plane of the PCB is fundamental in creating the conditions that allow the AD7763 package to perform to the highest specifications possible.
The ferrite beads that are used to connect each supply pin to the appropriate power supply should have a characteristic impedance of 600 to 1 M at frequencies around 100 MHz, a dc impedance of 1 or less, and a rated current of 200 mA.
ADDITIONAL DECOUPLING
There are two other decoupling pins on the AD7763: Pin 8 (DECAPA) and Pin 30 (DECAPB). Pin 8 should be decoupled with a 100 nF capacitor, and Pin 30 requires a 33 pF capacitor.
LAYOUT CONSIDERATIONS
While using the correct components is essential to achieve optimum performance, the correct layout is just as important. The Design Tools section of the AD7763 product page on the Analog Devices website contains the Gerber files for the AD7763 evaluation board. These files should be used as a reference when designing any system using the AD7763. The location and orientation of some of the components mentioned in previous sections are critical, and particular attention must be paid to the components that are located close to the AD7763. Locating these components farther away from the devices can have a direct impact on the maximum performance achievable.
REFERENCE VOLTAGE FILTERING
A low noise reference source, such as the ADR431 (2.5 V) or ADR434 (4.096 V), is suitable for use with the AD7763. The reference voltage supplied to the AD7763 should be decoupled and filtered, as shown in Figure 36. The recommended scheme for the reference voltage supply is a 100 series resistor connected to a 100 F tantalum capacitor, followed by a series resistor of 10 , and finally, a 10 nF decoupling capacitor very close to the VREF pin.
U3 ADR434 12V C15 10F + C9 100nF 2 +VIN VOUT GND 4 6 C10 100nF R30 100 + R17 10 PIN 10 C11 100F C46 10nF
Figure 36. Reference Connection
The use of ground planes should also be carefully considered. To ensure that the return currents through the decoupling capacitors are flowing to the correct ground pin, the ground side of the capacitors should be as close as possible to the ground pin associated with that supply. A ground plane should not be relied upon as the sole return path for decoupling capacitors, because the return current path using ground planes is not easily predicted.
Rev. 0 | Page 23 of 32
05476-021
AD7763 PROGRAMMABLE FIR FILTER
As discussed in the Theory of Operation section, the third FIR filter on the AD7763 can be programmed by the user. The default coefficients that are loaded on reset are shown in Table 12. This gives the frequency response shown in Figure 37. The frequencies shown in Figure 37 scale directly with the output data rate.
Table 12. Default Filter Coefficients
# 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Decimal Value +53656736 +25142688 -4497814 -11935847 -1313841 +6976334 +3268059 -3794610 -3747402 +1509849 +3428088 +80255 -2672124 -1056628 +1741563 +1502200 -835960 -1528400 +93626 +1269502 +411245 -864038 -664622 +434489 Hex Value 332BCA0 17FA5A0 444A196 4B62067 4140C31 6A734E 31DDDB 439E6B2 4392E4A 1709D9 344EF8 1397F 428C5FC 4101F74 1A92FB 16EBF8 40CC178 4175250 16DBA 135EFE 6466D 40D2F26 40A242E 6A139 # 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 Decimal Value +700847 -70922 -583959 -175934 +388667 +294000 -183250 -302597 +16034 +238315 +88266 -143205 -128919 +51794 +121875 +16426 -90524 -63899 +45234 +114720 +102357 +52669 +15559 +1963 Hex Value AB1AF 401150A 408E917 402AF3E 5EE3B 47C70 402CBD2 4049E05 3EA2 3A2EB 158CA 4022F65 401F797 CA52 1DC13 402A 401619C 400F99B B0B2 1C020 18FD5 CDBD 3CC7 7AB
To create a user-defined filter, note the following:
* The filter must be even, symmetrical FIR. * The coefficients are 27 bits in length. All coefficients are in sign-and-magnitude format. The sign bit coded as positive = 0 is followed by 26 magnitude bits. * The filter length must be between 12 taps and 96 taps in steps of 12. * Because the filter is symmetrical, the number of coefficients that must be downloaded is half the filter length. The default filter coefficients are an example of this, with only 48 coefficients listed for a 96-tap filter. * Coefficients are written from the center of impulse response (adjacent to the point of symmetry) outward. * The coefficients are scaled so that the in-band gain of the filter is equal to 134217726, with the coefficients rounded to the nearest integer. For a low-pass filter, this is the equivalent of having the coefficients sum arithmetically (including sign) to +67108863 (0x3FFFFFF) positive value over the half-impulse-response coefficient set (maximum 48 coefficients). Any deviation from this results in the introduction of a gain error.
0 -20 -40
AMPLITUDE (dB)
PASS-BAND RIPPLE = 0.05dB -0.1dB FREQUENCY = 251kHz -3dB FREQUENCY = 256kHz STOP BAND = 312.5kHz
-60 -80 -100 -120
05476-022
The default filter should be sufficient for most applications. It is a standard brick wall filter with a symmetrical impulse response. The default filter has a length of 96 taps and is nonaliasing, with 120 dB of attenuation at Nyquist. This filter not only performs signal antialiasing but also suppresses out-ofband quantization noise produced by the analog-to-digital conversion process. Any significant relaxation in the stop-band attenuation or transition bandwidth relative to the default filter can result in failure to meet the SNR specifications.
-140 -160 0 100 200 300 400 500 600 FREQUENCY (kHz)
Figure 37. Default Filter Frequency Response (625 kHz ODR)
To download a user-defined filter, see the Downloading a UserDefined Filter section.
Rev. 0 | Page 24 of 32
AD7763 DOWNLOADING A USER-DEFINED FILTER
As discussed in the Programmable FIR Filter section, each of the filter coefficients is 27 bits in length: one sign bit and 26 magnitude bits. To download coefficients for a user-specific FIR filter, a 32-bit word is written to the AD7763 for each coefficient.
D31 ALL D30 ADR2 D29 ADR1 D28 ADR0 D27 0 D26 Sign D[25:0] Magnitude
To download a user-defined filter: 1. Write to Control Register 1, setting the DL Filt bit. The correct Filter Length Bits FLEN[3:0] correspond to the length of the filter about to be downloaded (see Table 13) and the correct decimation rate. Write the 32-bit word (as per format specified). The first coefficient to be written must be the one adjacent to the point of filter symmetry. Repeat Step 2 for each coefficient. Implement the checksum write as per the specified format. Use the following methods to verify that the filter coefficients have been downloaded correctly:
* *
When a user writes coefficients to one device, the address of that particular device (as assigned by the ADR[2:0] pins) must be specified in the bits labeled ADR[2:0]. In a configuration where more than one device shares the same SDI line, setting the ALL bit to logic high and leaving Address Bits ADR[2:0] logic low enables the user to write each coefficient to all devices simultaneously. To ensure that a filter is downloaded correctly, a checksum must be generated and downloaded following the download of the final coefficient. The checksum is a 16-bit word generated by splitting each 32-bit word into 4 bytes and summing all bytes from all coefficients up to a maximum of 192 bytes (maximum number of coefficients = 48 bytes x 4 bytes written for each coefficient). The checksum is written to the device in the form of a 32-bit word in the following format:
D31 ALL D30 ADR2 D29 ADR1 D28 ADR0 D[27:16] 0 D[15:0] Checksum
2.
3. 4. 5.
Read the status register, checking the DL_OK bit. Start reading data and observe the status of the DL_OK bit.
Note that because the user coefficients are stored in RAM, they are cleared after a RESET operation or a loss of power.
Table 13. Filter Length Values
FLEN[3:0] 0000 0001 0011 0101 0111 1001 1011 1101 1111 Number of Coefficients Default 6 12 18 24 30 36 42 48 Filter Length Default 12 24 36 48 60 72 84 96
Note that when writing the checksum, the addressing requirements are as before, and Bit 27 to Bit 16 are all set to 0. The same checksum is generated internally in the AD7763 and compared with the checksum downloaded. The DL_OK bit in the status register is set if these two checksums agree.
Rev. 0 | Page 25 of 32
AD7763
EXAMPLE FILTER DOWNLOAD
The following is an example of downloading a short, user-defined filter with 24 taps. The frequency response is shown in Figure 38.
10 0 -10
Table 15 shows the 32-bit word (as per the format shown in the Downloading a User-Defined Filter section) in hexadecimal for each of the coefficients that must be written to the AD7763 to realize this filter. The table is also split into the bytes that are all summed to produce the checksum. The checksum generated from these coefficients is 0x0E6B.
Table 15. Filter Hex Values 1
Coefficient 1 2 3 4 5 6 7 8 9 10 11 12
1
AMPLITUDE (dB)
-20 -30 -40 -50 -60 -70 -80 0 100 200 300 400 500 600 FREQUENCY (kHz)
05476-023
Figure 38. 24-Tap FIR Frequency Response
The coefficients for the filter in Table 14 are shown from the center of symmetry outward; that is, Coefficient 1 is the coefficient at the center of symmetry. The raw coefficients were generated using a commercial filter design tool and scaled appropriately so their sum equals 67108863 (0x3FF FFFF).
Table 14. 24-Tap FIR Coefficients
Coefficient 1 2 3 4 5 6 7 8 9 10 11 12 Raw +0.365481974 +0.201339905 +0.009636604 -0.075708848 -0.042856209 +0.019944246 +0.036437914 +0.007592007 -0.021556583 -0.024888355 -0.012379538 -0.001905756 Scaled +53188232 +29300796 +1402406 -11017834 -6236822 +2902466 +5302774 +1104856 -3137108 -3621978 -1801582 -277343
32-Bit Word Written to Download Coefficient Byte 1 Byte 2 Byte 3 Byte 4 03 2B 96 88 01 BF 18 3C 00 15 66 26 04 A8 1E 6A 04 5F 2A 96 00 2C 49 C2 00 50 E9 F6 00 10 DB D8 04 2F DE 54 04 37 44 5A 04 1B 7D 6E 04 04 3B 5F
All values of words listed are with reference to writing to one device only (ALL = 0) with Address 000 (as assigned to the device using the ADR[2:0] pins).
Table 16 lists in hexadecimal format the sequence of 32-bit words the user writes to the AD7763 to set up the ADC and download this filter, assuming selection of an output data rate of 625 kHz.
Table 16.
Word1 0x0001807A Description Address of Control Register 1. Control register data. DL filter, set filter length = 24, set output data rate = 625 kHz. First coefficient. Second coefficient. Other coefficients. Twelfth (final) coefficient. Checksum. Wait (0.5 x tICLK x number of unused coefficients) for AD7763 to fill remaining unused coefficients with 0s. Address of Control Register. Control register data. Set read status and maintain filter length and decimation settings. Read contents of status register. Check Bit 7 (DL_OK) to determine that the filter downloaded correctly.
0x032B9688 0x01BF183C ... 0x04043B5F 0x00000E6B
0x0001087A
1
All values of words listed are with reference to writing to one device only (ALL = 0) with Address 000 (as assigned to the device using the ADR[2:0] pins).
Rev. 0 | Page 26 of 32
AD7763 REGISTERS
The AD7763 has a number of user-programmable registers. The control registers are used to set the decimation rate, the filter configuration, the low power option, and the control of the differential amplifier. There are also digital gain, offset, and overrange threshold registers. Writing to these registers involves writing the register address first, followed by a 16-bit data-word. Register addresses, details of individual bits, and default values are shown here.
CONTROL REGISTER 1--ADDRESS 0X001
Default Value 0x001A
MSB DL Filt RD Ovr RD Gain RD Off RD Stat 0 SYNC FLEN3 FLEN2 FLEN1 FLEN0 BYP F3 1 DEC2 DEC1 LSB DEC0
Table 17.
Bit 15 Mnemonic DL Filt 1 Comment Download Filter. Before downloading a user-defined filter, this bit must be set. The filter length bits must also be set at this time. The write operations that follow are interpreted as the user coefficients for the FIR filter until all the coefficients and the checksum have been written. Read Overrange. If this bit is set, the next read operation outputs the contents of the overrange threshold register instead of a conversion result. Read Gain. If this bit is set, the next read operation outputs the contents of the digital gain register. Read Offset. If this bit is set, the next read operation outputs the contents of the digital offset register. Read Status. If this bit is set, the next read operation outputs the contents of the status register. 0 must be written to this bit. Synchronize. Setting this bit initiates an internal synchronization routine. Setting this bit simultaneously on multiple devices synchronizes all filters. Filter Length Bits. These bits must be set when the DL Filt bit is set and before a user-defined filter is downloaded. Bypass Filter 3. If this bit is a 0, Filter 3 (programmable FIR) is bypassed. 1 must be written to this bit. Decimation Rate. These bits set the decimation rate of Filter 2. Writing a value of 0, 1, or 2 corresponds to 4x decimation. A value of 3 corresponds to 8x decimation; a value of 4 corresponds to 16x; and the maximum value of 5 corresponds to 32x decimation.
14 13 12 11 10 9 8 to 5 4 3 2 to 0
RD Ovr1, 2 RD Gain1, 2 RD Off 1, 2 RD Stat1, 2 0 SYNC1 FLEN[3:0] BYP F3 1 DEC[2:0]
1 2
Bit 15 to Bit 9 are all self-clearing bits. Only one of these bits can be set in any write operation, because they all determine the contents of the next operation.
CONTROL REGISTER 2--ADDRESS 0X002
Default Value 0x009B
MSB 0 0 0 0 0 0 0 0 0 0 0 0 PD LPWR 1 LSB D1PD
Table 18.
Bit 3 2 1 0 Mnemonic PD LPWR 1 D1PD Comment Power Down. Setting this bit powers down the AD7763, reducing the power consumption to 6.35 mW. Low Power. If this bit is set, the AD7763 operates in a low power mode. The power consumption is reduced for a 3 dB reduction in noise performance. 1 must be written to this bit. Differential Amplifier Power Down. Setting this bit powers down the on-chip differential amplifier.
Rev. 0 | Page 27 of 32
AD7763
STATUS REGISTER (READ ONLY)
MSB PART 1 PART 0 DIE 2 DIE 1 DIE 0 0 LPWR OVR DL_OK FILTER_OK UFILTER BYP F3 1 DEC2 DEC1 LSB DEC0
Table 19.
Bit 15,14 13 to 11 10 9 8 7 6 5 4 3 2 to 0 Mnemonic PART[1:0] DIE[2:0] 0 LPWR OVR DL_OK FILTER_OK UFILTER BYP F3 1 DEC[2:0] Comment Part Number. These bits are constant for the AD7763. Die Number. These bits reflect the current AD7763 die number for identification purposes within a system. 0 must be written to this bit. Low Power. If the AD7763 is operating in low power mode, this bit is set to 1. If the current analog input exceeds the current overrange threshold, this bit is set. When downloading a user filter to the AD7763, a checksum is generated. This checksum is compared to the one downloaded following the coefficients. If these checksums agree, this bit is set. When a user-defined filter is in use, a checksum is generated when the filter coefficients pass through the filter. This generated checksum is compared to the one downloaded. If they match, this bit is set. If a user-defined filter is in use, this bit is set. Bypass Filter 3. If Filter 3 is bypassed by setting the relevant bit in Control Register 1, this bit is also set. 1 must be written to this bit. Decimation Rate. These bits correspond to the bits set in Control Register 1.
OFFSET REGISTER--ADDRESS 0X003
Non Bit-Mapped, Default Value 0x0000
The offset register uses twos complement notation and is scaled so that 0x7FFF (maximum positive value) and 0x8000 (maximum negative value) correspond to an offset of +0.390625% and -0.390625%, respectively. Offset correction is applied after any gain correction. Using the default gain value of 1.25 and assuming a reference voltage of 4.096 V, the offset correction range is approximately 25 mV.
OVERRANGE REGISTER--ADDRESS 0X005
Non Bit-Mapped, Default Value 0xCCCC
The overrange register value is compared with the output of the first decimation filter to obtain an overload indication with minimum propagation delay. This is prior to any gain scaling or offset adjustment. The default value is 0xCCCC, which corresponds to 80% of VREF (the maximum permitted analog input voltage). Assuming VREF = 4.096 V, the bit is then set when the input voltage exceeds approximately 6.55 V p-p differential. Note that the overrange bit is also set immediately if the analog input voltage exceeds 100% of VREF for more than 4 consecutive samples at the modulator rate.
GAIN REGISTER--ADDRESS 0X004
Non Bit-Mapped, Default Value 0xA000
The gain register is scaled so that 0x8000 corresponds to a gain of 1.0. The default value of this register is 1.25 (0xA000). This gives a full-scale digital output when the input is at 80% of VREF. This ties in with the maximum analog input range of 80% of VREF p-p.
Rev. 0 | Page 28 of 32
AD7763 OUTLINE DIMENSIONS
0.75 0.60 0.45 1.20 MAX
64 1 PIN 1
12.20 12.00 SQ 11.80
49 48 48 49 64 1
TOP VIEW
(PINS DOWN)
10.20 10.00 SQ 9.80
EXPOSED PAD
6.00 BSC SQ
1.05 1.00 0.95
0 MIN
0.15 0.05
SEATING PLANE
0.20 0.09 7 3.5 0 0.08 MAX COPLANARITY
BOTTOM VIEW
(PINS UP) 16 17 32 33 33 32 17 16
VIEW A
0.50 BSC LEAD PITCH
VIEW A
ROTATED 90 CCW
COMPLIANT TO JEDEC STANDARDS MS-026-ACD-HD
0.38 0.32 0.22
Figure 39. 64-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP] (SV-64-2) Dimensions shown in millimeters
ORDERING GUIDE
Model AD7763BSVZ 1 AD7763BSVZ-REEL1 EVAL-AD7763EB
1
Temperature Range -40C to +85C -40C to +85C
Package Description 64-Lead Thin Quad Flat Package, Exposed Pad (TQFP_EP) 64-Lead Thin Quad Flat Package, Exposed Pad (TQFP_EP) Evaluation Board
Package Option SV-64-2 SV-64-2
Z = Pb-free part.
Rev. 0 | Page 29 of 32
AD7763 NOTES
Rev. 0 | Page 30 of 32
AD7763 NOTES
Rev. 0 | Page 31 of 32
AD7763 NOTES
(c) 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05476-0-10/05(0)
Rev. 0 | Page 32 of 32

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