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Tai-1 Microelectronics
www.taimec.com.tw / www.class-d.com.tw
Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
6W/Ch STEREO CLASS-D AUDIO POWER AMPLIFIER
GENERAL DESCRIPTION
The TMPA402DS is a Single-ended (SE) output Class-D audio power amplifier for driving speakers with high power efficiency. It is able to drive 4, 6, 8 or 16 speakers. The output power can be up to 6W per channel. No external heat-sink is necessary. The gain of the amplifier can be changed by adding external input resistance. Thermal protection and short-circuit protection are
FEATURES
6W/Ch Stereo 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) Low Quiescent Current (5mA Typical at 12V) Low Current in Shutdown Mode (<1A Typical) Separate VCC & PVCC
integrated for safety purpose. The internal depop circuitry eliminates pop noise at power-up & shutdown operations.
APPLICATIONS
LCD Monitors, TVs, DVD Players and Powered Speakers
PACKAGE
TSSOP20 available
For best performance, please refer to
http://www.taimec.com.tw/English/EVM.htm http://www.class-d.com.tw/English/EVM.htm
for PCB layout.
REFERENCE CIRCUIT
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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
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 0.1uF + VCC J2 C5 1nF R3 VIR2 12k C17 1nF R6 22k C2 1uF C3 1uF R8 330 C4 10uF C9 0.1uF + 12k R5 22k R7 100 1 VCC PVCC 20 2 SDB PVCC 19 3 INR OUTR 18 4 INL OUTR 17 AGND PGND 5 16 PGND 6 HFVDD 15 7 HFRC OUTL 14 8 AVDD OUTL 13 VDD PVCC 9 12 10AGND PVCC 11 C7 0.1uF L3 15uH + L4 D2 DIODE 15uH C14 2.2uF R11 2k R12 2k C18 1000uF + 4 ohm PVCC C15 1uF 200k INP INN R1 330 S1 switch J1 VI+ C6 C16 10uF D1 DIODE R9 2k R10 2k + C19 1000uF + 4 ohm PVCC
C13 2.2uF
R4 C1 1uF
PHONEJACK STEREO
402DS
C8 0.1uF +
C10 10uF
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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
TERMINAL FUNCTIONS
TERMINAL I/O NAME AGND AVDD HFRC HFVDD INL INR 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 O 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 Input voltage, INR, INL 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 -0.3V to 5V V 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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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
DC CHARACTERISTICS
T A=25 VCC=15V, RL=8 speaker (unless otherwise noted) C, PARAMETER
VOS HFVDD AVDD/VDD ICC ICC(SD) rds(on) Output offset voltage Half VDD reference output 5-V Regulated voltage Quiescent current (no load) Supply current in shutdown mode Drain-source on-state resistance
TEST CONDITIONS
INL and INR 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 IO=1A, Ri=40k Ri=20k Ri=10k Ri= 0k VI =2V( SD ), VCC=8~15V VI =0V( SD ), VCC=8~15V VCC=8~15V High side Low side
MIN
TYP
80 0.5x AVDD
MAX
UNIT
mV V
4.5
5.0 5 8 0.2 0.2 600 500 22 25.5 28 31.5
5.5 10 16 1 1
V mA uA m
*Gain
Voltage Gain
dB
IIH IIL fOSC Zi
High-level input current Low-level input current Oscillator frequency Input resistance of INR/INL
20 1 200 20 300
uA uA kHz k
*Gain= 750k Ri + 20K
(Vcc=15V) ,
Gain= 600k Ri + 20K
(Vcc=12V),
Riexternal input resistance of INR/INL inputs
AC CHARACTERISTICS
T A=25 VCC=15V, RL=8 speaker (unless otherwise noted) C, PARAMETER
PO(max) Maximum continuous output power (r.m.s) per channel at 1kHz
TEST CONDITIONS
RL=4 RL=6 RL=8 Vcc=12V, PO=4W, RL=4, f=1kHz
MIN
TYP
6 4.6 3.75 0.4 0.47 -70 85 -60 145 25
MAX
UNIT
W W W % dB dB dB C C
THD+N Vn SNR
Total harmonic distortion plus noise Output noise Signal-to-noise ratio
Vcc=15V, PO=5W, RL=4, f=1kHz 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
Crosstalk Crosstalk between outputs Thermal trip point Thermal hysteresis
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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
7 6 Po-O utput Power - W 5 4 3 2 1 4
TA=25 10% THD Maximum Vcc=15V
Vcc=12V
5
6
7
8
9
10
RL - Load Impedance-
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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
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 80%.
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 12 watts to the 8 ohm load is about 3 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. Internal circuit for shutdown is shown below.
Pop-less
A soft start capacitor can be added to the HFRC pin. This capacitor introduced delay for the circuit to be stable before driving the load. The set up time for internal circuit to be stable is quite fast, typically it is less than 100ms. Thus the pop noise caused by shutdown operation
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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
can be fixed easily. But for external circuitry the setup time depends on the component values used in the application. For single-ended outputs a voltage divider is to provide half Vcc to the output pin as shown in the following diagram. During power up this divider is to pre-charge output capacitor to half Vcc before output signal is enabled to drive the speaker. Since the equivalent resistance of the voltage divider is 1k ohms (2kohms//2kohms) and the capacitance of the output coupling capacitor is 1000uF the RC constant is 1 second. This indicates that the power up delay has to be much longer than 1 second. Normally a capacitor of 10uF would provide enough delay time to save power up noise.
+ 1000uF + 2k 2k 4 ohm PVCC
HFRC
HFRC provides a way of soft start up delay. A half_Vcc voltage detector is integrated to detect a RC charge up. The resistor of 320k ohms of the RC circuit is also integrated in the chip but the capacitor is externally hooked up. For C=10uF the half_Vcc delay is 1-e-t/RC=0.5 or e-t/RC=0.5 that is t = - RC In0.5= 320k x 10u 0.693 = 2.2 seconds
To further reduce pop noise one can apply 22uF instead of 10uF at HFRC. But the delay time becomes 4.8 seconds
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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
Voltage gain
The voltage gain can be set through external resistance connecting to input pins. Higher external resistance can be used for lower gain. The formula for voltage gain is defined in the datasheet. The voltage gain of the amplifier by itself is 40 at Vcc=15v. If for some reason the voltage gain has to be reduced an external resistor can be added in series with the input signal. The formula for voltage gain at Vcc=15v becomes gain = 800k ohms/(Zi + Rext) where Zi(=20k ohms) is the internal resistance of the amplifier and Rext is the external added resistance. Without Rext(Rext=0 ohm) the voltage gain is 800k/20k=40. If Rext is 30K ohms then the voltage gain is 800k/(20k+30k)=16. The voltage gain is pretty much proportional to supply voltage. For example the formula for Vcc=12v is gain = 640k ohms/(Zi + Rext)
Input filter
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. Since the input pins of the device have high impedance an input filter, if required, can be incorporated as shown in the application. A bypass capacitor placed in between the input signal path and ground is to attenuate the high frequencies. It defines the -3db frequency at the high 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. The -3db frequency of the high frequency side is f-3db = 1/ 2R C where C is the bypass capacitance and R is the total resistance in parallel with C. Note that there is 20K internal resistor integrated in the chip for each input INR/INL.
Output coupling capacitor
Since the output is singled-ended, coupling capacitor is required to isolate DC voltage between output pin and its corresponding speaker. If the -3db frequency of the output coupling stage is set 20Hz then the coupling capacitance is C= 1/(2x 8 ohm x 20Hz) =1000uF for 8 ohm load.
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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
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.
LC Output Filter(1), Speaker Impedance= 4
LC Output Filter(2), Speaker Impedance= 6 & 8
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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
EARPHONE USE
Class-D output can be used to drive earphone. However to avoid high power to overdrive earphone and to prevent human ear to accidentally be hurt, a resistor has to be put in series with the earphone speaker. Typically a resistor of 330 ohms is adequate for this purpose.
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.
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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
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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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
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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Preliminary
TMPA402DS
Rev.2.0 November 21, 2005
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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