TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 DCA PACKAGE (TOP VIEW) NOT RECOMMENDED FOR NEW DESIGNS D D D D D D D D D D Choose TPA2000D2 For Upgrade Extremely Efficient Class-D Stereo Operation Drives L and R Channels 2-W BTL Output into 4 Ω 5-W Peak Music Power Fully Specified for 5-V Operation Low Quiescent Current Shutdown Control Thermally-Enhanced PowerPAD SurfaceMount Packaging Thermal and Under-Voltage Protection description The TPA005D02 is a monolithic power IC stereo audio amplifier. It operates in extremely efficient Class-D operation, using the high switching speed of power DMOS transistors. These transistors replicate the analog signal through high-frequency switching of the output stage. This allows the TPA005D02 to be configured as a bridge-tied load (BTL) amplifier. When configured as a BTL amplifier, the TPA005D02 is capable of delivering up to 2 W of continuous average power into a 4-Ω load at 0.5% THD+N from a 5-V power supply in the high fidelity range (20 Hz to 20 kHz). SHUTDOWN MUTE AGND LINN LINP LCOMP AGND VDD LPVDD LOUTP LOUTP PGND PGND LOUTN LOUTN LPVDD NC NC NC AGND PVDD VCP CP3 CP2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 COSC AGND AGND RINN RINP RCOMP FAULT0 FAULT1 RPVDD ROUTP ROUTP PGND PGND ROUTN ROUTN RPVDD PVDD NC NC V2P5 LSBIAS PGND CP4 CP1 NC – No internal connection A BTL configuration eliminates the need for external coupling capacitors on the output. A chip-level shutdown control limits total supply current to 400 µA. This makes the device ideal for battery-powered applications. Protection circuitry increases device reliability: thermal and under-voltage shutdown, with two status feedback terminals for use when any error condition is encountered. The high switching frequency of the TPA005D02 allows the output filter to consist of three small capacitors and two small inductors per channel. The high switching frequency also allows for good THD+N performance. The TPA005D02 is offered in the thermally enhanced 48-pin PowerPAD TSSOP surface-mount package (designator DCA). 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. PowerPAD is a trademark of Texas Instruments Incorporated. Copyright 2000, Texas Instruments Incorporated PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1 LPVDD POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 PVDD GATE DRIVE VDD BIAS GENERATOR HPVCC V2P5 COSC VCP LSBIAS RAMP GENERATOR _ RCOMP VCP-UVLO DETECT GATE DRIVE + PVDD + _ RINP RINN 10 kΩ 10 kΩ 1.5 V RPVDD AGND RPVDD RPVDD RPVDD TRIPLER CHARGE PUMP GATE DRIVE CP1 CP2 NOTE A: LPVDD, RPVDD, VDD, and PVDD are externally connected. AGND and PGND are externally connected. CP3 CP4 VCP PVDD ROUTN ROUTP PGND VCP LSBIAS Template Release Date: 7–11–94 + _ LCOMP MUTE TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER VCP LSBIAS SHUTDOWN CONTROL and STARTUP LOGIC SLOS227C – AUGUST 1998 – REVISED MARCH 2000 LINN FAULT1 THERMAL DETECT + _ LINP VDD LSBIAS GATE DRIVE 10 kΩ FAULT0 LPVDD 1.5 V 10 kΩ LSBIAS VCP LSBIAS LPVDD LOUTN LOUTP 2 LPVDD TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 Terminal Functions TERMINAL NAME DESCRIPTION NO. AGND 3, 7, 20, 46, 47 COSC 48 Capacitor I/O for ramp generator. Adjust the capacitor size to change the switching frequency. CP1 25 First diode node for charge pump CP2 24 First inverter switching node for charge pump CP3 23 Second diode node for charge pump CP4 26 Second inverter switching node for charge pump FAULT0 42 Logic level fault0 output signal. Lower order bit of the two fault signals with open drain output. FAULT1 41 Logic level fault1 output signal. Higher order bit of the two fault signals with open drain output. LCOMP 6 Compensation capacitor terminal for left-channel Class-D amplifier LINN 4 Class-D left-channel negative input 5 Class-D left-channel positive input LINP Analog ground for analog sections LOUTN 14, 15 Class-D amplifier left-channel negative output of H-bridge LOUTP 10, 11 Class-D amplifier left-channel positive output of H-bridge LPVDD LSBIAS 9, 16 Class-D amplifier left-channel power supply 28 Level-shifter power supply, to be tied to VCP 2 Active-low logic-level mute input signal. When MUTE is held low, the selected amplifier is muted. When MUTE is held high, the device operates normally. When the Class-D amplifier is muted, the low-side output transistors are turned on, shorting the load to ground. MUTE NC PGND 17, 18, 19, 30, 31 12, 13 No internal connection Power ground for left-channel H–bridge only PGND 27 PGND 36, 37 Power ground for right-channel H-bridge only PVDD RCOMP 21, 32 43 VDD supply for charge-pump and internal logic circuitry Compensation capacitor terminal for right-channel Class-D amplifier 45 Class-D right-channel negative input 44 Class-D right-channel positive input RINN RINP Power ground for charge pump only RPVDD ROUTN 33, 40 Class-D amplifier right-channel power supply 34, 35 Class-D amplifier right-channel negative output of H-bridge ROUTP 38, 39 Class-D amplifier right-channel positive output of H-bridge SHUTDOWN 1 Active-low logic-level shutdown input signal. When SHUTDOWN is held low, the device goes into shutdown mode. When SHUTDOWN is held at logic high, the device operates normally. V2P5 29 2.5-V internal reference bypass VCP 22 Storage capacitor terminal for charge pump VDD 8 VDD bias supply for analog circuitry. This terminal needs to be well filtered to prevent degrading the device performance. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 3 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 Class-D amplifier faults Table 1. Amplifier Fault Table FAULT 0† FAULT 1† 1 1 No fault—The device is operating normally. 1 0 Charge pump under-voltage lock-out (VCP-UV) fault—All low-side transistors are turned on, shorting the load to ground. Once the charge pump voltage is restored, normal operation resumes, but FAULT1 is still active. FAULT1 is cleared by cycling MUTE, SHUTDOWN, or the power supply. 0 0 Thermal fault—All the low-side transistors are turned on, shorting the load to ground. Once the junction temperature drops 20°C, normal operation resumes. But the FAULTx terminals are still set and are cleared by cycling MUTE, SHUTDOWN, or the power supply. DESCRIPTION † These logic levels assume a pull up to PVDD from the open-drain outputs. AVAILABLE OPTIONS TA PACKAGED DEVICES TSSOP† (DCA) – 40°C to 125°C TPA005D02DCA † The DCA package is available in left-ended tape and reel. To order a taped and reeled part, add the suffix R to the part number (e.g., TPA005D02DCAR). absolute maximum ratings over operating free-air temperature range, TC = 25°C (unless otherwise noted)‡ Supply voltage, VDD (PVDD, LPVDD, RPVDD, VDD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 V Bias voltage (LSBIAS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 V to 20 V Input voltage, VI (SHUTDOWN, MUTE, MODE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 0.3 V to 5.8 V Output current, IO (FAULT0, FAULT1), open drain terminated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 mA Charge pump voltage, VCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PVDD + 20 V Continuous H-bridge output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 A Pulsed H-Bridge output current, each output, Imax (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 A Continuous total power dissipation, TC = 25°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 W§ Operating virtual junction temperature range, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 40°C to 150°C Operating case temperature range, TC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 40°C to 125°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. § Thermal shutdown activates when TJ = 125°C. NOTE 1: Pulse duration = 10 ms, duty cycle 2% v 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 TA = 125°C POWER RATING DCA 5.6 W 44.8 mW/°C 3.6 W 2.9 W 1.1 W ¶ Please see the Texas Instruments document, PowerPAD Thermally Enhanced Package Application Report (literature number SLMA002), for more information on the PowerPAD package. The thermal data was measured on a PCB layout based on the information in the section entitled Texas Instruments Recommended Board for PowerPAD on page 33 of the before mentioned document. 4 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 recommended operating conditions MIN Supply voltage, PVDD, LPVDD, RPVDD, VDD NOM 4.5 High-level input voltage, VIH MAX 5.5 4.25 V V Low-level input voltage, VIL 0.75 Audio inputs, LINN, LINP, RINN, RINP, HPLIN, HPRIN, differential input voltage 1 PWM frequency UNIT 100 500 V VRMS kHZ electrical characteristics, VDD = PVDD = LPVDD = RPVDD = 5 V, RL = 4 Ω, TC = 25°C, See Figure 1 (resistive load) (unless otherwise noted) PARAMETER TEST CONDITIONS PSRR Power supply rejection ratio IDD IDD(MUTE) Supply current VDD = PVDD = LPVDD = RPVDD = 4.9 V to 5.1 V No load or output filter Supply current, mute mode MUTE = 0 V IDD(SD) IIH Supply current, shutdown mode SHUTDOWN = 0 V High-level input current IIL Low-level input current VIH = 5.3 V VIL = – 0.3 V rDS(on) Total static drain-to-source on-state resistance (low-side plus high-side FETs) rDS(on) Matching MIN TYP MAX 40 25 ID = 0.5 A dB 40 mA 10 15 mA 400 2000 µA 620 95% UNIT 10 µA –10 µA 750 mΩ 99.5% operating characteristics, VDD = PVDD = LPVDD = RPVDD = 5 V, RL = 4 Ω, TC = 25°C, See Figure 1 (unless otherwise noted) PARAMETER PO THD+N TEST CONDITIONS Total harmonic distortion plus noise MAX UNIT W 0.2% 80% Gain 24 Left/right channel gain matching dB 95% Noise floor Dynamic range Crosstalk f = 1 kHz Frequency response bandwidth, post output filter, – 3 dB BOM TYP 2 PO = 1 W, f = 1 kHz RL = 8 Ω Efficiency AV MIN RMS output power, THD = 0.5%, per channel 60 dB 70 dB 55 dB 20 Maximum output power bandwidth 20,000 Hz 20 kHz thermal resistance PARAMETER RθJP TEST CONDITIONS Thermal resistance, junction-to-pad MIN TYP MAX UNIT 10 °C/W RθJA Thermal resistance, junction-to-pad† 22.3 °C/W † Please see the Texas Instruments document, PowerPAD Thermally Enhanced Package Application Report (literature number SLMA002), for more information on the PowerPAD package. The thermal data was measured on a PCB layout based on the information in the section entitled Texas Instruments Recommended Board for PowerPAD on page 33 of the before mentioned document. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 PARAMETER MEASUREMENT INFORMATION FAULT0 VCP PVDD PVDD 28 1 2 FAULT1 LSBIAS SHUTDOWN LOUTN MUTE 42 41 14,15 15 µH 0.22 µF 5V 9,16 LOUTP 1 µF 5 Balanced Differential Input Signal 4 1 µF 43 470 pF LINN 1 µF 4Ω 10,11 15 µH 29 LCOMP 1 µF RCOMP 470 pF VDD 48 4Ω LINP V2P5 6 1 µF 0.22 µF LPVDD 8 COSC 470 pF CP1 1 µF 44 Balanced Differential Input Signal 45 47 nF CP2 RINP CP3 RINN 12,13,27,36,37 5V 21, 32 24 23 47 nF 1 µF 33,40 5V 2, 3, 7,20,46,47 25 CP4 RPVDD AGND (see Note A) VCP 26 22 2.2 µF PGND (see Note A) PVDD ROUTN 34,35 15 µH 0.22 µF 0.22 µF ROUTP Figure 1. 5-V, 4-Ω Test Circuit 6 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 38,39 15 µH TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS Table of Graphs FIGURE IDD vs Switching frequency Supply current THD+N 2 vs Free-air temperature Total harmonic distortion plus noise 3 vs Frequency 4, 5 vs Output power 6, 7 Voltage amplification and phase shift vs Frequency 8 Crosstalk vs Frequency 9 Efficiency vs Output power 10 SUPPLY CURRENT vs FREE–AIR TEMPERATURE SUPPLY CURRENT vs SWITCHING FREQUENCY 50 100 Open Load 80 IDD – Supply Current – mA IDD – Supply Current – mA Open Load 60 With Output Filter 40 40 With Output Filter 30 20 Without Output Filter 10 20 Without Output Filter 0 0 100 200 300 400 500 0 –40 0 40 80 120 125 TA – Free–Air Temperature – °C f – Switching Frequency – Hz Figure 3 Figure 2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 7 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS 1 RL = 4 Ω 0.5 PO = 2W 0.2 0.1 PO = 100 mW PO = 1W 0.05 0.02 0.01 20 100 200 50 500 1k 2k TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY THD+N – Total Harmonic Distortion Plus Noise – % THD+N – Total Harmonic Distortion Plus Noise – % TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY 5k 10k 20k 1 RL = 8 Ω 0.5 PO = 100 mW 0.2 0.1 PO = 1W 0.05 0.02 0.01 20 50 100 200 f – Frequency – Hz THD+N – Total Harmonic Distortion Plus Noise – % THD+N – Total Harmonic Distortion Plus Noise – % RL = 4 Ω 2 1 0.5 f = 1 kHz 0.2 0.1 f = 20 kHz f = 20 Hz 0.05 f = 20 kHz f = 20 Hz 0.02 0.01 0.01 0.02 0.05 0.1 0.2 5k 10k 20k 0.5 1 2 5 10 10 5 TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER RL = 8 Ω 2 1 0.5 0.2 f = 1 kHz f = 20 Hz 0.1 0.05 f = 20 kHz 0.02 0.01 10m 20m 50m 100m 200m 500m 1 PO – Output Power – W Figure 7 POST OFFICE BOX 655303 2 PO – Output Power – W Figure 6 8 2k Figure 5 TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER 5 500 1k f – Frequency – Hz Figure 4 10 PO = 500 mW • DALLAS, TEXAS 75265 5 10 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS GAIN AND PHASE vs FREQUENCY 28 Voltage Amplification 26 24 22 20 Gain – dB 18 Phase Shift 16 14 12 10 8 6 4 2 0 10 20 50 100 200 500 1k 2k 45° 40° 35° 30° 25° 20° 15° 10° 5° 0° – 5° – 10° – 15° – 20° – 25° – 30° – 35° – 40° – 45° 5k 10k 20k 50k 100k Po = 2W RL = 4Ω Phase 30 f – Frequency – Hz Figure 8 CROSSTALK vs FREQUENCY EFFICIENCY vs OUTPUT POWER 0 90 PO = 2W RL = 4Ω –10 –20 RL = 8Ω –30 80 –50 –60 –70 Efficiency – % Crosstalk – dB –40 Left-to-Right –80 –90 –100 –110 RL = 4Ω 70 60 Right-to-Left –120 –130 50 –140 –150 20 50 100 200 500 1k 2k 5k 10k 20k 40 0 0.4 0.8 1.2 1.6 2.0 PO – Output Power – W f – Frequency – Hz Figure 10 Figure 9 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 9 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 THERMAL INFORMATION The thermally enhanced DCA package is based on the 56-pin TSSOP, but includes a thermal pad (see Figure 11) to provide an effective thermal contact between the IC and the PWB. Traditionally, surface mount and power have been mutually exclusive terms. A variety of scaled-down TO-220-type packages have leads formed as gull wings to make them applicable for surface-mount applications. These packages, however, have only two shortcomings: they do not address the very low profile requirements (< 2 mm) of many of today’s advanced systems, and they do not offer a terminal-count high enough to accommodate increasing integration. On the other hand, traditional low-power surface-mount packages require power-dissipation derating that severely limits the usable range of many high-performance analog circuits. The PowerPAD package (thermally enhanced TSSOP) combines fine-pitch surface-mount technology with thermal performance comparable to much larger power packages. The PowerPAD package is designed to optimize the heat transfer to the PWB. Because of the very small size and limited mass of a TSSOP package, thermal enhancement is achieved by improving the thermal conduction paths that remove heat from the component. The thermal pad is formed using a patented lead-frame design and manufacturing technique to provide a direct connection to the heat-generating IC. When this pad is soldered or otherwise thermally coupled to an external heat dissipator, high power dissipation in the ultra-thin, fine-pitch, surface-mount package can be reliably achieved. DIE Side View (a) Thermal Pad DIE End View (b) Bottom View (c) Figure 11. Views of Thermally Enhanced DCA Package selection of components Figure 12 is a schematic diagram of a typical notebook computer application circuit. 10 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 APPLICATION INFORMATION FAULT0 VCP PVDD PVDD 28 1 2 FAULT1 LSBIAS SHUTDOWN LOUTN MUTE 42 41 14,15 15 µH 0.22 µF 5V 9,16 LOUTP 1 µF 5 Balanced Differential Input Signal 4 1 µF 43 470 pF LINN 1 µF 4Ω 10,11 15 µH 29 LCOMP 1 µF RCOMP 470 pF VDD 48 4Ω LINP V2P5 6 1 µF 0.22 µF LPVDD 8 COSC 470 pF CP1 1 µF 44 Balanced Differential Input Signal 45 47 nF CP2 RINP CP3 RINN 12,13,27,36,37 5V 21, 32 24 23 47 nF 1 µF 33,40 5V 2, 3, 7,20,46,47 25 CP4 RPVDD AGND (see Note A) VCP 26 22 2.2 µF PGND (see Note A) PVDD ROUTN 34,35 15 µH 0.22 µF 0.22 µF ROUTP 38,39 15 µH NOTE A: A 0.1 µF ceramic capacitor should be placed as close as possible to the IC. For filtering lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10 µF or greater should be placed near the audio power amplifier. Figure 12. TPA005D02 Typical Configuration Application Circuit POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 11 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 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 RIN, the TPA005D002’s input resistance forms a high-pass filter with the corner frequency determined in equation 8. –3 dB f c(highpass) + 2 p R1 (8) C IN I RIN is nominally 10 kΩ fc The value of CI is important to consider as it directly affects the bass (low frequency) performance of the circuit. Consider the example where the specification calls for a flat bass response down to 40 Hz. Equation 8 is reconfigured as equation 9. CI + 2 p R1 (9) f IN c 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 low-leakage tantalum or ceramic capacitor is the best choice for the input capacitors. When polarized capacitors are used, the positive side of the capacitor should face the amplifier input as the dc level there is held at 1.5 V, which is likely higher than the source dc level. Please note that it is important to confirm the capacitor polarity in the application. differential input The TPA005D02 has differential inputs to minimize distortion at the input to the IC. Since these inputs nominally sit at 1.5 V, dc-blocking capacitors are required on each of the four input terminals. If the signal source is single-ended, optimal performance is achieved by treating the signal ground as a signal. In other words, reference the signal ground at the signal source, and run a trace to the dc-blocking capacitor which should be located physically close to the TPA005D02. If this is not feasible, it is still necessary to locally ground the unused input terminal through a dc-blocking capacitor. power supply decoupling, CS The TPA005D02 is a high-performance Class-D 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-seriesresistance (ESR) ceramic capacitor, typically 0.1 µF placed as close as possible to the device’s various VDD leads 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. The TPA005D02 has several different power supply terminals. This was done to isolate the noise resulting from high-current switching from the sensitive analog circuitry inside the IC. 12 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 APPLICATION INFORMATION mute and shutdown modes The TPA005D02 employs both a mute and 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 = 400 µA. Mute mode alone reduces IDD to 10 mA. Table 2. Shutdown and Mute Mode Functions INPUTS† OUTPUT SE/BTL HP/LINE MUTE IN Low Low X X X X Low High High High AMPLIFIER STATE SHUTDOWN MUTE OUT INPUT Low Low Low L/R Line BTL — High — X Mute High — High X Mute Low Low Low L/R HP BTL Low Low Low Low L/R Line SE High Low Low Low L/R HP SE OUTPUT † Inputs should never be left unconnected. X = do not care using low-ESR capacitors Low-ESR capacitors are recommended throughout this applications 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. output filter components The output inductors are key elements in the performance of the class D audio amplifier system. It is important that these inductors have a high enough current rating and a relatively constant inductance over frequency and temperature. The current rating should be higher than the expected maximum current to avoid magnetically saturating the inductor. When saturation occurs, the inductor loses its functionality and looks like a short circuit to the PWM signal, which increases the harmonic distortion considerably. A shielded inductor may be required if the class D amplifier is placed in an EMI sensitive system; however, the switching frequency is low for EMI considerations and should not be an issue in most systems. The DC series resistance of the inductor should be low to minimize losses due to power dissipation in the inductor, which reduces the efficiency of the circuit. Capacitors are important in attenuating the switching frequency and high frequency noise, and in supplying some of the current to the load. It is best to use capacitors with low equivalent-series-resistance (ESR). A low ESR means that less power is dissipated in the capacitor as it shunts the high-frequency signals. Placing these capacitors in parallel also parallels their ESR, effectively reducing the overall ESR value. The voltage rating is also important, and, as a rule of thumb, should be 2 to 3 times the maximum rms voltage expected to allow for high peak voltages and transient spikes. These output filter capacitors should be stable over temperature since large currents flow through them. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 13 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 APPLICATION INFORMATION efficiency of class D vs linear operation Amplifier efficiency is defined as the ratio of output power delivered to the load to power drawn from the supply. In the efficiency equation below, PL is power across the load and PSUP is the supply power. Efficiency + h + PP L SUP A high-efficiency amplifier has a number of advantages over one with lower efficiency. One of these advantages is a lower power requirement for a given output, which translates into less waste heat that must be removed from the device, smaller power supply required, and increased battery life. Audio power amplifier systems have traditionally used linear amplifiers, which are well known for being inefficient. Class D amplifiers were developed as a means to increase the efficiency of audio power amplifier systems. A linear amplifier is designed to act as a variable resistor network between the power supply and the load. The transistors operate in their linear region and voltage that is dropped across the transistors (in their role as variable resistors) is lost as heat, particularly in the output transistors. The output transistors of a class D amplifier switch from full OFF to full ON (saturated) and then back again, spending very little time in the linear region in between. As a result, very little power is lost to heat because the transistors are not operated in their linear region. If the transistors have a low ON resistance, little voltage is dropped across them, further reducing losses. The ideal class D amplifier is 100% efficient, which assumes that both the ON resistance (RDS(ON)) and the switching times of the output transistors are zero. the ideal class D amplifier To illustrate how the output transistors of a class D amplifier operate, a half-bridge application is examined first (Figure 13). VDD M1 VA IL IOUT + L M2 RL CL C VOUT – Figure 13. Half-Bridge Class D Output Stage Figures 14 and 15 show the currents and voltages of the half-bridge circuit. When transistor M1 is on and M2 is off, the inductor current is approximately equal to the supply current. When M2 switches on and M1 switches off, the supply current drops to zero, but the inductor keeps the inductor current from dropping. The additional inductor current is flowing through M2 from ground. This means that VA (the voltage at the drain of M2, as shown in Figure 13) transitions between the supply voltage and slightly below ground. The inductor and capacitor form a low-pass filter, which makes the output current equal to the average of the inductor current. The low pass filter averages VA, which makes VOUT equal to the supply voltage multiplied by the duty cycle. 14 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 APPLICATION INFORMATION the ideal class D amplifier (continued) Control logic is used to adjust the output power, and both transistors are never on at the same time. If the output voltage is rising, M1 is on for a longer period of time than M2. Inductor Current Output Current Current Supply Current 0 M1 on M1 off M1 on M2 off M2 on M2 off Time Figure 14. Class D Currents VDD Voltage VA VOUT 0 M1 on M1 off M1 on M2 off M2 on M2 off Time Figure 15. Class D Voltages POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 15 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 APPLICATION INFORMATION the ideal class D amplifier (continued) Given these plots, the efficiency of the class D device can be calculated and compared to an ideal linear amplifier device. In the derivation below, a sine wave of peak voltage (VP) is the output from an ideal class D and linear amplifier and the efficiency is calculated. CLASS D V L(rms) + Ǹ2 V L(rms) ǒ Ǔ+ Average I DD PL LINEAR VP + VL + VDD P SUP + V DD V L(rms) PL V DD IL P SUP Efficiency I L(rms) V L(rms)2 RL +2 R ǒ Ǔ+p ǒ Ǔ P SUP V L(rms) Efficiency V DD L VP 2 + VDD RL ǒ Ǔ+ Average I DD V DD V P RL 2 p + h + PP L SUP + h + PP L Efficiency SUP Efficiency V P2 Average I DD Average I DD I L(rms) + + Ǹ2 VP V P2 2R L + h + VDD V 2 p + h +1 Efficiency + h + p4 V V P RL P DD In the ideal efficiency equations, assume that VP = VDD, which is the maximum sine wave magnitude without clipping. Then, the highest efficiency that a linear amplifier can have without clipping is 78.5%. A class D amplifier, however, can ideally have an efficiency of 100% at all power levels. The derivation above applies to an H-bridge as well as a half-bridge. An H-bridge requires approximately twice the supply current but only requires half the supply voltage to achieve the same output power—factors that cancel in the efficiency calculation. The H-bridge circuit is shown in Figure 16. VDD M1 VA VDD IL IOUT M4 + VOUT – L M2 L RL CL CL Figure 16. H-Bridge Class D Output Stage 16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 M3 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 APPLICATION INFORMATION losses in a real-world class D amplifier Losses make class D amplifiers nonideal, and reduce the efficiency below 100%. These losses are due to the output transistors having a nonzero RDS(on), and rise and fall times that are greater than zero. The loss due to a nonzero RDS(on) is called conduction loss, and is the power lost in the output transistors at nonswitching times, when the transistor is ON (saturated). Any RDS(on) above 0 Ω causes conduction loss. Figure 17 shows an H-bridge output circuit simplified for conduction loss analysis and can be used to determine new efficiencies with conduction losses included. VDD = 5 V RDS(on) 0.31 Ω 5 MΩ RDS(off) 0.31 Ω RDS(on) RL 4Ω RDS(off) 5 MΩ Figure 17. Output Transistor Simplification for Conduction Loss Calculation The power supplied, PSUP, is determined to be the power output to the load plus the power lost in the transistors, assuming that there are always two transistors on. Efficiency + h + PP L SUP Efficiency Efficiency + h + I2 2R + h + 2R DS(on) RL ǒ ǒ DS(on) + h + 95% Efficiency + h + 87% Efficiency I 2R L ) I2RL ) RL Ǔ + 0.1, RL + 4 at all output levels R DS(on) + 0.31, R L + 4 at all output levels R DS(on) POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 Ǔ 17 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 APPLICATION INFORMATION losses in a real-world class D amplifier (continued) Losses due to rise and fall times are called switching losses. A plot of the output, showing switching losses, is shown in Figure 18. 1 f tSWon SW tSWoff + = tSW Figure 18. Output Switching Losses Rise and fall times are greater than zero for several reasons. One is that the output transistors cannot switch instantaneously because (assuming a MOSFET) the channel from drain to source requires a specific period of time to form. Another is that transistor gate-source capacitance and parasitic resistance in traces form RC time constants that also increase rise and fall times. Switching losses are constant at all output power levels, which means that switching losses can be ignored at high power levels in most cases. At low power levels, however, switching losses must be taken into account when calculating efficiency. Switching losses are dominated by conduction losses at the high output powers, but should be considered at low powers. The switching losses are automatically taken into account if you consider the quiescent current with the output filter and load. class D effect on power supply Efficiency calculations are an important factor for proper power supply design in amplifier systems. Table 2 shows Class D efficiency at a range of output power levels (per channel) with a 1-kHz sine wave input. The maximum power supply draw from a stereo 1-W per channel audio system with 8-Ω loads and a 5-V supply is almost 2.7 W. A similar linear amplifier such as the TPA005D02 has a maximum draw of 3.25 W under the same circumstances. Table 3. Efficiency vs Output Power in 5-V 8-Ω H-Bridge Systems Output Power (W) Efficiency (%) Peak Voltage (V) Internal Dissipation (W) 0.25 63.4 2 0.145 0.5 73 2.83 0.183 0.75 77.1 3.46 0.222 1 79.3 80.6 4 4.47† 0.314 1.25 † High peak voltages cause the THD to increase 18 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 0.3 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 APPLICATION INFORMATION class D effect on power supply (continued) There is a minor power supply savings with a class D amplifier versus a linear amplifier when amplifying sine waves. The difference is much larger when the amplifier is used strictly for music. This is because music has much lower RMS output power levels, given the same peak output power (Figure 19); and although linear devices are relatively efficient at high RMS output levels, they are very inefficient at mid-to-low RMS power levels. The standard method of comparing the peak power to RMS power for a given signal is crest factor, whose equation is shown below. The lower RMS power for a set peak power results in a higher crest factor Crest Factor + 10 log PP PK rms Power PPK PRMS Time Figure 19. Audio Signal Showing Peak and RMS Power Figure 20 is a comparison of a 5-V class D amplifier to a similar linear amplifier playing music that has a 13.76-dB crest factor. From the plot, the power supply draw from a stereo amplifier that is playing music with a 13.76 dB crest factor is 1.02 W, while a class D amplifier draws 420 mW under the same conditions. This means that just under 2.5 times the power supply is required for a linear amplifier over a class D amplifier. POWER SUPPLIED vs PEAK OUTPUT VOLTAGE AND PEAK OUTPUT POWER 600 Power Supplied (mW) 500 400 TPA0202 300 TPA005D02 200 100 0 1 0.25 1.5 0.56 2 1 2.5 1.56 3 2.25 3.5 3.06 4 4 4.5 5.06 Peak Output Voltage (V) Peak Output Power (W) Figure 20. Audio Signal Showing Peak and RMS Power (with Music Applied) POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 19 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 APPLICATION INFORMATION class D effect on battery life Battery operations for class D amplifiers versus linear amplifiers have similar power supply savings results. The essential contributing factor to longer battery life is lower RMS supply current. Figure 21 compares the TPA005D02 supply current to the supply current of the TPA0202, a 2-W linear device, while playing music at different peak voltage levels. SUPPLY CURRENTS vs PEAK OUTPUT VOLTAGE AND PEAK OUTPUT POWER 400 Supply Current (mA rms) 350 300 250 TPA0202 200 150 100 TPA005D02 50 0 1 0.25 1.5 0.56 2 1 2.5 1.56 3 2.25 3.5 3.06 4 4 Peak Output Voltage (V) Peak Output Power (W) Figure 21. Supply Current vs Peak Output Voltage of TPA005D02 vs TPA0202 With Music Input This plot shows that a linear amplifier has approximately three times more current draw at normal listening levels than a class D amplifier. Thus, a class D amplifier has approximately three times longer battery life at normal listening levels. If there is other circuitry in the system drawing supply current, that must also be taken into account when estimating battery life savings. 20 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 APPLICATION INFORMATION crest factor and thermal considerations A typical music CD requires 12 dB to 15 dB of dynamic headroom to pass the loudest portions without distortion as compared with the average power output. From the TPA005D02 data sheet, one can see that when the TPA005D02 is operating from a 5-V supply into a 4-Ω speaker that 4 W peaks are available. Converting Watts to dB: P dB + 10 Log ǒǓ PW P ref + 10Log ǒ Ǔ+ 4 1 6 dB (17) Subtracting the crest factor restriction to obtain the average listening level without distortion yields: * 18 dB + * 12 dB (15 dB crest factor) 6.0 dB * 15 dB + * 9 dB (15 dB crest factor) 6.0 dB * 12 dB + * 6 dB (12 dB crest factor) 6.0 dB * 9 dB + * 3 dB (9 dB crest factor) 6.0 dB * 6 dB + * 0 dB (6 dB crest factor) 6.0 dB * 3 dB + 3 dB (3 dB crest factor) 6.0 dB Converting dB back into watts: PW + 10PdBń10 Pref + 63 mW (18 dB crest factor) + 125 mW (15 dB crest factor) + 250 mW (12 dB crest factor) + 500 mW (9 dB crest factor) + 1000 mW (6 dB crest factor) + 2000 mW (3 dB crest factor) (18) This is valuable information to consider when attempting to estimate the heat dissipation requirements for the amplifier system. Comparing the absolute worst case, which is 2 W of continuous power output with a 3 dB crest factor, against 12 dB and 15 dB applications drastically affects maximum ambient temperature ratings for the system. Using the power dissipation curves for a 5-V, 4-Ω system, the internal dissipation in the TPA005D02 and maximum ambient temperatures is shown in Table 4. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 21 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 APPLICATION INFORMATION crest factor and thermal considerations (continued) Table 4. TPA005D02 Power Rating, 5-V, 4-Ω, Stereo PEAK OUTPUT POWER (W) AVERAGE OUTPUT POWER POWER DISSIPATION (W/Channel) MAXIMUM AMBIENT TEMPERATURE 4 2 W (3 dB) 0.56 125°C 4 1000 mW (6 dB) 0.30 136°C 4 500 mW (9 dB) 0.23 139°C 4 250 mW (12 dB) 0.20 141°C 4 120 mW (15 dB) 0.14 143°C 4 63 mW (18 dB) 0.09 146°C ÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁ DISSIPATION RATING TABLE PACKAGE DCA TA ≤ 25°C 5.6 W DERATING FACTOR 44.8 mW/°C TA = 70°C 3.5 W TA = 85°C 2.9 W The maximum ambient temperature depends on the heatsinking ability of the PCB system. Using the 0 CFM data from the dissipation rating table, the derating factor for the DCA package with 6.9 in2 of copper area on a multilayer PCB is 44.8 mW/°C. Converting this to ΘJA: Θ JA 1 + Derating 1 + 0.0448 + 22.3°CńW (19) To calculate maximum ambient temperatures, first consider that the numbers from the dissipation graphs are per channel so the dissipated heat needs to be doubled for two channel operation. Given ΘJA, the maximum allowable junction temperature, and the total internal dissipation, the maximum ambient temperature can be calculated with the following equation. The maximum recommended junction temperature for the TPA005D02 is 150 °C. The internal dissipation figures are taken from the Efficiency vs Output Power graphs. T A Max + TJ Max * ΘJA PD + 150 * 22.3 (0.14 2) + 143°C (15 dB crest factor) + 150 * 22.3 (0.56 2) + 125°C (3dB crest factor) (20) NOTE: Internal dissipation of 0.6 W is estimated for a 2-W system with a 15 dB crest factor per channel. Table 4 shows that for some applications no airflow is required to keep junction temperatures in the specified range. The TPA005D02 is designed with thermal protection that turns the device off when the junction temperature surpasses 150°C to prevent damage to the IC. Table 4 was calculated for maximum listening volume without distortion. When the output level is reduced the numbers in the table change significantly. Also, using 8-Ω speakers dramatically increases the thermal performance by increasing amplifier efficiency. 22 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 THERMAL INFORMATION The thermally enhanced DCA package is based on the 56-pin TSSOP, but includes a thermal pad (see Figure 59) to provide an effective thermal contact between the IC and the PWB. Traditionally, surface-mount and power have been mutually exclusive terms. A variety of scaled-down TO-220-type packages have leads formed as gull wings to make them applicable for surface-mount applications. These packages, however, have only two shortcomings: they do not address the very low profile requirements (< 2 mm) of many of today’s advanced systems, and they do not offer a terminal-count high enough to accommodate increasing integration. On the other hand, traditional low-power surface-mount packages require power-dissipation derating that severely limits the usable range of many high-performance analog circuits. The PowerPAD package (thermally enhanced TSSOP) combines fine-pitch surface-mount technology with thermal performance comparable to much larger power packages. The PowerPAD package is designed to optimize the heat transfer to the PWB. Because of the very small size and limited mass of a TSSOP package, thermal enhancement is achieved by improving the thermal conduction paths that remove heat from the component. The thermal pad is formed using a patented lead-frame design and manufacturing technique to provide a direct connection to the heat-generating IC. When this pad is soldered or otherwise thermally coupled to an external heat dissipator, high power dissipation in the ultra-thin, fine-pitch, surface-mount package can be reliably achieved. Thermal Pad DIE Side View (a) DIE End View (b) Bottom View (c) Figure 22. Views of Thermally Enhanced DCA Package POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 23 TPA005D02 2-W STEREO CLASS-D AUDIO POWER AMPLIFIER SLOS227C – AUGUST 1998 – REVISED MARCH 2000 MECHANICAL DATA DCA (R-PDSO-G**) PowerPAD PLASTIC SMALL-OUTLINE PACKAGE 48 PINS SHOWN 0,27 0,17 0,50 48 0,08 M 25 Thermal Pad (See Note D) 6,20 6,00 8,30 7,90 0,15 NOM Gage Plane 1 24 0,25 A 0°– 8° 0,75 0,50 Seating Plane 0,15 0,05 1,20 MAX PINS ** 0,10 48 56 64 A MAX 12,60 14,10 17,10 A MIN 12,40 13,90 16,90 DIM 4073259/A 01/98 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 not to exceed 0,15. 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. 24 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