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Tai-1 Microelectronics
www.taimec.com.tw
TMPA401DM
May 25, 2005
15-W MONO CLASS-D AUDIO POWER AMPLIFIER
GENERAL DESCRIPTION
The TMPA401DM is a bridged-tied (BTL) Class-D audio amplifier for driving speakers with high power efficiency. It can drive 4, 6, 8 or 16 speakers. The output power can be up to 15W. No external heat-sink is necessary. The gain of the amplifier is defined by input resistance. The internally fully differential input structure provides good common mode rejection and power supply rejection. Thermal protection and short-circuit protection are
FEATURES
15-W Class-D Output Power efficiency is up to 82% Time delay for de-pop control Thermal Protection Output Pin Short-Circuit Protection (Short to Other Outputs, Short to VCC, Short to Ground) Differential / Single-Ended Input Low Supply Current (5mA Typical at 12V) Low Current in Shutdown Mode (<1A Typical) Separate VCC & PVCC
integrated for safety purpose. The internal de-pop circuitry eliminates pop noise at power-up & shutdown operations.
PACKAGE
TSSOP20 available
APPLICATIONS
LCD Monitors, TVs, DVD Players and Powered Speakers For best performance, please refer to
http://www.taimec.com.tw/data/Tmpa401EVM/TMPA401DMEVM.pdf
for PCB layout.
REFERENCE CIRCUIT
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TOP VIEW
Please email david@taimec.com.tw for complete datasheet.
Tai-1 Microelectronics reserves the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers are responsible for their products and applications using Tai-1 Microelectronics components.
Note that the external components or PCB layout should be designed not to generate abnormal voltages to the chip to prevent from latch up which may cause damage to the device.
Typical Application
PVCC C6 S1 switch J1 VI+ R4 200k PHONEJACK STEREO R1 330 R3 VIR2 R8 0 12k 12k C5 1nF R5 22k R6 22k C1 1uF INP INN 0.1uF VCC J2 R7 100 PVCC 1 VCC 20 PVCC 2 SD 19 OUTP 3 INP 18 OUTP 4 INN 17 AGND PGND 5 16 VDD PGND 6 HF 15 RC OUTN 7 HF 14 AVDD OUTN 8 13 9 VDD PVCC 12 10AGND PVCC 11 D1 DIODE C7 0.1uF L3 33uH 33uH C14 1uF C13 1uF VOP (to 8ohm speaker) L4 D2 DIODE VON + C16 10uF
C2 1uF C3 1uF C4 1uF C9 0.1uF C15 1uF
401DM20
C8 0.1uF +
C10 10uF
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TMPA401DM
May 25, 2005
TERMINAL FUNCTIONS
TERMINAL I/O NAME AGND AVDD HFRC HFVDD INN INP OUTN OUTP PGND PVCC VCC VDD SD PIN NO 5,10 8 7 6 4 3 13,14 17,18 15,16 11,12,19,20 1 9 2 I I O I I O O O I Analog ground 5-V analog power supply De-pop control 2.5-V Reference for convenience of single-ended input Negative differential input Positive differential input Negative output Positive output Power ground Power supply for output MOS (8V to 15V) High-voltage power supply (8V to 15V) 5-V Reference output(25-mA ) Shutdown (Low valid) DESCRIPTION
ABSOLUTE MAXIMUM RATINGS
Over operating free-air temperature range unless otherwise noted(1) In normal mode Supply voltage, PVcc, Vcc In shutdown mode Input voltage, SD Continuous total power dissipation Operating free-air temperature, TA Operating junction temperature, TJ Storage temperature, Tstg -0.3V to 18V -0.3V to 18V -0.3V to Vcc+0.3V V V V
See package dissipation ratings -20 to 85 C -20 to 150 -40 to 150 C C
(1) Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions "is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
RECOMMENDED OPERATING CONDITIONS
MIN
Supply voltage, VCC High-level input voltage, VIH Low-level input voltage, VIL Operating free-air temperature, TA PVCC, VCC SD SD -20 8 2.0 0.8 85
MAX
15
UNIT
V V V C
PACKAGE DISSIPATION RATINGS
PACKGE TSSOP20(FD) DERATING FACTOR 30 mW/ C TA 25 C POWER RATING 3.75W TA = 70 C POWER RATING 2.4W TA = 85 C POWER RATING 1.95W
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TMPA401DM
May 25, 2005
DC CHARACTERISTICS
T A=25 VCC=15V, RL=8 speaker (unless otherwise noted) C, PARAMETER
VOS HFVDD AVDD/VDD ICC ICC(SD) BTL Output offset voltage Half VDD reference output 5-V Regulated voltage Quiescent current (no load) Supply current in shutdown mode
TEST CONDITIONS
INN and INP AC grounded Gain=20dB No load IO=0 to 25mA, SD =High, VCC=8V to 15V SD =High, VCC= 12V SD =High, VCC= 15V SD =0V, VCC= 12V SD =0V, VCC= 15V VCC=15V High side Low side Total Ri=40k Ri=20k Ri=10k Ri= 0k VI =2V( SD ), VCC=8~15V VI =0V( SD ), VCC=8~15V VCC=8~15V IO=1A,
MIN
TYP
25 0.5x AVDD
MAX
100
UNIT
mV V
4.5
5.0 5 8 0.2 0.2 600 500 1100 22 25.5 28 31.5
5.5 10 16 1 1
V mA uA
rds(on)
Drain-source on-state resistance
m
*Gain
Voltage Gain
dB
IIH IIL fOSC Zi
High-level input current Low-level input current Oscillator frequency Input resistance of INN/INP
20 1 200 20 300
uA uA kHz k
750k 600k *Gain= (Vcc=15V) , Gain= (Vcc=12V), Riexternal input resistance of INP/INN inputs Ri + 20K Ri + 20K
AC CHARACTERISTICS
T A=25 VCC=15V, RL=8 speaker (unless otherwise noted) C, PARAMETER TEST CONDITIONS
15V RL=4 12V 15V 12V 15V 12V 15V RL=16 12V
MIN
TYP
Not allowed 10.5 15 9.6 13 8.2 7.8 5 0.4 0.47 0.3 0.42 -70 85 -60 145 25
MAX
UNIT
W
RL=6 PO(max) Maximum continuous output power (r.m.s) at 1kHz RL=8
W
W
W
Vcc=12V, PO=7W, RL=6, f=1kHz Vcc=15V, PO=12W, RL=6, f=1kHz THD+N Total harmonic distortion plus noise Vcc=12V, PO=6W, RL=8, f=1kHz Vcc=15V, PO=9.5W, RL=8, f=1kHz Vn SNR Output noise Signal-to-noise ratio Vcc=12V, Po at THD+N<0.5%, f=1kHz Gain=20dB Maximum output at THD+N0.5, f=1kHz VCC=12V, PO=1W RL=8
%
dB dB dB C C
Crosstalk Crosstalk between outputs Thermal trip point Thermal hysteresis Copyright (c)2004,Tai-1 Microelectronics Corp.
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TMPA401DM
May 25, 2005
20 18 16 Po-Output Power - W 14 12 10 8 6 4 4 5 6 7 8 9 10 RL - Load Impedance-
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DETAILED DESCRIPTION
Efficiency
The output transistors of a class D amplifier act as switches. The power loss is mainly due to the turn on resistance of the output transistors when driving current to the load. As the turn on resistance is so small that the power loss is small and the power efficiency is high. With 8 ohm load the power efficiency can be better than 82%.
PCB layout for power dissipation
No heat sink is necessary for power dissipation. However the PCB layout should be well designed to dissipate heat for high output power. With 80% power efficiency the generated heat when driving 15 watts to the 8 ohm load is about 3.75 watts. The heat can be carried out through the thermal pad of the device to the PCB. To ensure proper dissipation of heat the PCB has to have heat path from the bottom of the device which is soldered to the PCB. The area of the metal on the PCB for heat dissipation should be big enough. It is suggested that both sides of the PCB are used for power dissipation.
Shutdown
The shutdown mode reduces power consumption. A LOW at shutdown pin forces the device in shutdown mode and a HIGH forces the device in normal operating mode. Shutdown mode is useful for power saving when not in use. This function is useful when other devices like earphone amplifier on the same PCB are used but class D amplifier is not necessary.
Pop-less
A soft start capacitor can be added to the HFRC pin. This capacitor introduces delay for the internal circuit to be stable before driving the load. The pop or click noise when power up/down or switching in between shutdown mode can be thus eliminated. The delay time is proportional to the value of the capacitance. It is about 300ms for a capacitor of 1uF.
Differential input VS single ended input
Differential input offers better noise immunity over single ended input. A differential input amplifier suppresses common noise and amplifies the difference voltage at the inputs. For single ended applications just tie the negative input end of the balanced input structure to ground. If external input resistors are used, the negative input has to be grounded with a series resistor of the same value as the positive input to reduce common noise.
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Voltage gain
The voltage gain can be set through input resistance connecting to input pins. Lower input resistance can be used for higher gain. The voltage gain is defined by (800k ohms)/(Ri+20k ohms) at Vcc=15V without loading, where 20k ohms is internal resistance and Ri is external series resistance of the input pin. If Ri is not used (Ri=0 ohm) the voltage gain is (800k ohms)/(20k ohms) or 32dB. Insert Ri if lower gain is preferable. For example if Ri=30k ohms then voltage is (800k ohms)/(30k+20k ohms) or 24dB. For best result the input resistors should be well matched. Matched resistors are also required even for single ended input configuration for low noise.
Input filter
AC coupling capacitors are required to block the DC voltage from the device. They also define the -3db frequency at the low frequency side. The -3db frequency of the low frequency side is f-3db = 1/ (2R C) where C is the AC coupling capacitance and R is the total resistance in series with C. Note that R=Zin(internal resistance) + Rext(external resistance) Also note that the internal input resistance of INN/INP is 20K ohms. In the following diagram Rext=22k ohms, Zin=20k ohms and C=C1=0.47uF. Thus the -3db frequency at the low frequency side is about 8Hz.
inp
R
22k
C1 0.47uF C2 Zin 20k Class-D amplifier C1 0.47uF Zin 20k
inn
R
22k
0.47nF
A bypass capacitor placed in between the positive signal path and negative signal path is to attenuate the high frequencies. It defines the -3bd frequency at the high frequency side. The input filter becomes a band pass filter. The -3db frequency of the high frequency side is f-3db=1/(2RC) where C is the bypass capacitance and R is the total resistance in parallel with C.
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In this example Rext=22k ohms, Zin=20k ohms and C=C2=0.47nF. Thus the -3db frequency at the high frequency side is about 16kHz.
Input filter
Since the input pins of the device have high impedance it is suggested that an input filter is incorporated as shown in the diagram. The AC coupling capacitors are used to block the DC voltage from the device. They also define the -3db frequency at the low frequency side. A bypass capacitor placed in between the positive signal path and negative signal path is to attenuate the high frequencies. It defines the -3db frequency at the high frequency side. The input filter becomes a band pass filter. The -3db frequency of the low frequency side is f-3db = 1/ 2R C where C is the AC coupling capacitance(1uF) and R is the total resistance in series with C. The -3db frequency of the high frequency side is f-3db = 1/ 2R C where C is the bypass capacitance(1nF) and R is the total resistance in parallel with C. Note that there is 20K input resistor integrated in the chip for each input INP/INN.
Output filter
Ferrite bead filter can be used for EMI purpose. The ferrite filter reduces EMI around 1 MHz and higher FCC and CE only test radiated emissions greater than 30 MHz When selecting a . ferrite bead, choose one with high impedance at high frequencies, but low impedance at low frequencies. Use an LC output filter if there are low frequency 1 MHz EMI sensitive circuits and/or there are long wires from the amplifier to the speaker. EMI is also affected by PCB layout and the placement of the surrounding components. The suggested LC values for different speaker impendence are showed in following figures for reference.
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LC Output Filter(1), Speaker Impedance= 4
LC Output Filter(2), Speaker Impedance= 6 & 8
15H Vo+ 0.22 F 15H Vo0.22 F 1 F
LC Output Filter(3), Speaker Impedance= 4
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www.taimec.com.tw 33H Vo+ 0.47 F 33H Vo0.1 F 0.1 F
TMPA401DM
May 25, 2005
LC Output Filter(4), Speaker Impedance= 6 & 8
Ferrite Chip Bead Vo+ Ferrite Chip Bead Vo100pF 100pF
Typical Ferrite Chip Bead Filter Chip bead example KML2012Q102N 1kohms@100MHz, DCR=0.2ohms, I=1A
Over temperature protection
A temperature sensor is built in the device to detect the temperature inside the device. When a high temperature around 145oC and above is detected the switching output signals are disabled to protect the device from over temperature. Automatic recovery circuit enables the device to come back to normal operation when the internal temperature of the device is below around 120oC.
Over current protection
A current detection circuit is built in the device to detect the switching current of the output stages of the device. It disables the device when the current is beyond about 3.5amps. It protects the device when there is an accident short between outputs or between output and power/gnd pins It also protects the device when an abnormal low impedance is tied to the output. High current beyond the specification may potentially causes electron migration and permanently damage the device. Shutdown or power down is necessary to resolve the protection situation. There is no automatic recovery from over current protection.
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Physical Dimensions
(IN MILLIMETERS)
7.72 TYP 4.16 TYP
(1.78 TYP)
0.42 TYP 0.65 TYP
LAND PATTERN
TSSOP20
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IMPORTANT NOTICE
Tai-1 Microelectronics Corp. reserves the right to make changes to its products and services and to discontinue any product or service without notice. Customers should obtain the latest relevant information for reference. Testing and quality control techniques are used to screen the parameters. Testing of all parameters of each product is not necessarily performed.
Tai-1 Microelectronics Corp. assumes no liability for applications assistance or customer product design. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards.
Reproduction of information in data sheets or related documentation is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Tai-1 Microelectronics Corp. is not responsible or liable for such altered documentation.
Resale of Tai-1 Microelectronics Corp. products or services with statements different from the parameters stated by Tai-1 Microelectronics Corp. for that product or service voids all express and any implied warranties. Tai-1 Microelectronics Corp. is not responsible or liable for any such statements.
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