Tai-1 Microelectronics www.taimec.com.tw / TMPA421DS Preliminary www.class-d.com.tw 15W + 6W × 2 Rev.2.0 December 20, 2005 2.1 Channel CLASS-D AUDIO POWER AMPLIFIER GENERAL DESCRIPTION FEATURES The TMPA421DS is a 2.1 Channel Class-D output ♦ Integrated 2.1 channel power amplifier in one audio power amplifier for driving speakers with high power efficiency. The bass output is designed as BTL (Bridge-Tied-Load) for high chip ♦ 15W + 6W × 2 2.1 Channel Class-D Output output power. The right& left channels are ♦ Power efficiency is up to 82% designed as SE (Single-Ended). The outputs are ♦ Convenient gain control able to drive 4Ω, 6Ω, 8Ω or 16Ω speakers. The output power can be up to 15W for bass and 6W ♦ Time delay for de-pop control for either Right or Left channel. No external heat-sink is necessary. ♦ Thermal Protection ♦ Output Pin Short-Circuit Protection (Short to The gain of the amplifier is defined by either gain0/gain1 gain control or by input resistance. Thermal protection and short-circuit protection are integrated for safety purpose. The internal de-pop circuitry eliminates pop noise at power-up & shutdown operations. Other Outputs, Short to VCC, Short to Ground) ♦ Low Quiescent Current (10mA Typical at 12V) ♦ Low Current in Shutdown Mode (<1µA Typical) ♦ Separate VCC & PVCC ♦ Regulated 5-V Supply Output For best performance, please refer to APPLICATIONS http://www.taimec.com.tw/English/EVM.htm TMPA421DS http://www.class-d.com.tw/English/EVM.htm is convenient for 2.1 channel applications. It can be used for LCD Monitors, for PCB layout. TVs, DVD Players, Powered Speakers or any 2.1 channel power amplifiers. PACKAGE TQFP48L available Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 1 Tai-1 Microelectronics www.taimec.com.tw / TMPA421DS Preliminary www.class-d.com.tw Rev.2.0 December 20, 2005 REFERENCE CIRCUIT BOUT- BOUT+ C1 C2 1uF 1uF L5 33uH L6 33uH D1 DIODE D2 PVCC C22 0.1uF C23 0.1uF 48 47 46 45 44 43 42 41 40 39 38 37 + C15 10uF DIODE C18(optional) PVCC 1000uF(16V) + 1 2 3 C5 0.47uF 4 C11 1uF 5 C6 6.8nF 6 C3 6.8nF 7 C12 1uF 8 9 GAINO 10 GAIN1 11 12 SHUT DOWN BASS INPUT SD BINN BINP HFVDDB RIN LIN HFVDD AGND GAINO GAIN1 NC NC NC NC NC AVCC NC NC AGND VDDZ AVDD HFRC AGND NC 421DS 36 35 34 33 32 31 30 29 AVDD 28 27 26 25 VCC + C24 0.1uF C16 10uF C13 1uF + C14 10uF 13 14 15 16 17 18 19 20 21 22 23 24 NC PV CCL PV CCL LO UT LO UT PG NDL PG NDR ROU T ROU T PV CCR PV CCR NC RIGHT INPUT LEFT INPUT C4 0.47uF NC PVCCB PVCCB BOU TN BOU TN PGNDB PGNDB BOU TP BOU TP PVCCB PVCCB NC U1 PVCC C25 0.1uF + C17 10uF D3 C26 0.1uF + C18(optional) 1000uF(16V) PVCC PVCC DIODE VCC R12 100 D4 DIODE L7 33uH L8 33uH C7 C8 1uF 1uF + C28 47uF ROUT + C29 47uF LOUT Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 2 Tai-1 Microelectronics www.taimec.com.tw / Preliminary www.class-d.com.tw TMPA421DS Rev.2.0 December 20, 2005 （Please email [email protected] 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. Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 3 www.taimec.com.tw / TMPA421DS Preliminary Tai-1 Microelectronics www.class-d.com.tw Rev.2.0 December 20, 2005 Typical Application BOUT- BOUT+ C1 C2 1uF(16V) 1uF(16V) L5 33uH L6 33uH D1 DIODE(optional) D2 PVCC C15 + 10uF(16V) C22 0.1uF(16V) PVCC J1 RIN R5 12k R6 22k PHONEJACKSTEREO LIN R10 22k J4 C10 1nF(6.3V) C30 1nF(6.3V) 1 switch S1 2 C4 1uF(6.3V) 3 C5 1uF(6.3V)4 C11 1uF(6.3V) 5 C6 6.8nF(6.3V) 6 C3 6.8nF(6.3V) 7 C12 1uF(6.3V)8 9 J2 SWSPST 10 J3 SWSPST 11 12 AVDD R4 120k SD BINN BINP HFVDDR RIN LIN HFVDDL AGND GAINO GAIN1 NC NC NC NC NC AVCC NC NC AGND VDDZ AVDD HFRC AGND NC 421DS NC PVCCR PVCCR ROUT ROUT PGNDR PGNDL LOUT LOUT PVCCL PVCCL NC SD NC PVCCB PVCCB BOUTN BOUTN PGNDB PGNDB BOUTP BOUTP PVCCB PVCCB NC U1 C9 33nF(6.3V) R8 12k C23 0.1uF(16V) 48 47 46 45 44 43 42 41 40 39 38 37 R9 10k R7 6k DIODE(optional) C18(optional) PVCC 1000uF(25V) + 36 35 34 33 32 31 30 29 28 AVDD 27 26 25 VCC C24 0.1uF(16V) + C16 10uF(16V) C13 1uF(6.3V) C14 10uF(6.3V) 13 14 15 16 17 18 19 20 21 22 23 24 R11 120k R2 330 R3 330 PVCC VR C25 0.1uF(16V) R1 0 D3 + C17 10uF(16V) PVCC C26 0.1uF(16V) + C19(optional) 1000uF(25V) 100 PVCC DIODE(optional) L8 33uH C7 C8 1uF(16V) 1uF(16V) + C28 47uF(16V) ROUT PDF created with pdfFactory trial version www.pdffactory.com D4 DIODE(optional) L7 33uH Copyright ©2005,Tai-1 Microelectronics Corp. VCC R12 + C29 47uF(16V) LOUT 4 www.taimec.com.tw / TMPA421DS Preliminary Tai-1 Microelectronics www.class-d.com.tw Rev.2.0 December 20, 2005 TERMINAL FUNCTIONS TERMINAL NAME HV/LV I/O DESCRIPTION PIN NO AGND 8,26,30 － － AVCC 33 HV － AVDD 28 LV I 5-V voltage HFVDDB 4 LV O 2.5-V Reference for convenience of single-ended bass input HFVDD 7 LV O 2.5-V Reference for convenience of right and left channel inputs HFRC 27 LV O Power up delay LIN 6 LV I Left channel input RIN Analog ground High-voltage power supply (8V to 15V) 5 LV I Right channel input ROUT 20,21 HV O Class-D right channel output LOUT 16,17 HV O Class-D left channel output PGNDR 19 － － Power ground for right channel PGNDL 18 － － Power ground for left channel PGNDB 42,43 － － Power ground for bass PVCCR 22,23 HV － Power supply for right channel PVCCL 14,15 HV － Power supply for left channel PVCCB 38,39,46,47 HV － Power supply for bass BINP 3 LV I BINN 2 LV I Negative differential input for bass BOUTN 44,45 HV O Class-D negative output for bass BOUTP 40,41 HV O Class-D positive output for bass 1 HV I Shutdown (Low valid) SD (8V to 15V) (8V to 15V) (8V to 15V) Positive differential input for bass GAIN0 9 LV I Gain0 control GAIN1 10 LV I Gain1 control 29 LV O 5-V Regulated output (25mA output max.) － － No connection VDDZ 11,12,13,24, NC 25,31,32,34, 35, 36,37,48 ABSOLUTE MAXIMUM RATINGS Over operating free-air temperature range unless otherwise noted(1) In normal mode Supply voltage, PVCCR, PVCCL, AvCC In shutdown mode Input voltage, SD Input voltage, Gain0, Gain1, RIN, LIN, BINP, BINN Continuous total power dissipation Operating free-air temperature, TA -0.3V to 18V V -0.3V to 18V V -0.3V to AVCC+0.3V V -0.3V to 5V V See package dissipation ratings 。C -20 to 85 Operating junction temperature, TJ -20 to 150 Storage temperature, Tstg -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. Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 5 www.taimec.com.tw / TMPA421DS Preliminary Tai-1 Microelectronics www.class-d.com.tw Rev.2.0 December 20, 2005 RECOMMENDED OPERATING CONDITIONS MIN MAX UNIT 8 15 V Supply voltage, VCC PVCCB, PVCCR, PVCCL, AVCC High-level input voltage, V IH SD , Gain0, Gain1 Low-level input voltage, V IL SD , Gain0, Gain1 0.8 VCC=15V, SD =15V 100 High-level input current, IIH VCC=15V, Low-level input current, IIL 2.0 V Gain0=Gain1=5V V uA 5 VCC=15V, SD =0V 0.5 VCC=15V, 0.5 Gain0=Gain1=0V Operating free-air temperature, TA -20 uA 。C 85 PACKAGE DISSIPATION RATINGS PACKGE TQFP48L(FD) DERATING TA ≤ 25。C TA = 70。C TA = 85。C FACTOR POWER RATING POWER RATING POWER RATING 33 mW/。C 4.125W 2.64W 2.15W DC CHARACTERISTICS T A=25。C, VCC=15V, RL=8Ω speaker (unless otherwise noted) PARAMETER │VOS│ VDD/AVDD HFVDD/HFVDDB Half VDD reference output fOSC Oscillator frequency ICC ICC(SD) rds(on) Gainb Gain TEST CONDITIONS Output offset voltage for right/left channel LIN and RIN AC grounded IO=0 to25mA, SD =High, 5-V Regulated output VCC=8V to 15V MIN MAX 30 4.5 5.0 UNIT mV 5.5 V 350 20 30 kHz 0.5× AVDD No load VCC=8-15V SD =High, VCC= 12V Quiescent current (no load) SD =High, VCC= 15V SD =0.8V, VCC= 12V Supply current in shutdown mode SD =0.8V, VCC= 15V High side Drain-source on-state resistance for all VCC=15V IO=1A, output Low side Gain0=High, Gain0=Low, Voltage Gain of bass at Vcc=15V Gain0=High, Gain0=Low, Gain0=High, Gain0=Low, Voltage Gain of bass at Vcc=12V Gain0=High, Gain0=Low, Gain0=High, Gain0=Low, Voltage Gain of bass at Vcc=9v Gain0=High, Gain0=Low, Gain0=High, Voltage Gain of right and left channel at Gain0=Low, Vcc=15V Gain0=High, Gain0=Low, Gain0=High, Voltage Gain of right and left channel at Gain0=Low, Vcc=12V Gain0=High, Gain0=Low, Voltage Gain of right and left channel at Gain0=High, TYP Gain1= High Gain1=High Gain1= Low Gain1= Low Gain1= High Gain1=High Gain1= Low Gain1= Low Gain1= High Gain1=High Gain1= Low Gain1= Low Gain1= High Gain1=High Gain1= Low Gain1= Low Gain1= High Gain1=High Gain1= Low Gain1= Low Gain1= High Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 250 10 16 1 1 600 500 34 28 22 18 32 26 20 16 30 25 19 14 35 29 23 19 33 27 21 17 31 mA uA mΩ dB dB dB dB 6 www.taimec.com.tw / www.class-d.com.tw Rev.2.0 Vcc=9v Zi TMPA421DS Preliminary Tai-1 Microelectronics Gain0=Low, Gain0=High, Gain0=Low, Gain0=High, Gain0=Low, Gain0=High, Gain0=Low, Input resistance ofBINN/BINP/RIN/LIN Gain1=High Gain1= Low Gain1= Low Gain1= High Gain1=High Gain1= Low Gain1= Low December 20, 2005 25 19 15 15 30 60 100 kΩ AC CHARACTERISTICS T A=25。C, VCC=15V, RL=8Ω speaker (unless otherwise noted) PARAMETER TEST CONDITIONS 12V 10 9V 6.22 15V 14.5 12V 9.3 Maximum continuous output power of 9V 5.34 bass (r.m.s) at 1kHz 15V 12.7 RL=6Ω RL=8Ω RL=16Ω RL=4Ω *PO(max) TYP 15 RL=4Ω *PO(max) MIN 15V Maximum continuous output power of right/left channel (r.m.s) at 1kHz RL=6Ω RL=8Ω Vn Output noise SNR Signal-to-noise ratio Crosstalk Crosstalk SE→BTL 12V 8 9V 4.58 15V 7.65 12V 4.8 9V 2.73 15V 6 12V 3.8 9V 2.17 15V 4.6 12V 3.0 9V 1.67 15V 3.75 12V 2.35 9V 1.34 Maximum output at THD+N＜0.5％, f=1kHz Gain0=Gain1=high, VCC=12V, PO(SE)=2W, RL=8Ω Thermal trip point Thermal hysteresis MAX UNIT W W W W W W W -70 dBV 85 dB -70 dB 145 。C 。C 25 For best performance, please refer to http://www.taimec.com.tw/data/Tmpa421EVM/tmpa421dsEVM.pdf for PCB layout. *Important notice：More copper area and vias are required for high output power especially when the total output power is higher than 15W. Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 7 Tai-1 Microelectronics www.taimec.com.tw / Preliminary www.class-d.com.tw TMPA421DS Rev.2.0 December 20, 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 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. 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 SDNB operation can be fixed easily. But for external circuitry the setup time depends on the component values used in the application. Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 8 Preliminary Tai-1 Microelectronics www.taimec.com.tw / www.class-d.com.tw TMPA421DS Rev.2.0 December 20, 2005 Class-D amplifier + 47uF + 13k 13k PVCC For single-ended outputs or right/left channels a build-in voltage divider is to provide half Vcc to the output pin as shown in the above 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 6.5k ohms (13kohms//13kohms) and the capacitance of the output coupling capacitor is 47uF the RC constant is 0.3 seconds. This indicates that the power up delay has to be much longer than 0.3 seconds. Normally a capacitor of 10uF at HFRC pin would provide 2.2 seconds start up delay to save power up pop noise. Above discussion assumes that the separation frequency is 500Hz and the speaker is 8 ohms. If the separation frequency is 200Hz and the speaker is 4 ohms instead then the output coupling capacitance would be changed to 200uF as calculated below. f =1 / (2π x 4 ohms x C) = 200 Hz C = 1 / (2πx 4 ohms x 200 Hz ) = 200 uF In this case the RC constant of the charging circuit is 6.5 k ohms x 200uF = 1.3 seconds To save pop noise the start up delay time should be much longer than 1.3 seconds. A capacitance of 47 uF would provide 9.4 seconds delay. For frequency separation please refer to “Band pass filter for frequency separation of bass and R/L channels”. 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 Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 9 Tai-1 Microelectronics www.taimec.com.tw / Preliminary www.class-d.com.tw TMPA421DS Rev.2.0 December 20, 2005 that is t = - RC In（0.5）= （320k × 10u） （0.693） = 2.2 seconds The delay time changes linearly with capacitance at HFRC. So a 10uF capacitance will provide about 2.2 seconds delay. 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. Band pass filter for frequency separation of bass and R/L channels For best sound effect the frequency of bass and R/L channels has to be separated. The bass channel amplifies the lower frequencies while the R/L channels amplify the higher frequencies. The power is saved not to drive bass speaker with high frequencies and not to drive R/L channel speakers with low frequencies. The noise level can be reduced as well. Typically the frequency boundary of bass and R/L channels is set 500 Hz and the output power of bass is set around 3~5 times of the R/L channels. Note that different applications may have different requirement for these values. Please refer to EVM documentation if the separation frequency is 200 Hz instead. Bass channel filter If the audio source is stereo (right channel signal and left channel signal) one can generate audio source for bass amplifier by mixing right and left signals and in the mean time filter out frequencies above 500 Hz. A typical application is shown below. Note that Zin=15k ohms is the internal resistance of the class-D amplifier when gain0=gain1=High. Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 10 www.taimec.com.tw / TMPA421DS Preliminary Tai-1 Microelectronics www.class-d.com.tw Rev.2.0 Rin R1 12k Lin R1 December 20, 2005 Cin 12k 0.47uF C1 37nF (R1)/2 12k//12k Zin 15k Class-D amplifier Cin 0.47uF Zin 15k The -3db frequency at high frequency corner is f-3db = 1/ (2πR C) where R=2(Zin // (R1)/2) and C=C1. With specified values f-3db = 500Hz. The -3db frequency at low frequency corner is calculated as f-3db = 1/ (2πR C) where R=Zin + (R1)/2 and C=Cin. With specified values f-3db = 16Hz. Right and Left channel filters To block frequencies below 500Hz, a typical application is shown below. Rin Lin R1 C1 22k R1 22k C2 8.6nF 0.9nF C1 Zin C2 8.6nF 0.9nF Zin 15k Class-Damplifier 15k The -3db frequency at low frequency corner is f-3db = 1/ (2πR C) where R=Zin + R1 and C=C1. With specified values f-3db = 500Hz. The -3db frequency at high frequency corner is f-3db = 1/ (2πR C) where R=Zin // R1 and C=C2. With specified values f-3db = 20kHz. Note that if gain0 and gain1 are set at different states the internal input resistance is changed accordingly. Please refer to DC CHARACTERISTICS for detail. As such the filters should be redesigned to meet the 500 Hz frequency boundary. Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 11 www.taimec.com.tw / TMPA421DS Preliminary Tai-1 Microelectronics www.class-d.com.tw Rev.2.0 December 20, 2005 Voltage gain The voltage gain can be set through gain0/gain1 control or by external input resistors connecting to input pins. If external resistors are used for BINP and BINN of bass channel then these input resistors should be well matched. Well matched resistors are also required even for single ended input configuration for low noise. Suppose the external input resistors Rext are used then the voltage gain is roughly Av=750k ohm / (Rext+15k ohm) for gain0=gain1=High Where 15k ohm is the internal resistance of the input pins. For other gain0/gain1 states please refer to DC CHARACTERISTICS for different input resistance. Power ratio of bass channel and right/left channels The output power ratio of bass to R/L channels is normally set 3~5. However different music has different stress in different frequency range. It becomes difficult to define a fix voltage gain for different applications and to maintain the requirement of bass to R/L ratio. A convenient way of controlling the ratio is to make bass adjustable relative to R/L channels. An easier way is to use VR as shown below. Rin VR R1 12k Lin VR R1 12k Cin BINP 0.47uF Cin 6k Zin BINN 0.47uF Zin Bass amplifier Another way is to use frequency synthesizer to preset voltage gain for different frequency range for particular music content. For simply applications an example is given below to show 3X ratio between bass output power and R/L output power. For Vcc=15v and 8ohm load the voltage gain of the bass channel is around 32. If the power 3 =1.732 and the gain of the R/L channel is 18.5. The voltage gain of the R/L channels is roughly defined as ratio is 3 then the voltage ratio is Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 12 Tai-1 Microelectronics www.taimec.com.tw / TMPA421DS Preliminary www.class-d.com.tw Rev.2.0 December 20, 2005 (750k ohms)/(Ri+15k ohms) resulting Ri= 25.5k ohms. To meet the -3db frequency of the R/L channels which is 500Hz, the filter capacitance should be adjusted to C= 1/(2π x (25.5k+15k ohms) x 500Hz) = 7.86nF. For higher output power one can consider to use 4 ohm speaker for bass and 8 ohm speakers for R/L channels. Suppose the power ratio is set 5X, then the voltage ratio is 5 / 2 =1.58. For Vcc=15v and 4ohm load the voltage gain of the bass channel is around 30. Thus the gain of the R/L channel is 19. The voltage gain of the R/L channels is defined as (750k ohms)/(Ri+15k ohms) resulting Ri= 24.5kohms . To meet the -3db frequency of the R/L channels which is 500Hz, the filter capacitance should be adjusted to C= 1/(2π x (24.5+15k ohms) x 500) = 8nF. Note that the formula for voltage gain varies with supply voltage and loading. But the procedure is to find out the value of Ri before the capacitance is determined. Output coupling capacitor The speaker of the bass channel is tied as BTL. There is no need to have an output capacitor at the output end. But for right and left channels coupling capacitors are required to block DC from the speakers. Since the right and left channels do not amplify frequencies below 500Hz the output coupling capacitance does not have to be big. One can choose the -3db frequency of the output coupling stage to be 200Hz, not too high to attenuate voltage at 500Hz, then the coupling capacitance is C= 1/(2πx 8 ohm x 200Hz) =100uF for 8 ohm load. or C= 1/(2πx 4 ohm x 200Hz) =200uF for 4 ohm load. Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 13 Tai-1 Microelectronics www.taimec.com.tw / Preliminary www.class-d.com.tw TMPA421DS Rev.2.0 December 20, 2005 Input filter In case band pass filter for frequency separation of bass and R/L channels is not used, the AC coupling capacitors are still 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/ (2πR 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 input resistance of BINN/BINP/LIN/RIN is 15K ohms at Gain0=Gain1=high. Please refer to DC CHARACTERISTICS for detail. 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. For BTL output the suggested LC values for different speaker impendence are showed in following figures. LC Output Filter, Speaker Impedance= 4Ω Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 14 Tai-1 Microelectronics www.taimec.com.tw / Preliminary www.class-d.com.tw TMPA421DS Rev.2.0 December 20, 2005 LC Output Filter, Speaker Impedance=6Ω & 8Ω 15μH Vo+ 0.22μ F 15μH 1μ F Vo0.22μ F LC Output Filter, Speaker Impedance=4Ω 33μH Vo+ 0.47μ F 0.1μ F 33μH Vo0.1μ F LC Output Filter, Speaker Impedance=6Ω & 8Ω Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 15 Tai-1 Microelectronics www.taimec.com.tw / Preliminary www.class-d.com.tw TMPA421DS Rev.2.0 December 20, 2005 Ferrite Chip Bead Vo+ Ferrite Chip Bead 100pF Vo100pF Typical Ferrite Chip Bead Filter （Chip bead example：遠越科技 KML2012Q102N 1kohms@100MHz, DCR=0.2ohms, I=1A） For single-ended output the suggested LC values for different speaker impendence are showed in following figures. LC Output Filter, Speaker Impedance= 4Ω LC Output Filter, Speaker Impedance= 6Ω & 8Ω Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 16 Tai-1 Microelectronics www.taimec.com.tw / Preliminary www.class-d.com.tw TMPA421DS Rev.2.0 December 20, 2005 Typical Ferrite Chip Bead Filter （Chip bead example：遠越科技 KML2012Q102N 1kohms@100MHz, DCR=0.2ohms, I=1A） 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 by loud noise, a resistor has to be put in series with the earphone speaker. Typically a resistor of 330 ohms is adequate for this purpose. Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 17 Tai-1 Microelectronics www.taimec.com.tw / Preliminary www.class-d.com.tw TMPA421DS Rev.2.0 December 20, 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 a pulse current beyond 8 amps is detected. 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. Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 18 www.taimec.com.tw / TMPA421DS Preliminary Tai-1 Microelectronics www.class-d.com.tw Rev.2.0 Physical Dimensions SYMBOLS A A1 A2 b C D1 D E1 E e L L1 ccc MIN. 0.00 0.95 0.17 0.09 6.90 8.80 6.90 8.80 0.45 - December 20, 2005 ( IN MILLIMETERS) NDM. 1.00 0.22 7.00 9.00 7.00 9.00 0.50(TYP) 0.60 1.00(REF) - MAX. 1.15 0.10 1.05 0.27 0.20 7.10 9.20 7.10 9.20 0.75 0.08 TQFP48 Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 19 Tai-1 Microelectronics www.taimec.com.tw / Preliminary www.class-d.com.tw TMPA421DS Rev.2.0 December 20, 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. Copyright ©2005,Tai-1 Microelectronics Corp. Copyright ©2005,Tai-1 Microelectronics Corp. PDF created with pdfFactory trial version www.pdffactory.com 20