TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 D Fully Specified for 3.3-V and 5-V Operation D Wide Power Supply Compatibility D D D D D D OR DGN PACKAGE (TOP VIEW) 2.5 V – 5.5 V Power Supply Rejection at 217 Hz – 84 dB at VDD = 5 V – 81 dB at VDD = 3.3 V Output Power for RL = 8 Ω – 700 mW at VDD = 5 V – 250 mW at VDD = 3.3 V Ultralow Supply Current in Shutdown Mode . . . 1.5 nA Thermal and Short-Circuit Protection Surface-Mount Packaging – SOIC – PowerPAD MSOP – MicroStar Junior (BGA) SHUTDOWN BYPASS IN+ IN– 1 8 2 7 3 6 4 5 VO – GND VDD VO + MicroStar Juniort (GQS) Package (TOP VIEW) (E2) SHUTDOWN (E3) BYPASS (E4) IN+ (E5) IN– (A2) (A3) (A4) (A5) VO– GND VDD VO+ (SIDE VIEW) NOTE: The shaded terminals are used for thermal connections to the ground plane. description The TPA751 is a bridge-tied load (BTL) audio power amplifier developed especially for low-voltage applications where internal speakers are required. Operating with a 3.3-V supply, the TPA751 can deliver 250-mW of continuous power into a BTL 8-Ω load at less than 0.6% THD+N throughout voice band frequencies. Although this device is characterized out to 20 kHz, its operation is optimized for narrower band applications such as wireless communications. The BTL configuration eliminates the need for external coupling capacitors on the output in most applications, which is particularly important for small battery-powered equipment. This device features a shutdown mode for power-sensitive applications with a supply current of 1.5 nA during shutdown. The TPA751 is available in a 3.0 × 3.0 mm MicroStar Junior (BGA), 8-pin SOIC surface-mount package and a surface-mount PowerPAD MSOP. VDD 6 RF VDD/2 Audio Input RI CI 4 IN – 3 IN+ 2 BYPASS VDD CS – VO+ 5 + CB – VO– 8 + 700 mW 7 GND From System Control 1 SHUTDOWN Bias Control 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 and MicroStar Junior are trademarks of Texas Instruments. Copyright 2002, 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 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 AVAILABLE OPTIONS PACKAGED DEVICES MicroStar-Junior (BGA)‡ (GQS) SMALL OUTLINE† (D) MSOP‡ (DGN) TPA751GQS TPA751D TPA751DGN Device Package symbolization TPA751 TPA751 ATC † In the SOIC package, the maximum RMS output power is thermally limited to 350 mW; 700 mW peaks can be driven, as long as the RMS value is less than 350 mW. ‡ The D, DGN, and GQS packages are available taped and reeled. To order a taped and reeled part, add the suffix R to the part number (e.g., TPA751DR). Terminal Functions TERMINAL NO. NAME I/O DESCRIPTION I BYPASS is the tap to the voltage divider for internal mid-supply bias. This terminal should be connected to a 0.1-µF to 2.2-µF capacitor when used as an audio amplifier. GQS D, DGN E3 2 GND § 7 IN – E5 4 I IN – is the inverting input. IN – is typically used as the audio input terminal. IN+ E4 3 I IN + is the noninverting input. IN + is typically tied to the BYPASS terminal for SE input. SHUTDOWN E2 1 I SHUTDOWN places the entire device in shutdown mode when held low (IDD = 1.5 nA). VDD VO+ A4 6 A5 5 O VDD is the supply voltage terminal. VO+ is the positive BTL output. BYPASS GND is the ground connection. VO– A2 8 O VO– is the negative BTL output. § A1, A3, A5, B1–B5, C1–C5, D1–D5 are electrical and thermal connections to the ground plane. absolute maximum ratings over operating free-air temperature range (unless otherwise noted)¶ Supply voltage, VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 V Input voltage, VI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to VDD +0.3 V Continuous total power dissipation . . . . . . . . . . . . . . . . . . . . . Internally limited (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. DISSIPATION RATING TABLE PACKAGE GQS|| TA = 25°C 1.66 W|| D DGN DERATING FACTOR 13.3 mW/°C TA = 70°C 1.06 W TA = 85°C 866 mW 725 mW 5.8 mW/°C 464 mW 377 mW 2.14 W# 17.1 mW/°C 1.37 W 1.11 W # See the Texas Instruments document, PowerPAD Thermally Enhanced Package Application Report (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 that document. || See the Texas Instruments document, MicroStar Junior Made Easy Application Brief (SSYA009A) for board layout information on the MicroStar Junior package. 2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 recommended operating conditions ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ MIN MAX 2.5 5.5 Supply voltage, VDD High-level input voltage, VIH, (SHUTDOWN) 0.9VDD V V Low-level input voltage, VIL, (SHUTDOWN) Operating free-air temperature, TA UNIT 0.1VDD 85 – 40 V °C electrical characteristics at specified free-air temperature, VDD = 3.3 V, TA = 25°C (unless otherwise noted) ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ PARAMETER TEST CONDITIONS |VOS| Output offset voltage (measured differentially) SHUTDOWN = VDD, RL = 8 Ω, RF = 10 kΩ PSRR Power supply rejection ratio IDD IDD(SD) Supply current VDD = 3.2 V to 3.4 V SHUTDOWN = VDD, RF = 10 kΩ Supply current, shutdown mode (see Figure 4) SHUTDOWN = 0 V, RF = 10 kΩ MIN TYP MAX 20 85 UNIT mV dB 1.25 2.5 1.5 1000 mA nA |IIH| SHUTDOWN, VDD = 3.3 V, Vi = VDD 1 µA |IIL| SHUTDOWN, VDD = 3.3 V, Vi = 0 V 1 µA operating characteristics, VDD = 3.3 V, TA = 25°C, RL = 8 Ω PARAMETER TEST CONDITIONS MIN TYP MAX Output power, See Note 1 THD = 0.2%, See Figure 9 Total harmonic distortion plus noise f = 200 Hz to 4 kHz, See Figure 7 0.55% BOM B1 Maximum output power bandwidth PO = 250 mW, AV = –2 V/V, THD = 2%, See Figure 7 20 kHz Unity-gain bandwidth Open loop, See Figure 15 1.4 MHz Supply ripple rejection ratio f = 1 kHz, CB = 1 µF, See Figure 2 79 dB Noise output voltage AV = –1V/V, CB = 0.1 µF, See Figure 19 17 µV(rms) Vn 250 UNIT PO THD + N mW NOTE 1: Output power is measured at the output terminals of the device at f = 1 kHz. electrical characteristics at specified free-air temperature, VDD = 5 V, TA = 25°C (unless otherwise noted) ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ PARAMETER TEST CONDITIONS |VOS| Output offset voltage (measured differentially) SHUTDOWN = VDD, RL = 8 Ω, RF = 10 kΩ PSRR Power supply rejection ratio IDD IDD(SD) Supply current VDD = 4.9 V to 5.1 V SHUTDOWN = VDD, RF = 10 kΩ Supply current, shutdown mode (see Figure 4) SHUTDOWN = 0 V, RF = 10 kΩ MIN TYP MAX UNIT 20 mV 1.45 2.5 mA 5 78 dB 1500 nA |IIH| SHUTDOWN, VDD = 5.5 V, Vi = VDD 1 µA |IIL| SHUTDOWN, VDD = 5.5 V, Vi = 0 V 1 µA operating characteristics, VDD = 5 V, TA = 25°C, RL = 8 Ω ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ PARAMETER TEST CONDITIONS MIN PO THD + N Output power THD = 0.5%, See Figure 13 Total harmonic distortion plus noise f = 200 Hz to 4 kHz, See Figure 11 BOM B1 Maximum output power bandwidth PO = 250 mW, AV = –2 V/V, THD = 2%, See Figure 11 Unity-gain bandwidth Open loop, See Figure 16 TYP 700† MAX UNIT mW 0.5% 20 kHz 1.4 MHz Supply ripple rejection ratio f = 1 kHz, See Figure 2 80 dB CB = 1 µF, Vn Noise output voltage AV = –1 V/V, See Figure 20 17 CB = 0.1 µF, µV(rms) † The GQS and DGN packages, properly mounted, can conduct 700 mW RMS power continuously. The D package, can only conduct 350 mW RMS power continuously, with peaks to 700 mW. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 3 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 PARAMETER MEASUREMENT INFORMATION VDD 6 RF VDD/2 Audio Input RI CI VDD CS 4 IN – 3 IN+ 2 BYPASS VO+ 5 – + RL = 8 Ω CB – VO– 8 + 7 GND VDD 1 SHUTDOWN Bias Control Figure 1. BTL Mode Test Circuit TYPICAL CHARACTERISTICS Table of Graphs FIGURE kSVR Supply ripple rejection ratio vs Frequency IDD Supply current vs Supply voltage 3, 4 vs Supply voltage 5 PO Output power vs Load resistance vs Frequency THD + N Vn PD 4 Total harmonic distortion plus noise vs Output power 2 6 7, 8, 11, 12 9, 10, 13, 14 Open loop gain and phase vs Frequency 15, 16 Closed loop gain and phase vs Frequency 17, 18 Output noise voltage vs Frequency 19, 20 Power dissipation vs Output power 21, 22 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 TYPICAL CHARACTERISTICS SUPPLY RIPPLE REJECTION RATIO vs FREQUENCY SUPPLY CURRENT vs SUPPLY VOLTAGE 1.8 RL = 8 Ω CB = 1 µF Inputs Floating –20 SHUTDOWN = VDD RF = 10 kΩ 1.6 I DD – Supply Current – mA –10 –30 –40 –50 –60 –70 VDD = 3.3 V –80 –100 20 100 1.4 1.2 1 0.8 VDD = 5 V –90 1k 10k 0.6 2.5 20k 3.5 3 f – Frequency – Hz 4 4.5 5 5.5 VDD – Supply Voltage – V Figure 2 Figure 3 SUPPLY CURRENT vs SUPPLY VOLTAGE 10 9 SHUTDOWN = 0 V RF = 10 kΩ 8 I DD – Supply Current – nA k SVR – Supply Ripple Rejection Ratio – dB 0 7 6 5 4 3 2 1 0 2.5 3 3.5 4 4.5 5 5.5 VDD – Supply Voltage – V Figure 4 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 TYPICAL CHARACTERISTICS OUTPUT POWER vs SUPPLY VOLTAGE 1000 THD+N 1% f = 1 kHz PO – Output Power – mW 800 600 RL = 8 Ω RL = 32 Ω 400 200 0 2.5 3 3.5 4 4.5 5 5.5 VDD – Supply Voltage – V Figure 5 OUTPUT POWER vs LOAD RESISTANCE 800 THD+N = 1% f = 1 kHz PO – Output Power – mW 700 600 VDD = 5 V 500 400 300 VDD = 3.3 V 200 100 0 8 16 24 32 40 48 56 RL – Load Resistance – Ω Figure 6 6 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 64 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 TYPICAL CHARACTERISTICS TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY 10 THD+N –Total Harmonic Distortion + Noise – % THD+N –Total Harmonic Distortion + Noise – % 10 VDD = 3.3 V PO = 250 mW RL = 8 Ω AV = –20 V/V 1 AV =– 10 V/V AV = –2 V/V 0.1 0.01 20 100 1k 10k VDD = 3.3 V RL = 8 Ω AV = –2 V/V PO = 50 mW 1 0.1 PO = 125 mW PO = 250 mW 0.01 20 20k 100 1k f – Frequency – Hz Figure 7 TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER 10 VDD = 3.3 V f = 1 kHz AV = –2 V/V THD+N –Total Harmonic Distortion + Noise – % THD+N –Total Harmonic Distortion + Noise – % 10 1 RL = 8 Ω 0.1 0.01 0.05 0.1 20k Figure 8 TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER 0 10k f – Frequency – Hz 0.15 0.2 0.25 0.3 0.35 0.4 f = 20 kHz 1 f = 10 kHz f = 1 kHz 0.1 f = 20 Hz 0.01 0.01 PO – Output Power – W VDD = 3.3 V RL = 8 Ω CB = 1 µF AV = –2 V/V 0.1 1 PO – Output Power – W Figure 9 Figure 10 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 7 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 TYPICAL CHARACTERISTICS TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY 10 VDD = 5 V PO = 700 mW RL = 8 Ω THD+N –Total Harmonic Distortion + Noise – % THD+N –Total Harmonic Distortion + Noise – % 10 AV = –20 V/V 1 AV = –10 V/V AV = –2 V/V 0.1 0.01 20 100 1k 10k 20k VDD = 5 V RL = 8 Ω AV = –2 V/V 1 PO = 700 mW 0.1 PO = 350 mW 0.01 20 100 f – Frequency – Hz 20k TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER 10 10 THD+N –Total Harmonic Distortion + Noise – % THD+N –Total Harmonic Distortion + Noise – % 10k Figure 12 TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER VDD = 5 V f = 1 kHz AV = –2 V/V 1 RL = 8 Ω 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 f = 20 kHz 1 f = 10 kHz f = 1 kHz f = 20 Hz 0.1 VDD = 5 V RL = 8 Ω CB = 1 µF AV = –2 V/V 0.01 0.01 PO – Output Power – W 0.1 PO – Output Power – W Figure 13 8 1k f – Frequency – Hz Figure 11 0.01 0.1 PO = 50 mW Figure 14 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 TYPICAL CHARACTERISTICS OPEN-LOOP GAIN AND PHASE vs FREQUENCY 80 180° VDD = 3.3 V RL = Open 70 140° Phase 100° 50 60° 40 20° 30 Gain 20 – 20° 10 Phase Open-Loop Gain – dB 60 –60° 0 –100° –10 –140° –20 –30 1 101 102 103 104 –180° f – Frequency – kHz Figure 15 OPEN-LOOP GAIN AND PHASE vs FREQUENCY 80 180° VDD = 5 V RL = Open 70 140° 60 100° 60° 40 20° 30 Gain 20 – 20° 10 Phase Open-Loop Gain – dB Phase 50 –60° 0 –100° –10 –140° –20 –30 1 101 102 103 104 –180° f – Frequency – kHz Figure 16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 9 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 TYPICAL CHARACTERISTICS CLOSED-LOOP GAIN AND PHASE vs FREQUENCY 1 180° Phase 0.75 170° 0.25 0 160° Gain –0.25 150° –0.5 –0.75 140° –1 –1.25 –1.5 Phase Closed-Loop Gain – dB 0.5 VDD = 3.3 V RL = 8 Ω PO = 250 mW 130° –1.75 –2 101 102 103 104 105 106 120° f – Frequency – Hz Figure 17 CLOSED-LOOP GAIN AND PHASE vs FREQUENCY 1 180° Phase 0.75 170° 0.25 0 160° Gain –0.25 150° –0.5 –0.75 140° –1 –1.25 –1.5 VDD = 5 V RL = 8 Ω PO = 700 m W 130° –1.75 –2 101 102 103 104 105 f – Frequency – Hz Figure 18 10 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 120° 106 Phase Closed-Loop Gain – dB 0.5 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 TYPICAL CHARACTERISTICS OUTPUT NOISE VOLTAGE vs FREQUENCY 100 VDD = 3.3 V BW = 22 Hz to 22 kHz RL = 8 Ω or 32 Ω AV = –1 V/V Vn – Output Noise Voltage – µV(rms) Vn – Output Noise Voltage – µV(rms) 100 OUTPUT NOISE VOLTAGE vs FREQUENCY VO BTL VO+ 10 1 20 100 1k 10k VDD = 5 V BW = 22 Hz to 22 kHz RL = 8 Ω or 32 Ω AV = –1 V/V VO BTL VO+ 10 1 20 20k 100 f – Frequency – Hz Figure 19 20k POWER DISSIPATION vs OUTPUT POWER 350 800 VDD = 3.3 V VDD = 5 V RL = 8 Ω RL = 8 Ω 700 PD – Power Dissipation – mW 300 PD – Power Dissipation – mW 10k Figure 20 POWER DISSIPATION vs OUTPUT POWER 250 200 150 100 1k f – Frequency – Hz RL = 32 Ω 50 600 500 400 300 200 RL = 32 Ω 100 0 0 200 400 600 0 0 PD – Output Power – mW 200 400 600 800 1000 PD – Output Power – mW Figure 21 Figure 22 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 11 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 APPLICATION INFORMATION bridged-tied load Figure 23 shows a linear audio power amplifier (APA) in a BTL configuration. The TPA751 BTL amplifier consists of two linear amplifiers driving both ends of the load. There are several potential benefits to this differential drive configuration, but initially consider power to the load. The differential drive to the speaker means that as one side is slewing up, the other side is slewing down, and vice versa. This, in effect, doubles the voltage swing on the load as compared to a ground referenced load. Plugging 2 × VO(PP) into the power equation, where voltage is squared, yields 4× the output power from the same supply rail and load impedance (see equation 1). V V (rms) + V Power + O(PP) 2 Ǹ2 2 (1) (rms) R L VDD VO(PP) RL 2x VO(PP) VDD –VO(PP) Figure 23. Bridge-Tied Load Configuration In a typical portable handheld equipment sound channel operating at 3.3 V, bridging raises the power into an 8-Ω speaker from a singled-ended (SE, ground reference) limit of 62.5 mW to 250 mW. In sound power that is a 6-dB improvement, which is loudness that can be heard. In addition to increased power, there are frequency response concerns. Consider the single-supply SE configuration shown in Figure 24. A coupling capacitor is required to block the dc offset voltage from reaching the load. These capacitors can be quite large (approximately 33 µF to 1000 µF), so they tend to be expensive, heavy, occupy valuable PCB area, and have the additional drawback of limiting low-frequency performance of the system. This frequency-limiting effect, due to the high pass filter network created with the speaker impedance and the coupling capacitance, is calculated with equation 2. fc + 12 1 2p R C L C (2) POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 APPLICATION INFORMATION bridged-tied load (continued) For example, a 68-µF capacitor with an 8-Ω speaker would attenuate low frequencies below 293 Hz. The BTL configuration cancels the dc offsets, which eliminates the need for the blocking capacitors. Low-frequency performance is then limited only by the input network and speaker response. Cost and PCB space are also minimized by eliminating the bulky coupling capacitor. VDD –3 dB VO(PP) CC RL VO(PP) fc Figure 24. Single-Ended Configuration and Frequency Response Increasing power to the load does carry a penalty of increased internal power dissipation. The increased dissipation is understandable considering that the BTL configuration produces 4× the output power of a SE configuration. Internal dissipation versus output power is discussed further in the thermal considerations section. BTL amplifier efficiency The primary cause of linear amplifier inefficiencies is voltage drop across the output stage transistors. There are two components of the internal voltage drop. One is the headroom or dc voltage drop that varies inversely to output power. The second component is due to the sinewave nature of the output. The total voltage drop, can be calculated by subtracting the RMS value of the output voltage from VDD. The internal voltage drop multiplied by the RMS value of the supply current, IDDrms, determines the internal power dissipation of the amplifier. An easy-to-use equation to calculate efficiency starts out being equal to the ratio of power from the power supply to the power delivered to the load. To accurately calculate the RMS values of power in the load and in the amplifier, the current and voltage waveform shapes must first be understood (see Figure 25). IDD VO IDD(RMS) V(LRMS) Figure 25. Voltage and Current Waveforms for BTL Amplifiers POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 13 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 APPLICATION INFORMATION BTL amplifier efficiency (continued) Although the voltages and currents for SE and BTL are sinusoidal in the load, currents from the supply are very different between SE and BTL configurations. In an SE application, the current waveform is a half-wave rectified shape, whereas in BTL it is a full-wave rectified waveform. This means RMS conversion factors are different. Keep in mind that for most of the waveform both the push and pull transistors are not on at the same time, which supports the fact that each amplifier in the BTL device only draws current from the supply for half the waveform. The following equations are the basis for calculating amplifier efficiency. Efficiency of a BTL amplifier + P P L (3) SUP where 2 V V V rms 2 , and V + P , therefore, P + P P + L L L LRMS Ǹ2 R 2R L L 1 and P SUP + V DD I DDavg and I DDavg + p ŕ p V P sin(t) dt + 1 p R 0 L 2V P P [cos(t)] p + 0 pR R L L V therefore, V DD P SUP pR L substituting PL and PSUP into equation 7, + P 2V 2 Efficiency of a BTL amplifier + where V P + VP 2 RL 2 V DD V P p RL + p VP 4 V DD Ǹ2 PL RL PL = Power delivered to load PSUP = Power drawn from power supply VLRMS = RMS voltage on BTL load RL = Load resistance VP = Peak voltage on BTL load IDDavg = Average current drawn from the power supply VDD = Power supply voltage ηBTL = Efficiency of a BTL amplifier therefore, h BTL + 14 p Ǹ2 PL RL 4V (4) DD POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 APPLICATION INFORMATION application schematics Figure 26 is a schematic diagram of a typical handheld audio application circuit, configured for a gain of –10 V/V. VDD 6 RF 50 kΩ Audio Input RI 10 kΩ CI VDD/2 4 IN – 3 IN+ 2 BYPASS VDD CS 1 µF – VO+ 5 + CB 2.2 µF – VO– 8 + 700 mW 7 GND 1 From System Control SHUTDOWN Bias Control Figure 26. TPA751 Application Circuit Figure 27 is a schematic diagram of a typical handheld audio application circuit, configured for a gain of –10 V/V with a differential input. VDD 6 RF 50 kΩ Audio Input– RI 10 kΩ CI RI 10 kΩ Audio Input+ 4 IN – 3 IN+ – VO+ 5 + RF 50 kΩ 2 CI VDD CS 1 µF VDD/2 BYPASS CB 2.2 µF – VO– 8 + 700 mW 7 GND From System Control 1 SHUTDOWN Bias Control Figure 27. TPA751 Application Circuit With Differential Input POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 15 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 APPLICATION INFORMATION application schematics (continued) It is important to note that using the additional RF resistor connected between IN+ and BYPASS causes VDD/2 to shift slightly, which could influence the THD+N performance of the amplifier. Although an additional external operational amplifier could be used to buffer BYPASS from RF, tests in the lab have shown that the THD+N performance is only minimally affected by operating in the fully differential mode as shown in Figure 27. The following sections discuss the selection of the components used in Figures 26 and 27. component selection gain setting resistors, RF and RI The gain for each audio input of the TPA751 is set by resistors RF and RI according to equation 5 for BTL mode. ǒ Ǔ BTL gain + * 2 R F R I (5) BTL mode operation brings about the factor 2 in the gain equation due to the inverting amplifier mirroring the voltage swing across the load. Given that the TPA751 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 6. Effective impedance + R R F I R )R F I (6) As an example, consider an input resistance of 10 kΩ and a feedback resistor of 50 kΩ. The BTL gain of the amplifier would be –10 V/V and the effective impedance at the inverting terminal would be 8.3 kΩ, which is well 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 when RF is greater than 50 kΩ. This, in effect, creates a low-pass filter network with the cutoff frequency defined in equation 7. –3 dB fc + 1 2p R C F F fc For example, if RF is 100 kΩ and CF is 5 pF, then fc is 318 kHz, which is well outside of the audio range. 16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 (7) TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 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 RI form a high-pass filter with the corner frequency determined in equation 8. –3 dB fc + 1 2p R C I I (8) 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 RI is 10 kΩ and the specification calls for a flat bass response down to 40 Hz. Equation 8 is reconfigured as equation 9. 1 C + I 2p R f c I (9) 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. 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. It is important to confirm the capacitor polarity in the application. power supply decoupling, CS The TPA751 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. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 17 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 APPLICATION INFORMATION midrail bypass capacitor, CB The midrail bypass capacitor, CB, is the most critical capacitor and serves several important functions. During start-up or recovery from shutdown mode, CB 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. The capacitor is fed from a 250-kΩ source inside the amplifier. To keep the start-up pop as low as possible, the relationship shown in equation 10 should be maintained. This insures the input capacitor is fully charged before the bypass capacitor is fully charged and the amplifier starts up. ǒCB 10 250 kΩ v 1 Ǔ ǒRF ) RIǓ CI (10) As an example, consider a circuit where CB is 2.2 µF, CI is 0.47 µF, RF is 50 kΩ, and RI is 10 kΩ. Inserting these values into the equation 10 we get: 18.2 v 35.5 which satisfies the rule. Bypass capacitor, CB, values of 0.1 µF to 2.2 µF ceramic or tantalum low-ESR capacitors are recommended for the best THD and noise performance. 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. 5-V versus 3.3-V operation The TPA751 operates over a supply range of 2.5 V to 5.5 V. This data sheet provides full specifications for 5-V and 3.3-V operation, as these are considered to be the two most common standard voltages. There are no special considerations for 3.3-V versus 5-V operation with respect to supply bypassing, gain setting, or stability. The most important consideration is that of output power. Each amplifier in TPA751 can produce a maximum voltage swing of VDD – 1 V. This means, for 3.3-V operation, clipping starts to occur when VO(PP) = 2.3 V as opposed to VO(PP) = 4 V at 5 V. The reduced voltage swing subsequently reduces maximum output power into an 8-Ω load before distortion becomes significant. Operation from 3.3-V supplies, as can be shown from the efficiency formula in equation 4, consumes approximately two-thirds the supply power of operation from 5-V supplies for a given output-power level. 18 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 APPLICATION INFORMATION headroom and thermal considerations Linear power amplifiers dissipate a significant amount of heat in the package under normal operating conditions. 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 TPA751 data sheet, one can see that when the TPA751 is operating from a 5-V supply into an 8-Ω speaker that 700 mW peaks are available. Converting watts to dB: P dB + 10 Log P P W + 10Log 700 mW + –1.5 dB 1W ref Subtracting the headroom restriction to obtain the average listening level without distortion yields: –1.5 dB – 15 dB = –16.5 (15 dB headroom) –1.5 dB – 12 dB = –13.5 (12 dB headroom) –1.5 dB – 9 dB = –10.5 (9 dB headroom) –1.5 dB – 6 dB = –7.5 (6 dB headroom) –1.5 dB – 3 dB = –4.5 (3 dB headroom) Converting dB back into watts: P W + 10 PdBń10 x P ref = 22 mW (15 dB headroom) = 44 mW (12 dB headroom) = 88 mW (9 dB headroom) = 175 mW (6 dB headroom) = 350 mW (3 dB headroom) 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 700 mW of continuous power output with 0 dB of headroom, 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, 8-Ω system, the internal dissipation in the TPA751 and maximum ambient temperatures is shown in Table 1. Table 1. TPA751 Power Rating, 5-V, 8-Ω, BTL D PACKAGE (SOIC) DGN PACKAGE (MSOP) GQS PACKAGE (MicroStar Junior) MAXIMUM AMBIENT TEMPERATURE MAXIMUM AMBIENT TEMPERATURE MAXIMUM AMBIENT TEMPERATURE 675 34°C 110°C 99°C 595 47°C 115°C 105°C 176 mW (6 dB) 475 68°C 122°C 114°C 700 88 mW (9 dB) 350 89°C 125°C 123°C 700 44 mW (12 dB) 225 111°C 125°C 125°C PEAK OUTPUT POWER (mW) AVERAGE OUTPUT POWER POWER DISSIPATION (mW) 700 700 mW 700 350 mW (3 dB) 700 Table 1 shows that the TPA751 can be used to its full 700-mW rating without any heat sinking in still air up to 110°C, 34°C, and 99°C for the DGN package (MSOP), D package (SOIC), and GQS (MicroStar Junior) package, respectively. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 19 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 MECHANICAL DATA GQS (S-PBGA-N24) PLASTIC BALL GRID ARRAY 3,20 2,80 2,00 TYP 0,50 0,50 E D 3,20 2,80 2,00 TYP C B A 1 2 3 4 5 (BOTTOM VIEW) 1,00 MAX Seating Plane 0,35 0,25 0,05 M 0,21 0,11 0,08 4201012/A 04/00 NOTES: A. All linear dimensions are in millimeters. B. This drawing is subject to change without notice. C. MicroStar Junior configuration 20 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 MECHANICAL DATA D (R-PDSO-G**) PLASTIC SMALL-OUTLINE PACKAGE 14 PINS SHOWN 0.050 (1,27) 0.020 (0,51) 0.014 (0,35) 14 0.010 (0,25) M 8 0.008 (0,20) NOM 0.244 (6,20) 0.228 (5,80) 0.157 (4,00) 0.150 (3,81) Gage Plane 0.010 (0,25) 1 7 0°–ā8° A 0.044 (1,12) 0.016 (0,40) Seating Plane 0.069 (1,75) MAX 0.010 (0,25) 0.004 (0,10) PINS ** 0.004 (0,10) 8 14 16 A MAX 0.197 (5,00) 0.344 (8,75) 0.394 (10,00) A MIN 0.189 (4,80) 0.337 (8,55) 0.386 (9,80) DIM 4040047 / D 10/96 NOTES: D. E. F. G. All linear dimensions are in inches (millimeters). This drawing is subject to change without notice. Body dimensions do not include mold flash or protrusion, not to exceed 0.006 (0,15). Falls within JEDEC MS-012 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 21 TPA751 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER WITH DIFFERENTIAL INPUTS SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002 MECHANICAL DATA DGN (S-PDSO-G8) PowerPAD PLASTIC SMALL-OUTLINE PACKAGE 0,38 0,25 0,65 8 0,25 M 5 Thermal Pad (See Note D) 0,15 NOM 3,05 2,95 4,98 4,78 Gage Plane 0,25 1 0°–ā6° 4 3,05 2,95 0,69 0,41 Seating Plane 1,07 MAX 0,15 0,05 0,10 4073271/A 04/98 NOTES: A. B. C. D. All linear dimensions are in millimeters. This drawing is subject to change without notice. Body dimensions include mold flash or protrusions. The package thermal performance may be enhanced by attaching an external heat sink to the thermal pad. This pad is electrically and thermally connected to the backside of the die and possibly selected leads. E. Falls within JEDEC MO-187 PowerPAD is a trademark of Texas Instruments. 22 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve 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 should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. 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