TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 Ideal for Notebook PCs and USB-Powered DAP PACKAGE (TOP VIEW) Speakers 2 W Into 4 Ω From 5-V Supply Integrated Class-AB Headphone Amplifier Second-Generation Modulation Technique – Filterless Operation – Improved Efficiency Low Supply Current . . . 9 mA typ at 5 V Shutdown Control . . . < 0.05 µA Typ Shutdown Pin Is TTL Compatible –40°C to 85°C Operating Temperature Range Space-Saving, Thermally-Enhanced MicroStar BGA and PowerPAD Packaging description LINN LINP HPLIN GAIN0 GAIN1 PVDDL LOUTP PGNDL PGNDL LOUTN PVDDL HPLGAIN HPLOUT MODE HPRGAIN HPROUT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 RINN RINP HPRIN BYPASS SHUTDOWN PVDDR ROUTP PGNDR PGNDR ROUTN PVDDR NC VDD COSC ROSC AGND NC – No internal connection The TPA2000D4 is a 2-W stereo bridge-tied-load (BTL) class-D amplifier designed to drive speakers with as low as 4-Ω impedance. The amplifier uses TI’s second-generation modulation technique, which results in improved efficiency and SNR, and also allows the device to be connected directly to the speaker without the use of the LC output filter commonly associated with class-D amplifiers (this will result in an EMI which must be shielded at the system level). These features make the device ideal for use in notebook PCs where high-efficiency is needed to extend battery run-time. For speakers powered off the USB bus, the high-efficiency allows for higher output power levels without tripping the USB’s over-current circuitry. The gain of the amplifier is controlled by two input terminals, GAIN1, and GAIN0. This allows the amplifier to be configured for a gain of 5, 11, 17 and 23 dB. The differential input terminals are high-impedance CMOS inputs, and can be used as summing nodes. The headphone amplifier is a stereo single-ended (SE) class-AB amplifier which requires two external resistors per channel to set the gain. The MODE pin selects which amplifier is active; the unused amplifier is placed in shutdown to reduce supply current. Both the class-D BTL amplifier, and the class-AB SE amplifier include depop circuitry to reduce the amount of turnon pop at power up, when cycling SHUTDOWN, and when switching modes of operation. The TPA2000D4 is available in the 32-pin thermally-enhanced TSSOP package (DAP) and TI’s new MicroStar BGA package which is thermally-enhanced to allow stereo 2-W continuous output power levels in 4-Ω loads when placed on a board with proper thermal board design. The TPA2000D4 operates over an ambient temperature range of –40°C to 85°C. These thermally-enhanced packages deliver levels of thermal performance that were previously only achievable in TO-220-type packages. Thermal impedances of less than 35°C/W are readily realized in multilayer PCB applications when using the DAP package. Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. †This package is in the PRODUCT PREVIEW stage of development. MicroStar and PowerPAD are trademarks of Texas Instruments. Copyright 2000, Texas Instruments Incorporated This document contains information on products in more than one phase of development. The status of each device is indicated on the page(s) specifying its electrical characteristics. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 AVAILABLE OPTIONS PACKAGED DEVICE TA TSSOP (DAP)† MicroStar BGA (GQC) –40°C to 85°C TPA2000D4DAP TPA2000D4GQC † The DAP package is available taped and reeled. To order a taped and reeled part, add the suffix R to the part number (e.g., TPA2000D4DAPR). functional schematic VDD AGND PVDDR VDD Rin2 RINN Rs2 Gain Adjust 100 Ω 100 Ω + _ _ Deglitch Logic Gate Drive ROUTN + _ PGNDR + _ cmv + Rin1 RINP Gain Adjust 100 Ω PVDDR _ Rs1 + _ 100 Ω + Deglitch Logic Gate Drive ROUTP PGNDR MODE SD–z GAIN1 GAIN0 SD–z Input Buffers Gain 2 Biases and References Startup Protection Logic Ramp Generator Thermal COSC ROSC VDD ok PVDDL BYPASS Rin1 LINP 100 Ω Gain Adjust Rs1 100 Ω + _ _ Deglitch Logic Gate Drive Rin2 100 Ω Gain Adjust ROUTP + + _ cmv _ + LINN OC Detect OC Detect PGNDL PVDDL Rs2 + _ _ 100 Ω + _ HPLIN BYPASS + Deglitch Logic Gate Drive LOUTN PGNDR HPROUT HPLGAIN _ HPRIN BYPASS + HPRGAIN 2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 HPLOUT TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 Terminal Functions TERMINAL NAME NO. I/O DESCRIPTION AGND 17 I Analog ground BYPASS 29 I Connect capacitor to ground for BYPASS voltage filtering COSC 19 I Connect capacitor to ground to set oscillation frequency GAIN0 4 I Bit 0 of gain control GAIN1 5 I Bit 1 of gain control HPLGAIN 12 I Place RF between pins 12 and 13 HPRGAIN 15 I Place RF between pins 14 and 15 HPLIN 3 I Left HP single-ended (SE) input HPLOUT 13 O Left headphone output HPRIN 30 I Right HP SE input HPROUT 16 O Right headphone output LINN 1 I Left class-D negative differential input LINP 2 I Left class-D positive differential input LOUTP 7 O Left positive bridge-tied load (BTL) output LOUTN 10 O Left negative BTL output MODE 14 I Mode = 1, then HP, Mode = 0, then BTL NC 21 — PGNDL 8, 9 I Left class-D high-current ground PGNDR 24, 25 I Right class-D high-current ground PVDDL 6, 11 I Left class-D high-current power supply PVDDR No connection 22, 27 I Right class-D high power supply ROSC 18 I Connect resistor to ground to set oscillation frequency RINP 31 I Right class-D positive differential signal RINN 32 I Left class-D negative differential signal ROUTN 23 O Right negative BTL output ROUTP 26 O Right positive BTL output SHUTDOWN 28 I Shutdown terminal (negative logic) VDD 20 I Power supply absolute maximum ratings over operating free-air temperature (unless otherwise noted)† Supply voltage, VDD, PVDDL,R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to 5.5 V Input voltage, VI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to VDD+0.3 V Continuous total power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Dissipation Rating Table Operating free-air temperature range, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to 85°C Operating junction temperature range, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to 150°C Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 65°C to 150°C Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C † 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. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 3 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 DISSIPATION RATING TABLE PACKAGE TA ≤ 25°C POWER RATING DERATING FACTOR ABOVE TA = 25°C TA = 70°C POWER RATING TA = 85°C POWER RATING DAP 5.3 W 42.5 mW/°C 3.4 W 2.8 W GQC† TBD TBD TBD TBD † This package is in the PRODUCT PREVIEW stage of development. recommended operating conditions MIN Supply voltage, VDD, PVDD, VCC NOM 3.7 High-level input voltage, VIH MAX 5.5 2 V V Low-level input voltage, VIL Operating free-air temperature, TA UNIT –40 0.8 V 85 °C electrical characteristics over recommended operating free-air temperature range, TA = 25°C, PVDD = 5 V (unless otherwise noted) PARAMETER TEST CONDITIONS |VOS| Output offset voltage (measured differentially) PSRR Power supply rejection ratio | IIH | High-level input current | IIL | Low-level input current IDD Supply Su ly current IDD(SD) VI = 0 V, AV = –2 V/V PVDD = 4.5 V to 5.5 V MIN Class D Headphone MODE = 5 V MAX 15 Class-D 70 PVDD = 4.5 V to 5.5 V Headphone PVDD = 5.5 V, VI = PVDD PVDD = 5.5 V, MODE = 0 V TYP Shutdown mode mV dB 75 VI = 0 V UNIT 1 µA 1 µA 9 12 7 11 0 05 0.05 1 mA µA A operating characteristics, class-D amplifier, TA = 25°C, PVDD = 5 V, RL = 4 Ω, Gain = all gains (unless otherwise noted) PARAMETER TEST CONDITIONS PO THD+N Output power THD = 0.1%, Total harmonic distortion plus noise BOM kSVR Maximum output power bandwidth PO = 1 W,f = 20 Hz to 20 kHz THD = 1% Supply ripple rejection ratio f = 1 kHz, SNR Signal-to-noise ratio Vn ZI Noise output voltage 4 f = 1 kHz CBYPASS = 1 µF CBYPASS = 1 µF, f = 20 Hz to 20 kHz Input impedance MIN TYP 2 • DALLAS, TEXAS 75265 UNIT W < 0.4% 20 kHz 71 dB 85 dB 20 µVRMS kΩ >15 POST OFFICE BOX 655303 MAX TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 operating characteristics, class-D amplifier, TA = 25°C, PVDD = 5 V, RL = 8 Ω, Gain = all gains (unless otherwise noted) PARAMETER TEST CONDITIONS PO THD+N Output power THD = 0.1%, f = 1 kHz Total harmonic distortion plus noise f = 20 Hz to 20 kHz BOM kSVR Maximum output power bandwidth PO = 0.5 W, THD = 1% Supply ripple rejection ratio f = 1 kHz, CBYPASS = 1 µF SNR Signal-to-noise ratio Vn ZI Noise output voltage CBYPASS = 1 µF, MIN TYP MAX 1.5 UNIT W <0.2% f = 20 Hz to 20 kHz Input impedance 20 kHz 71 dB 85 dB 20 µVRMS kΩ >15 operating characteristics, headphone amplifier, TA = 25°C, PVDD = 5 V, RL = 32 Ω, Gain = 1 V/V (unless otherwise noted) PARAMETER TEST CONDITIONS PO THD+N Output power THD = 0.1%, f = 1 kHz Total harmonic distortion plus noise f = 20 Hz to 20 kHz BOM kSVR Maximum output power bandwidth PO = 75 mW, THD = 1% Supply ripple rejection ratio f = 1 kHz, CBYPASS = 1 µF SNR Signal-to-noise ratio Vn Noise output voltage CBYPASS = 1 µF, POST OFFICE BOX 655303 f = 20 Hz to 20 kHz • DALLAS, TEXAS 75265 MIN TYP 90 MAX UNIT mW <0.2% 20 kHz 42 dB 80 dB 20 µVRMS 5 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 TYPICAL CHARACTERISTICS Table of Graphs FIGURE Efficiency vs Output power 2, 3 In-band output spectrum vs Frequency Supply current vs Free-air temperature Total harmonic distortion + noise vs Frequency 6, 7 Total harmonic distortion + noise vs Output power 8, 9 Class-D gain and phase vs Frequency 10 Class-D crosstalk vs Frequency 11 Power dissipation vs Output power 12 FFT at 1.5-W output power vs Frequency 13 Supply voltage rejection ratio vs Frequency 14 Headphone total harmonic distortion + noise vs Frequency 15, 16, 23 Headphone total harmonic distortion + noise vs Output power 17 Closed-loop gain and phase vs Frequency 18 Open-loop gain and phase vs Frequency 19 Headphone crosstalk vs Frequency 20, 25 Headphone integrated noise floor vs Frequency 21 Headphone supply voltage rejection ratio vs Frequency 22 Headphone total harmonic distortion + noise vs Output voltage 24 Headphone supply current vs Output voltage 26 Headphone supply current vs Output power 27 4 5 test set-up for graphs The THD+N measurements shown do not use an LC output filter, but use a low pass filter with a cut-off frequency of 20 kHz so the switching frequency does not dominate the measurement. This is done to ensure that the THD+N measured is just the audible THD+N. The THD+N measurements are shown at the highest gain for worst case. The LC output filter used in the efficiency curves (Figure 2 and 3) is shown in Figure 1. L1 = L2 = 22 µH (DCR = 110 mΩ, Part Number = SCD0703T–220 M–S, Manufacturer = GCI) C1 = C2 = 1 µF The ferrite filter used in the efficiency curves (Figure 2 and 3) is shown in Figure 1, where L is a ferrite bead. L1 = L2 = ferrite bead (part number = 2512067007Y3, manufacturer = Fair-Rite) C1 = C2 = 1 nF L1 OUT+ C1 OUT– L2 C2 Figure 1. Class-D Output Filter 6 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 TYPICAL CHARACTERISTICS EFFICIENCY vs OUTPUT POWER EFFICIENCY vs OUTPUT POWER 90 80 Ferrite Bead Filter LC Filter 80 70 70 No Filter LC Filter 60 Efficiency – % 60 50 40 Class-AB 30 Notebook Speaker 50 40 30 Class–AB 20 20 RL = 8 Ω, Multimedia Speaker VDD = 5 V 10 0 0.2 0.4 0.6 0.8 PO – Output Power – W 1 RL = 3 Ω, Notebook PC Speaker VDD = 5 V 10 0 0 1.2 0 0.5 1 1.5 PO – Output Power – W Figure 2 2 Figure 3 IN-BAND OUTPUT SPECTRUM vs FREQUENCY +0 VDD = 5 V, fIN = fO = 1 kHz, PO = 1.5 W, Bandwidth = 20 Hz to 22 kHz, 16386 Frequency Bins –20 –40 Gain – dB Efficiency – % Ferrite Bead Filter –60 –80 –100 –120 –140 0 2k 4k 6k 8k 10k 12k 14k 16k 18k 20k 22k 24k f – Frequency – Hz Figure 4 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 7 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 TYPICAL CHARACTERISTICS SUPPLY CURRENT vs FREE-AIR TEMPERATURE TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY THD+N – Total Harmonic Distortion + Noise – % 12 HP 10 I DD – Supply Current – mA Class–D 8 6 4 2 0 –50 0 50 100 150 TA – Free-Air Temperature – °C 10 VDD = 5 V, RL = 8 Ω, All Gains 5 2 1 PO = 0.05 W 0.5 PO = 0.25 W 0.2 0.1 PO = 0.5 W .05 .02 .01 200 20 50 100 200 Figure 5 VDD = 5 V, RL = 4 Ω, All Gains THD+N – Total Harmonic Distortion + Noise – % THD+N – Total Harmonic Distortion + Noise – % TOTAL HARMONIC DISTORTION + NOISE vs OUTPUT POWER 10 2 1 PO = 0.1 W 0.5 0.2 0.1 PO = 2 W 0.05 PO = 1.5 W 0.02 0.01 20 50 100 200 500 1 k 2 k f – Frequency – Hz 5 k 10 k 20 k 10 5 VDD = 5 V, RL = 8 Ω, All Gains 2 1 0.5 f = 20 Hz 0.1 0.5 0.2 0.009 10 m f = 20 kHz 20 m 50 m 100 m 200 m 500 m PO – Output Power – W Figure 8 POST OFFICE BOX 655303 f = 1 kHz 0.2 Figure 7 8 5 k 10 k 20 k Figure 6 TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY 5 500 1 k 2 k f – Frequency – Hz • DALLAS, TEXAS 75265 1 1.5 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 TYPICAL CHARACTERISTICS CLASS-D GAIN AND PHASE vs FREQUENCY 5 100 25 10 VDD = 5 V, RL = 4 Ω, All Gains 24 23 60 22 40 f = 20 Hz 0.5 f = 1 kHz 0.2 0.1 0.5 20 21 Phase 20 0 19 –20 18 –40 VDD = 5 V, PO = 1 W, RL = 4 Ω, All Gains 17 f = 20 kHz 0.2 16 0.01 10 m 20 m –60 –80 15 50 m 100 m 200 m 500 m PO – Output Power – W 1 2 20 3 Phase – Degerees 1 50 100 200 500 1 k 2 k –100 5 k 10 k 20 k 40 k f – Frequency – Hz Figure 9 Figure 10 CLASS-D CROSSTALK vs FREQUENCY POWER DISSIPATION vs OUTPUT POWER 0.6 –10 VDD = 5 V, RL = 8 Ω Speaker VDD = 5 V, PO = 1 W RL = 4 Ω, All Gains –30 0.5 Power Dissipation – W –20 Class–D Crosstalk – dB 80 Gain 2 Class–D Gain – dBV THD+N – Total Harmonic Distortion + Noise – % TOTAL HARMONIC DISTORTION + NOISE vs OUTPUT POWER –40 –50 –60 –70 L to R –80 R to L 0.4 0.3 0.2 0.1 –90 –100 0 20 50 100 200 500 1 k 2k 5 k 10 k 20 k 0 0.2 f – Frequency – Hz Figure 11 0.4 0.6 0.8 PO – Output Power – W 1 1.2 Figure 12 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 9 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 TYPICAL CHARACTERISTICS FFT AT 1.5-W OUTPUT POWER vs FREQUENCY 0 VDD = 5 V, f = 1 kHz, PO = 1.5 W, RL = 4 Ω Gain – dBv –20 –40 –60 –80 –100 –120 –140 0 2k 4k 6k 8k 10 k 12 k 14 k f Frequency – Hz 16 k 18 k 20 k 22 k 24 k Figure 13 k SVR– Supply Voltage Rejection Ratio – dB –40 –45 VDD = 5 V, RL = 4 Ω –50 –55 –60 –65 –70 –75 –80 20 100 1k f – Frequency – Hz 10 k 20 k THD+N – Total Harmonic Distortion Distortion + Noise – % HEADPHONE SUPPLY VOLTAGE REJECTION RATIO vs FREQUENCY TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY 10 25 2 VDD = 5 V, RL = 32 Ω, AV = 0 dB 1 0.5 0.2 PO = 50 mW 0.1 PO = 7.5 mW 0.05 0.02 0.01 0.005 0.002 20 PO = 25 mW 50 500 1 k 2 k f – Frequency – Hz Figure 15 Figure 14 10 100 200 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5 k 10 k 20 k TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 HEADPHONE HEADPHONE TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY TOTAL HARMONIC DISTORTION + NOISE vs OUTPUT POWER 10 25 2 VDD = 5 V, RL = 32 Ω, PO = 75 mW 1 AV = 20 dB 0.5 0.2 AV = 6 dB 0.1 0.05 0.02 0.01 AV = 0 dB 0.005 0.002 20 50 100 200 500 1 k 2 k f – Frequency – Hz 5 k 10 k 20 k THD+N – Total Harmonic Distrotion + Noise – % THD+N – Total Harmonic Distortion Distortion + Noise – % TYPICAL CHARACTERISTICS 10 5 VDD = 5 V, RL = 32 Ω, AV = 0 dB 2 1 0.5 0.2 0.1 0.05 f = 100 Hz f = 20 kHz f = 1 kHz 0.02 0.006 0.006 100 µ 200 µ 500 µ 1 m 2 m 5 m 10 m 20 m 50 m 100 m PO – Output Power – W Figure 16 Figure 17 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 11 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 TYPICAL CHARACTERISTICS HEADPHONE CLOSED-LOOP GAIN AND PHASE vs FREQUENCY 0 2 0 –50 –2 –100 –150 –4 Phase –200 –6 VDD = 5 V, PO = 75 mW, RL = 32 Ω, AV = 0 dB –8 –10 100 1k 10 k 100 k f – Frequency – Hz 1M Closed-Loop Phase – Degrees Closed-Loop Gain – dB Gain –250 –300 10 M Figure 18 HEADPHONE OPEN-LOOP GAIN AND PHASE vs FREQUENCY 120 0 VDD = 5 V, No Load 100 Open-Loop Gain – dB Phase 60 –100 40 –150 Gain 20 0 –200 –20 –250 –40 –60 1 10 100 1k 10 k 100 k 1M f – Frequency – Hz Figure 19 12 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 –300 10 M Open-Loop Phase – Degrees –50 80 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 TYPICAL CHARACTERISTICS HEADPHONE CROSSTALK vs FREQUENCY 0 VDD = 5 V, PO = 75 mW, RL = 32 Ω, AV = 0 dB –10 –20 Crosstalk – dBV –30 –40 –50 –60 –70 –80 –90 –100 20 50 100 200 500 1 k 2 k 5 k 10 k 20 k f – Frequency – Hz Figure 20 HEADPHONE INTEGRATED NOISE FLOOR 0 VDD = 5 V, RL = 32 Ω, No Input –20 –40 dBV –60 –80 –100 –120 –140 –160 0 2.5 k 5k 7.5 k 10 k 12.5 k 15 k 17.5 k 20 k 22.5 k f Frequency – Hz Figure 21 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 13 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 TYPICAL CHARACTERISTICS HEADPHONE SUPPLY VOLTAGE REJECTION RATIO vs FREQUENCY k SVR– Supply Voltage Rejection Ratio – dB –10 CB = 0.1 µF –20 CB = 1 µF –30 VDD = 5 V, AV = 0 dB, VO = 1 VRMS, RL = 10 kΩ –40 –50 CB = 2.5 V –60 –70 –80 –90 –100 –110 –120 20 50 100 200 500 1 k 2 k f – Frequency – Hz 5 k 10 k 20 k THD+N – Total Harmonic Distortion Distortion + Noise – % HEADPHONE TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY 10 VDD = 5 V, RL = 10 kΩ, VO = 1 VRMS 5 1 0.5 0.2 0.1 0.05 AV = 20 dB 0.02 AV = 6 dB 0.01 0.005 0.002 AV = 0 dB 0.0008 20 50 HEADPHONE HEADPHONE TOTAL HARMONIC DISTORTION + NOISE vs OUTPUT VOLTAGE CROSSTALK vs FREQUENCY –20 10 5 VDD = 5 V, RL = 10 kΩ, AV = 0 dB VDD = 5 V, VO = 1 VRMS, RL = 10 kΩ, AV = 0 dB –30 –40 1 –50 0.5 0.2 0.1 0.05 f = 100 Hz 0.02 –80 Left to Right –100 0.005 –110 0.002 0.0008 0.1m Right to Left –70 –90 f = 20 kHz 0.01 –60 f = 1 kHz –120 0.2m 0.4m 0.6m 0.8m 1 2 20 50 VO – Output Voltage – V 100 200 500 1 k 2 k f – Frequency – Hz Figure 24 14 5 k 10 k 20 k Figure 23 Crosstalk – dBV THD+N – Total Harmonic Distortion Distortion + Noise – % Figure 22 100 200 500 1 k 2 k f – Frequency – Hz Figure 25 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5 k 10 k 20 k TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 TYPICAL CHARACTERISTICS HEADPHONE HEADPHONE SUPPLY CURRENT vs OUTPUT VOLTAGE SUPPLY CURRENT vs OUTPUT POWER 60 VDD = 5 V, RL = 32 Ω, AV = 0 dB 50 I DD – Supply Current – mA 50 I DD – Supply Current – mA 60 VDD = 5 V, RL = 10 kΩ, AV = 0 dB 40 30 20 10 40 30 20 10 0 0 10 20 30 40 50 60 VO – Output Voltage – mV 70 80 0 0 20 40 60 80 100 120 140 160 180 PO – Output Power – mW Figure 26 Figure 27 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 15 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 APPLICATION INFORMATION eliminating the output filter with the TPA2000D4 This section will focus on why the user can eliminate the output filter with the TPA2000D4. effect on audio The class-D amplifier outputs a pulse-width modulated (PWM) square wave, which is the sum of the switching waveform and the amplified input audio signal. The human ear acts as a band-pass filter such that only the frequencies between approximately 20 Hz and 20 kHz are passed. The switching frequency components are much greater than 20 kHz, so the only signal heard is the amplified input audio signal. traditional class-D modulation scheme The traditional class-D modulation scheme, which is used in the TPA005Dxx family, has a differential output where each output is 180 degrees out of phase and changes from ground to the supply voltage, VDD. Therefore, the differential prefiltered output varies between positive and negative VDD, where filtered 50% duty cycle yields 0 V across the load. The traditional class-D modulation scheme with voltage and current waveforms is shown in Figure 28. Note that even at an average of 0 V across the load (50% duty cycle), the current to the load is high thus, causing a high supply current. OUT+ OUT– 5V Differential Voltage Across Load OV –5 V Current Figure 28. Traditional Class-D Modulation Scheme’s Output Voltage and Current Waveforms Into an Inductive Load With No Input TPA2000D4 modulation scheme The TPA2000D4 uses a modulation scheme that still has each output switching from 0 to the supply voltage. However, OUT+ and OUT– are now in phase with each other with no input. The duty cycle of OUT+ is greater than 50% and OUT– is less than 50% for positive voltages. The duty cycle of OUT+ is less than 50% and OUT– is greater than 50% for negative voltages. The voltage across the load sits at 0 V throughout most of the switching period greatly reducing the switching current, which reduces any I2R losses in the load. 16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 APPLICATION INFORMATION OUT+ OUT– Differential Voltage Across Load Output = 0 V 5V 0V –5 V Current OUT+ OUT– Differential Voltage Output > 0 V 5V 0V Across Load –5 V Current Figure 29. The TPA2000D4 Output Voltage and Current Waveforms Into an Inductive Load efficiency: why you must use a filter with the traditional class-D modulation scheme The main reason that the traditional class-D amplifier needs an output filter is that the switching waveform results in maximum current flow. This causes more loss in the load, which causes lower efficiency. The ripple current is large for the traditional modulation scheme because the ripple current is proportional to voltage multiplied by the time at that voltage. The differential voltage swing is 2 × VDD and the time at each voltage is half the period for the traditional modulation scheme. An ideal LC filter is needed to store the ripple current from each half cycle for the next half cycle, while any resistance causes power dissipation. The speaker is both resistive and reactive, whereas an LC filter is almost purely reactive. The TPA2000D4 modulation scheme has very little loss in the load without a filter because the pulses are very short and the change in voltage is VDD instead of 2 × VDD. As the output power increases, the pulses widen making the ripple current larger. Ripple current could be filtered with an LC filter for increased efficiency, but for most applications the filter is not needed. An LC filter with a cut-off frequency less than the class-D switching frequency allows the switching current to flow through the filter instead of the load. The filter has less resistance than the speaker that results in less power dissipated, which increases efficiency. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 17 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 APPLICATION INFORMATION effects of applying a square wave into a speaker Audio specialists have said for years not to apply a square wave to speakers. If the amplitude of the waveform is high enough and the frequency of the square wave is within the bandwidth of the speaker, the square wave could cause the voice coil to jump out of the air gap and/or scar the voice coil. A 250-kHz switching frequency, however, is not significant because the speaker cone movement is proportional to 1/f2 for frequencies beyond the audio band. Therefore, the amount of cone movement at the switching frequency is very small. However, damage could occur to the speaker if the voice coil is not designed to handle the additional power. To size the speaker for added power, the ripple current dissipated in the load needs to be calculated by subtracting the theoretical supplied power, PSUP THEORETICAL, from the actual supply power, PSUP, at maximum output power, POUT. The switching power dissipated in the speaker is the inverse of the measured efficiency, ηMEASURED, minus the theoretical efficiency, ηTHEORETICAL. PSPKR = PSUP – PSUP THEORETICAL (at max output power) (1) PSPKR = PSUP / POUT – PSUP THEORETICAL / POUT (at max output power) (2) PSPKR = 1/ηMEASURED – 1/ηTHEORETICAL (at max output power) (3) The maximum efficiency of the TPA2000D4 with an 8-Ω load is 85%. Using equation 3 with the efficiency at maximum power from Figure 2 (78%), we see that there is an additional 106 mW dissipated in the speaker. The added power dissipated in the speaker is not an issue as long as it is taken into account when choosing the speaker. when to use an output filter Design the TPA2000D4 without the filter if the traces from amplifier to speaker are short. The TPA2000D4 passed FCC and CE radiated emissions with no shielding with speaker wires 8 inches long or less. Notebook PCs and powered speakers where the speaker is in the same enclosure as the amplifier are good applications for class-D without a filter. A ferrite bead filter can often be used if the design is failing radiated emissions without a filter, and the frequency sensitive circuit is greater than 1 MHz. This is good for circuits that just have to pass FCC and CE because FCC and CE only test radiated emissions greater than 30 MHz. If choosing a ferrite bead, choose one with high impedance at high frequencies, but very low impedance at low frequencies. Use an output filter if there are low frequency (< 1 MHz) EMI sensitive circuits and/or there are long leads from amplifier to speaker. gain setting via GAIN0 and GAIN1 inputs The gain of the TPA2000D4 is set by two input terminals, GAIN0 and GAIN1. The gains listed in Table 1 are realized by changing the taps on the input resistors inside the amplifier. This causes the input impedance, ZI, to be dependent on the gain setting. The actual gain settings are controlled by ratios of resistors, so the actual gain distribution from part-to-part is quite good. However, the input impedance may shift by 30% due to shifts in the actual resistance of the input resistors. For design purposes, the input network (discussed in the next section) should be designed assuming an input impedance of 20 kΩ, which is the absolute minimum input impedance of the TPA2000D4. At the higher gain settings, the input impedance could increase as high as 115 kΩ. 18 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 APPLICATION INFORMATION Table 1. Gain Settings AMPLIFIER GAIN (dB) INPUT IMPEDANCE (kΩ) TYP TYP 8 104 1 12 74 1 0 17.5 44 1 1 23.5 24 GAIN0 GAIN1 0 0 0 input resistance Each gain setting is achieved by varying the input resistance of the amplifier, which can range from its smallest value to over 6 times that value. As a result, if a single capacitor is used in the input high pass filter, the –3 dB or cut-off frequency will also change by over 6 times. If an additional resistor is connected from the input pin of the amplifier to ground, as shown in the figure below, the variation of the cut-off frequency will be much reduced. ZF CI IN Input Signal ZI R The –3 dB frequency can be calculated using equation 4: f –3 dB 1 2 C IR Z I (4) If the filter must be more accurate, the value of the capacitor should be increased while value of the resistor to ground should be decreased. In addition, the order of the filter could be increased. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 19 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 APPLICATION INFORMATION input capacitor, CI In the typical application an input capacitor, CI, is required to allow the amplifier to bias the input signal to the proper dc level for optimum operation. In this case, CI and the input impedance of the amplifier, ZI, form a high-pass filter with the corner frequency determined in equation 5. –3 dB f c(highpass) (5) 1 2 ZI CI fc The value of CI is important as it directly affects the bass (low frequency) performance of the circuit. Consider the example where ZI is 20 kΩ and the specification calls for a flat bass response down to 80 Hz. Equation 5 is reconfigured as equation 6. CI 1 2 Z I f c (6) In this example, CI is 0.1 µF so one would likely choose a value in the range of 0.1 µF to 1 µF. If the gain is known and will be constant, use ZI from Table 1 to calculate CI. A further consideration for this capacitor is the leakage path from the input source through the input network (CI) and the feedback network to the load. This leakage current creates a dc offset voltage at the input to the amplifier that reduces useful headroom, especially in high gain applications. For this reason a low-leakage tantalum or ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the capacitor should face the amplifier input in most applications as the dc level there is held at VDD/2, which is likely higher than the source dc level. Note that it is important to confirm the capacitor polarity in the application. CI must be 10 times smaller than the bypass capacitor to reduce clicking and popping noise from power on/off and entering and leaving shutdown. After sizing CI for a given cut-off frequency, size the bypass capacitor to 10 times that of the input capacitor. CI ≤ CBYP / 10 20 (7) POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 APPLICATION INFORMATION gain setting resistors, RF and RI for HP amplifier The voltage gain for the TPA2000D4 headphone amplifier is set by resistors RF and RI according to equation 8. Gain RF RI or Gain (dB) 20 log RF RI (8) Given that the TPA2000D4 is a MOS amplifier, the input impedance is very high. Consequently input leakage currents are not generally a concern, although noise in the circuit increases as the value of RF increases. In addition, a certain range of RF values is required for proper start-up operation of the amplifier. Taken together it is recommended that the effective impedance seen by the inverting node of the amplifier be set between 5 kΩ and 20 kΩ. The effective impedance is calculated in equation 9. Effective Impedance R FR I (9) RF RI As an example, consider an input resistance of 20 kΩ and a feedback resistor of 20 kΩ. The gain of the amplifier would be – 1 and the effective impedance at the inverting terminal would be 10 kΩ, which is within the recommended range. For high performance applications, metal film resistors are recommended because they tend to have lower noise levels than carbon resistors. For values of RF above 50 kΩ, the amplifier tends to become unstable due to a pole formed from RF and the inherent input capacitance of the MOS input structure. For this reason, a small compensation capacitor of approximately 5 pF should be placed in parallel with RF. This, in effect, creates a low-pass filter network with the cutoff frequency defined in equation 10. fc 1 2 R F C F (10) For example, if RF is 100 kΩ and CF is 5 pF then fc is 318 kHz, which is well outside the audio range. For maximum signal swing and output power at low supply voltages like 1.6 V to 3.3 V, BYPASS is biased to VDD/4. However, to allow the output to be biased at VDD/2, a resistor, R, equal to RF must be placed from the negative input to ground. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 21 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 APPLICATION INFORMATION input capacitor, CI for HP amplifier In the typical application, an input capacitor, CI, is required to allow the amplifier to bias the input signal to the proper dc level for optimum operation. In this case, CI and RI form a high-pass filter with the corner frequency determined in equation 11. fc 1 2 R I C I (11) The value of CI is important to consider, as it directly affects the bass (low frequency) performance of the circuit. Consider the example where RI is 20 kΩ and the specification calls for a flat bass response down to 20 Hz. Equation 4 is reconfigured as equation 12. CI 1 2 R I f c (12) In this example, CI is 0.40 µF, so one would likely choose a value in the range of 0.47 µF to 1 µF. A further consideration for this capacitor is the leakage path from the input source through the input network (RI, CI) and the feedback resistor (RF) to the load. This leakage current creates a dc offset voltage at the input to the amplifier that reduces useful headroom, especially in high-gain applications (>10). For this reason a low-leakage tantalum or ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the capacitor should face the amplifier input in most applications, as the dc level there is held at VDD/4, which is likely higher than the source dc level. It is important to confirm the capacitor polarity in the application. output coupling capacitor, CC for HP amplifier In the typical single-supply single-ended (SE) configuration, an output coupling capacitor (CC) is required to block the dc bias at the output of the amplifier, thus preventing dc currents in the load. As with the input coupling capacitor, the output coupling capacitor and impedance of the load form a high-pass filter governed by equation 13. fc 1 2 R L C C (13) The main disadvantage, from a performance standpoint, is that the typically small load impedances drive the low-frequency corner higher. Large values of CC are required to pass low frequencies into the load. Consider the example where a CC of 68 µF is chosen and loads vary from 32 Ω to 47 kΩ. Table 2 summarizes the frequency response characteristics of each configuration. Table 2. Common Load Impedances vs Low Frequency Output Characteristics in SE Mode RL CC Lowest Frequency 32 Ω 68 µF 73 Hz 10,000 Ω 68 µF 0.23 Hz 47,000 Ω 68 µF 0.05 Hz As Table 2 indicates, headphone response is adequate and drive into line level inputs (a home stereo for example) is very good. 22 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 APPLICATION INFORMATION output coupling capacitor, CC (continued) The output coupling capacitor required in single-supply SE mode also places additional constraints on the selection of other components in the amplifier circuit. With the rules described earlier still valid, add the following relationship: 1 CB 55 kΩ 1 CI RI 1 R LC C (14) power supply decoupling, CS The TPA2000D4 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output total harmonic distortion (THD) is as low as possible. Power supply decoupling also prevents oscillations for long lead lengths between the amplifier and the speaker. The optimum decoupling is achieved by using two capacitors of different types that target different types of noise on the power supply leads. For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resistance (ESR) ceramic capacitor, typically 0.1 µF, placed as close as possible to the device VDD lead works best. For filtering lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10 µF or greater, placed near the audio power amplifier is recommended. midrail bypass capacitor, CBYP The midrail bypass capacitor, CBYP, is the most critical capacitor and serves several important functions. During start-up or recovery from shutdown mode, CBYP determines the rate at which the amplifier starts up. The second function is to reduce noise produced by the power supply caused by coupling into the output drive signal. This noise is from the midrail generation circuit internal to the amplifier, which appears as degraded PSRR and THD+N. Bypass capacitor (CBYP) values of 0.47-µF to 1-µF ceramic or tantalum, low-ESR capacitors are recommended for the best THD and noise performance. Increasing the bypass capacitor reduces clicking and popping noise from power on/off and entering and leaving shutdown. To have minimal pop, CBYP should be 10 times larger than CI. CBYP ≥ 10 × CI (15) differential input The differential input stage of the amplifier cancels any noise that appears on both input lines of a channel. To use the TPA2000D4 EVM with a differential source, connect the positive lead of the audio source to the RINP (LINP) input and the negative lead from the audio source to the RINN (LINN) input. To use the TPA2000D4 with a single-ended source, ac ground the RINN and LINN inputs through a capacitor and apply the audio single to the RINP and LINP inputs. In a single-ended input application, the RINN and LINN inputs should be ac grounded at the audio source instead of at the device inputs for best noise performance. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 23 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 APPLICATION INFORMATION shutdown modes The TPA2000D4 employs a shutdown mode of operation designed to reduce supply current, IDD, to the absolute minimum level during periods of nonuse for battery-power conservation. The SHUTDOWN input terminal should be held high during normal operation when the amplifier is in use. Pulling SHUTDOWN low causes the outputs to mute and the amplifier to enter a low-current state, IDD(SD) = 0.05 µA. SHUTDOWN should never be left unconnected because amplifier operation would be unpredictable. using low-ESR capacitors Low-ESR capacitors are recommended throughout this application section. A real (as opposed to ideal) capacitor can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this resistor minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this resistance the more the real capacitor behaves like an ideal capacitor. 24 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 MECHANICAL DATA DAP (R-PDSO-G**) PowerPAD PLASTIC SMALL-OUTLINE PACKAGE 38 PINS SHOWN 0,30 0,19 0,65 38 0,13 M 20 Thermal Pad (see Note D) 6,20 NOM 8,40 7,80 0,15 NOM Gage Plane 1 19 0,25 A 0°–8° 0,75 0,50 Seating Plane 0,15 0,05 1,20 MAX PINS ** 0,10 28 30 32 38 A MAX 9,80 11,10 11,10 12,60 A MIN 9,60 10,90 10,90 12,40 DIM 4073257/A 07/97 NOTES: A. B. C. D. All linear dimensions are in millimeters. This drawing is subject to change without notice. Body dimensions do not include mold flash or protrusion. The package thermal performance may be enhanced by bonding the thermal pad to an external thermal plane. This pad is electrically and thermally connected to the backside of the die and possibly selected leads. E. Falls within JEDEC MO-153 PowerPAD is a trademark of Texas Instruments. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 25 TPA2000D4 STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER WITH STEREO HP AMPLIFIER SLOS337 – DECEMBER 2000 MECHANICAL DATA GQC (S-PBGA-N48) PLASTIC BALL GRID ARRAY 4,10 3,90 SQ 3,00 TYP 0,50 0,50 G F E D C B A 1 2 3 4 5 6 7 0,68 0,62 1,00 MAX Seating Plane 0,35 0,25 0,05 M 0,21 0,08 0,11 4200460/C 10/00 NOTES: A. B. C. D. All linear dimensions are in millimeters. This drawing is subject to change without notice. MicroStar Junior BGA configuration Falls within JEDEC MO-225 MicroStar Junior BGA is a trademark of Texas Instruments. 26 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. Customers are responsible for their applications using TI components. In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. TI’s publication of information regarding any third party’s products or services does not constitute TI’s approval, warranty or endorsement thereof. Copyright 2000, Texas Instruments Incorporated