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LM4951ASDBD

LM4951ASDBD

  • 厂商:

    BURR-BROWN(德州仪器)

  • 封装:

    -

  • 描述:

    BOARD EVALUATION FOR LM4951A

  • 数据手册
  • 价格&库存
LM4951ASDBD 数据手册
LM4951A www.ti.com LM4951A SNAS453C – AUGUST 2008 – REVISED APRIL 2013 Wide Voltage Range 1.8 Watt Audio Amplifier With Short Circuit Protection Check for Samples: LM4951A FEATURES DESCRIPTION • The LM4951A is an audio power amplifier designed for applications with supply voltages ranging from 2.7V up to 9V. The LM4951A is capable of delivering 1.8W continuous average power with less than 1% THD+N into a bridge connected 8Ω load when operating from a 7.5VDC power supply. 1 23 • • • • • • • Pop & Click Circuitry Eliminates Noise During Turn-On and Turn-Off Transitions Wide Supply Voltage Range: 2.7V to 9V Low Current, Active-Low Shutdown Mode Low Quiescent Current Thermal Shutdown Protection Short Circuit Protection Unity-Gain Stable External Gain Configuration Capability APPLICATIONS • • • • • Portable Devices Cell Phones Laptop Computers Computer Speaker Systems MP3 Player Speakers KEY SPECIFICATIONS • • • • • Boomer™ audio power amplifiers were designed specifically to provide high quality output power with a minimal amount of external components. The LM4951A does not require bootstrap capacitors, or snubber circuits. The LM4951A features a low-power consumption active-low shutdown mode. Additionally, the LM4951A features an internal thermal shutdown protection mechanism and short circuit protection. The LM4951A contains advanced pop & click circuitry that eliminates noises which would otherwise occur during turn-on and turn-off transitions. The LM4951A is unity-gain stable and can be configured by external gain-setting resistors. Wide Voltage Range 2.7V to 9V Quiescent Power Supply Current (VDD = 7.5V) 2.5mA (typ) Power Output BTL at 7.5V, 1% THD 1.8 W (typ) Shutdown Current 0.01µA (typ) Fast Turn on Time 25ms (typ) 1 2 3 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. Boomer is a trademark of Texas Instruments. All other trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2008–2013, Texas Instruments Incorporated LM4951A SNAS453C – AUGUST 2008 – REVISED APRIL 2013 www.ti.com Typical Application Rf VDD Cs 1.0 PF VDD Ri 20k Ci 0.39 PF VIN - Vo- AMPA 1k Rc CBYPASS VIH 1.0 PF + CCHG 20k Control Bias Bypass 8: VIL Shutdown control 20k Shutdown + AMPB Vo+ GND Figure 1. Typical Bridge-Tied-Load (BTL) Audio Amplifier Application Circuit Connection Diagram Top View + Bypass 1 10 VO Shutdown 2 9 VDD CCHG 3 8 NC NC 4 7 GND VIN 5 6 VO - Figure 2. WSON Package See Package Number DPR0010A Pin Name and Function Pin Number 2 Name 1 Bypass 2 Shutdown Function Type ½ supply reference voltage bypass output. See sections POWER SUPPLY BYPASSING and SELECTING EXTERNAL COMPONENTS for more information. Shutdown control active low signal. A logic low voltage will put the LM4951A into Shutdown mode. Submit Documentation Feedback Analog Output Digital Input Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A LM4951A www.ti.com SNAS453C – AUGUST 2008 – REVISED APRIL 2013 Pin Name and Function (continued) Pin Number Name Function Type Input capacitor charge to decrease turn on time. See section Selecting Value A For RCfor more information. 3 CCHG Analog Output 4 NC No connection to die. Pin can be connected to any potential. No Connect 5 VIN Single-ended signal input pin. Analog Input 6 VO- Inverting output of amplifier. 7 GND 8 NC No connection to die. Pin can be connected to any potential. Analog Output Ground connection. Ground No Connect 9 VDD Power supply. 10 VO+ Non-Inverting output of amplifier. Power Exposed DAP NC No connect. Pin must be electrically isolated (floating) or connected to GND. Analog Output No Connect These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) (2) Supply Voltage 9.5V −65°C to +150°C Storage Temperature −0.3V to VDD + 0.3V Input Voltage Power Dissipation (3) Internally limited ESD Rating (4) ESD Rating 2000V (5) 200V Junction Temperature (TJMAX) Thermal Resistance 150°C θJA (WSON) (3) Soldering Information (1) (2) (3) (4) (5) 73°C/W AN-1187 (Literature Number SNOA401) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability and/or performance. Functional operation of the device and/or non-degradation at the s or other conditions beyond those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating Conditionsindicate conditions at which the device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect to the ground pin, unless otherwise specified. The Electrical Characteristics tables list ensured specifications under the listed Recommended Operating Conditions except as otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not ensured. The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature, TA. The maximum allowable power dissipation is PDMAX = (TJMAX - TA) / θJA or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4951A typical application (shown in Figure 1) with VDD = 7.5V, RL = 8Ω mono-BTL operation the max power dissipation is 1.42W. θJA = 73ºC/W. Human body model, applicable std. JESD22-A114C. Machine model, applicable std. JESD22-A115-A. Operating Ratings (1) (2) Temperature Range TMIN ≤ TA ≤ TMAX −40°C ≤ T A ≤ +85°C 2.7V ≤ VDD ≤ 9V Supply Voltage (1) (2) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability and/or performance. Functional operation of the device and/or non-degradation at the s or other conditions beyond those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating Conditionsindicate conditions at which the device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect to the ground pin, unless otherwise specified. The Electrical Characteristics tables list ensured specifications under the listed Recommended Operating Conditions except as otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not ensured. Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A 3 LM4951A SNAS453C – AUGUST 2008 – REVISED APRIL 2013 www.ti.com Electrical Characteristics VDD = 7.5V (1) (2) The following specifications apply for VDD = 7.5V, AV-BTL = 6dB, RL = 8Ω unless otherwise specified. Limits apply for TA = 25°C. Parameter LM4951A Test Conditions Typ (3) Limit (4) Units (Limits) mA (max) IDD Quiescent Power Supply Current VIN = 0V, IO = 0A, RL = 8Ω BTL 2.5 4.5 ISD Shutdown Current VSD = GND (5) 0.01 5 µA (max) VOS Output Offset Voltage 5 30 mV (max) VSDIH Shutdown Voltage Input High 1.2 V (min) VSDIL Shutdown Voltage Input Low RPULLDOWN Pull-down Resistor on SD pin TWU Wake-up Time CB = 1.0µF TSD Shutdown time CB = 1.0µF TSD Thermal Shutdown Temperature PO Output Power THD = 1% (max); f = 1kHz RL = 8Ω Mono BTL PO = 600mWRMS; f = 1kHz THD+N Total Harmonic Distortion + Noise AV-BTL = 6dB PO = 600mWRMS; f = 1kHz AV-BTL = 26dB εOS Output Noise PSRR Power Supply Rejection Ratio (1) (2) (3) (4) (5) (6) 4 A-Weighted Filter, Ri = Rf = 20kΩ Input Referred (6) VRIPPLE = 200mVp-p, f = 217Hz, CB = 1.0μF, Input Referred 0.4 V (max) 75 45 kΩ (min) 25 35 ms (max) 10 ms (max) 170 150 190 °C (min) °C (max) 1.8 1.5 W (min) 0.07 0.5 % (max) 0.35 % 10 µV 66 56 dB (min) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability and/or performance. Functional operation of the device and/or non-degradation at the s or other conditions beyond those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating Conditionsindicate conditions at which the device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect to the ground pin, unless otherwise specified. The Electrical Characteristics tables list ensured specifications under the listed Recommended Operating Conditions except as otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not ensured. Typical values represent most likely parametric norms at TA = +25ºC, and at the Recommended Operation Conditions at the time of product characterization and are not specified. Datasheet min/max specification limits are ensured by test or statistical analysis. Shutdown current is measured in a normal room environment. The Shutdown pin should be driven as close as possible to GND for minimum shutdown current. Noise measurements are dependent on the absolute values of the closed loop gain setting resistors (input and feedback resistors). Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A LM4951A www.ti.com SNAS453C – AUGUST 2008 – REVISED APRIL 2013 Electrical Characteristics VDD = 3.3V (1) (2) The following specifications apply for VDD = 3.3V, AV-BTL = 6dB, RL = 8Ω unless otherwise specified. Limits apply for TA = 25°C. Parameter Test Conditions LM4951A Typ (3) Limit (4) Units (Limits) mA (max) IDD Quiescent Power Supply Current VIN = 0V, IO = 0A, RL = 8Ω BTL 2.5 4.5 ISD Shutdown Current VSHUTDOWN = GND (5) 0.01 2 µA (max) VOS Output Offset Voltage 3 30 mV (max) VSDIH Shutdown Voltage Input High 1.2 V (min) VSDIL Shutdown Voltage Input Low 0.4 V (max) TWU Wake-up Time CB = 1.0µF TSD Shutdown time CB = 1.0µF 10 ms (max) PO Output Power THD = 1% (max); f = 1kHz RL = 8Ω Mono BTL 280 230 mW (min) 0.07 0.5 % (max) PO = 100mWRMS = 1kHz THD+N Total Harmonic Distortion + Noise AV-BTL = 6dB PO = 100mWRMS; f = 1kHz AV-BTL = 26dB εOS Output Noise PSRR Power Supply Rejection Ratio (1) (2) (3) (4) (5) (6) A-Weighted Filter, Ri = Rf = 20kΩ Input Referred, (6) VRIPPLE = 200mVp-p, f = 217Hz, CB = 1μF, Input Referred 25 ms 0.35 % 10 µV 71 61 dB (min) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability and/or performance. Functional operation of the device and/or non-degradation at the s or other conditions beyond those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating Conditionsindicate conditions at which the device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect to the ground pin, unless otherwise specified. The Electrical Characteristics tables list ensured specifications under the listed Recommended Operating Conditions except as otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not ensured. Typical values represent most likely parametric norms at TA = +25ºC, and at the Recommended Operation Conditions at the time of product characterization and are not specified. Datasheet min/max specification limits are ensured by test or statistical analysis. Shutdown current is measured in a normal room environment. The Shutdown pin should be driven as close as possible to GND for minimum shutdown current. Noise measurements are dependent on the absolute values of the closed loop gain setting resistors (input and feedback resistors). Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A 5 LM4951A SNAS453C – AUGUST 2008 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics 10 THD+N vs Frequency VDD = 3.3V, PO = 100mW, AV = 6dB 10 THD+N vs Frequency VDD = 3.3V, PO = 100mW, AV = 26dB 5 2 1 THD+N (%) THD+N (%) 1 0.5 0.2 0.1 0.1 0.05 0.02 0.01 20 200 2k 0.01 20 20k Figure 4. THD+N vs Frequency VDD = 5V, PO = 400mW, AV = 6dB THD+N vs Frequency VDD = 5V, PO = 400mW, AV = 26dB 10 5 5 2 2 1 1 0.5 0.2 0.5 0.2 0.1 0.1 0.05 0.05 0.02 0.02 0.01 20 50 100 200 500 1k 2k 0.01 20 5k 10k 20k FREQUENCY (Hz) 10 5k 10k 20k Figure 3. THD+N (%) THD+N (%) 10 50 100 200 500 1k 2k FREQUENCY (Hz) FREQUENCY (Hz) 50 100 200 500 1k 2k 5k 10k 20k FREQUENCY (Hz) Figure 5. Figure 6. THD+N vs Frequency VDD = 7.5V, PO = 600mW, AV = 6dB THD+N vs Frequency VDD = 7.5V, PO = 600mW, AV = 26dB 10 5 5 2 THD+N (%) THD+N (%) 1 0.5 0.2 0.1 2 1 0.5 0.05 0.2 0.02 0.01 20 0.1 50 100 200 500 1k 2k 5k 10k 20k FREQUENCY (Hz) 200 2k 20k FREQUENCY (Hz) Figure 7. 6 20 Figure 8. Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A LM4951A www.ti.com SNAS453C – AUGUST 2008 – REVISED APRIL 2013 Typical Performance Characteristics (continued) 10 THD+N vs Output Power VDD = 3.3V, f = 1kHz, AV = 6dB THD+N vs Output Power VDD = 3.3V, f = 1kHz, AV = 26dB 10 1 THD+N (%) THD+N (%) 5 0.1 2 1 0.5 0.2 0.01 30m 10m 0.1 10m 500m 100m 20m OUTPUT POWER (W) 30m 50m 70m 100m 300m 500m 40m 60m 80m 200m 400m OUTPUT POWER (W) Figure 9. Figure 10. THD+N vs Output Power VDD = 5V, f = 1kHz, AV = 6dB 10 THD+N vs Output Power VDD = 5V, f = 1kHz, AV = 26dB 10 5 5 2 THD+N (%) THD+N (%) 1 0.5 0.2 0.1 2 1 0.5 0.05 0.2 0.02 0.01 10m 20m 50m 100m 200m 500m 0.1 10m 20m 1 OUTPUT POWER (W) 500m 1 OUTPUT POWER (W) Figure 11. 10 50m 100m 200m Figure 12. THD+N vs Output Power VDD = 7.5V, f = 1kHz, AV = 6dB 10 THD+N vs Output Power VDD = 7.5V, f = 1kHz, AV = 26dB 5 5 1 THD+N (%) THD+N (%) 2 0.5 0.2 0.1 2 1 0.5 0.05 0.2 0.02 0.01 10m 20m 50m 100m 200m 500m 1 2 3 0.1 10m 20m 50m 100m 200m 500m 1 2 3 OUTPUT POWER (W) OUTPUT POWER (W) Figure 13. Figure 14. Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A 7 LM4951A SNAS453C – AUGUST 2008 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) Power Supply Rejection vs Frequency VDD = 3.3V, AV = 6dB, VRIPPLE = 200mVP-P Input Terminated into 10Ω Power Supply Rejection vs Frequency VDD = 3.3V, AV = 26dB, VRIPPLE = 200mVP-P Input Terminated into 10Ω +0 -10 -20 PSRR (dB) PSRR (dB) -30 -40 -50 -60 -70 -80 -90 -100 20 50 100 200 500 1k 2k +0 -2.5 -5 -7.5 -10 -12.5 -15 -17.5 -20 -22.5 -25 -27.5 -30 -32.5 -35 -37.5 -40 -42.5 -45 -47.5 -50 -52.5 -55 -57.5 -60 20 5k 10k 20k Figure 16. Power Supply Rejection vs Frequency VDD = 5V, AV = 6dB, VRIPPLE = 200mVP-P Input Terminated into 10Ω Power Supply Rejection vs Frequency VDD = 5V, AV = 26dB, VRIPPLE = 200mVP-P Input Terminated into 10Ω -10 -20 PSRR (dB) PSRR (dB) -30 -40 -50 -60 -70 -80 -90 -100 20 50 100 200 500 1k 2k +0 -2.5 -5 -7.5 -10 -12.5 -15 -17.5 -20 -22.5 -25 -27.5 -30 -32.5 -35 -37.5 -40 -42.5 -45 -47.5 -50 -52.5 -55 -57.5 -60 20 5k 10k 20k 50 100 200 500 1k 2k 5k 10k 20k FREQUENCY (Hz) FREQUENCY (Hz) Figure 17. Figure 18. Power Supply Rejection vs Frequency VDD = 7.5V, AV = 6dB, VRIPPLE = 200mVP-P Input Terminated into 10Ω Power Supply Rejection vs Frequency VDD = 7.5V, AV = 26dB, VRIPPLE = 200mVP-P Input Terminated into 10Ω +0 -10 -20 PSRR (dB) -30 PSRR (dB) 5k 10k 20k Figure 15. +0 -40 -50 -60 -70 -80 -90 -100 20 50 100 200 500 1k 2k 5k 10k 20k +0 -2.5 -5 -7.5 -10 -12.5 -15 -17.5 -20 -22.5 -25 -27.5 -30 -32.5 -35 -37.5 -40 -42.5 -45 -47.5 -50 -52.5 -55 -57.5 -60 20 50 100 200 500 1k 2k 5k 10k 20k FREQUENCY (Hz) FREQUENCY (Hz) Figure 19. 8 50 100 200 500 1k 2k FREQUENCY (Hz) FREQUENCY (Hz) Figure 20. Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A LM4951A www.ti.com SNAS453C – AUGUST 2008 – REVISED APRIL 2013 Typical Performance Characteristics (continued) Noise Floor VDD = 3.3V, AV = 6dB, Ri = Rf = 20kΩ BW < 80kHz, A-weighted Noise Floor VDD = 3V, AV = 26dB, Ri = 20kΩ, Rf = 200kΩ BW < 80kHz, A-weighted 30P OUTPUT NOISE VOLTAGE (V) OUTPUT NOISE VOLTAGE (V) 50P 40P 20P 10P 9P 8P 7P 6P 5P 4P 3P 2P 150P 120P 100P 95P 90P 85P 82P 75P 72P 65P 62P 55P 52P 50P 1P 20 50 100 200 500 1k 2k 20 5k 10k 20k 50 100 200 500 1k 2k 5k 10k 20k FREQUENCY (Hz) FREQUENCY (Hz) Figure 21. Figure 22. Noise Floor VDD = 5V, AV = 6dB, Ri = Rf = 20kΩ BW < 80kHz, A-weighted Noise Floor VDD = 5V, AV = 26dB, Ri = 20kΩ, Rf = 200kΩ BW < 80kHz, A-weighted 30P OUTPUT NOISE VOLTAGE (V) OUTPUT NOISE VOLTAGE (V) 50P 40P 20P 10P 9P 8P 7P 6P 5P 4P 3P 2P 150P 120P 100P 95P 90P 85P 82P 75P 72P 65P 62P 55P 52P 50P 1P 20 50 100 200 500 1k 2k 20 5k 10k 20k 50 100 200 500 1k 2k 5k 10k 20k FREQUENCY (Hz) FREQUENCY (Hz) Figure 23. Figure 24. Noise Floor VDD = 7.5V, AV = 6dB, Ri = Rf = 20kΩ BW < 80kHz, A-weighted Noise Floor VDD = 7.5V, AV = 26dB, Ri = 20kΩ, Rf = 200kΩ BW < 80kHz, A-weighted 30P OUTPUT NOISE VOLTAGE (V) OUTPUT NOISE VOLTAGE (V) 50P 40P 20P 10P 9P 8P 7P 6P 5P 4P 3P 2P 150P 120P 100P 95P 90P 85P 82P 75P 72P 65P 62P 55P 52P 50P 1P 20 50 100 200 500 1k 2k 5k 10k 20k 20 50 100 200 500 1k 2k 5k 10k 20k FREQUENCY (Hz) FREQUENCY (Hz) Figure 25. Figure 26. Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A 9 LM4951A SNAS453C – AUGUST 2008 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) Power Dissipation vs Output Power VDD = 3.3V, RL = 8Ω, f = 1kHz Power Dissipation vs Output Power VDD = 7.5V, RL = 8Ω, f = 1kHz 1600 300 POWER DISSIPATION (mW) POWER DISSIPATION (mW) 1400 250 200 150 100 50 1200 1000 800 600 400 200 0 0 0 50 100 150 200 250 0 300 200 400 600 800 1000 1200 1400 OUTPUT POWER (mW) OUTPUT POWER (mW) Figure 27. Figure 28. Supply Current vs Supply Voltage RL = 8Ω, VIN = 0V, Rsource = 50Ω Clipping Voltage vs Supply Voltage RL = 8Ω, from top to bottom: Negative Voltage Swing; Positive Voltage Swing 2.5 1.4 DROPOUT VOPLTAGE (V) SUPPLY CURRENT (mA) 1.2 2 1.5 1 0.5 1 0.8 0.6 0.4 0.2 0 2 3 4 5 6 7 8 9 0 10 0 2 SUPPLY VOLTAGE (V) 6 8 10 Figure 30. Output Power vs Supply Voltage RL = 8Ω, from top to bottom: THD+N = 10%, THD+N = 1% Output Power vs Load Resistance VDD = 3.3V, f = 1kHz from top to bottom: THD+N = 10%, THD+N = 1% 4 450 3.5 400 OUTPUT POWER (mW) OUTPUT POWER (mW) Figure 29. 3 2.5 2 1.5 1 0.5 350 300 250 200 150 100 50 0 0 2.7 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 0 20 40 60 80 100 LOAD RESISTANCE (W) SUPPLY VOLTAGE (V) Figure 31. 10 4 SUPPLY VOLTAGE (V) Figure 32. Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A LM4951A www.ti.com SNAS453C – AUGUST 2008 – REVISED APRIL 2013 Typical Performance Characteristics (continued) Output Power vs Load Resistance VDD = 7.5V, f = 1kHz from top to bottom: THD+N = 10%, THD+N = 1% Frequency Response vs Input Capacitor Size RL = 8Ω from top to bottom: Ci = 1.0µF, Ci = 0.39µF, Ci = 0.039µF 3000 20 2500 12 OUTPUT LEVEL (dB) OUTPUT POWER (mW) 16 2000 1500 1000 8 4 0 -4 -8 -12 -16 -20 500 -24 -28 0 8 16 32 48 64 80 20 96 112 LOAD RESISTANCE (W) 50 100 200 500 1k 2k 5k 10k 20k FREQUENCY (Hz) Figure 33. Figure 34. Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A 11 LM4951A SNAS453C – AUGUST 2008 – REVISED APRIL 2013 www.ti.com APPLICATION INFORMATION BRIDGE CONFIGURATION EXPLANATION As shown in Figure 1, the LM4951A consists of two operational amplifiers that drive a speaker connected between their outputs. The value of input and feedback resistors determine the gain of each amplifier. External resistors Ri and Rf set the closed-loop gain of AMPA, whereas two 20kΩ internal resistors set AMPB's gain to -1. Figure 1 shows that AMPA's output serves as AMPB's input. This results in both amplifiers producing signals identical in magnitude, but 180° out of phase. Taking advantage of this phase difference, a load is placed between AMPA and AMPB and driven differentially (commonly referred to as "bridge-tied load"). This results in a differential, or BTL, gain of: AVD = 2(Rf/ Ri) (V/V) (1) Bridge mode amplifiers are different from single-ended amplifiers that drive loads connected between a single amplifier's output and ground. For a given supply voltage, bridge mode has an advantage over the single-ended configuration: its differential output doubles the voltage swing across the load. Theoretically, this produces four times the output power when compared to a single-ended amplifier under the same conditions. This increase in attainable output power assumes that the amplifier is not current limited and that the output signal is not clipped. Under rare conditions, with unique combinations of high power supply voltage and high closed loop gain settings, the LM4951A may exhibit low frequency oscillations. Another advantage of the differential bridge output is no net DC voltage across the load. This is accomplished by biasing AMP1's and AMP2's outputs at half-supply. This eliminates the coupling capacitor that single supply, single-ended amplifiers require. Eliminating an output coupling capacitor in a typical single-ended configuration forces a single-supply amplifier's half-supply bias voltage across the load. This increases internal IC power dissipation and may permanently damage loads such as speakers. POWER DISSIPATION The LM4951A's dissipation when driving a BTL load is given by Equation 2. For a 7.5V supply and a single 8Ω BTL load, the dissipation is 1.42W. PDMAX-MONOBTL = 4(VDD) 2/ 2π2RL (W) (2) The maximum power dissipation point given by Equation 2 must not exceed the power dissipation given by Equation 3: PDMAX = (TJMAX - TA) / θJA (3) The LM4951A's TJMAX = 150°C. In the SD package, the LM4951A's θJA is 73°C/W when the metal tab is soldered to a copper plane of at least 1in2. This plane can be split between the top and bottom layers of a two-sided PCB. Connect the two layers together under the tab with an array of vias. At any given ambient temperature TA, use Equation 3 to find the maximum internal power dissipation supported by the IC packaging. Rearranging Equation 3 and substituting PDMAX for PDMAX' results in Equation 4. This equation gives the maximum ambient temperature that still allows maximum stereo power dissipation without violating the LM4951A's maximum junction temperature. TA = TJMAX - PDMAX-MONOBTLθJA (°C) (4) For a typical application with a 7.5V power supply and a BTL 8Ω load, the maximum ambient temperature that allows maximum stereo power dissipation without exceeding the maximum junction temperature is 46°C for the SD package. TJMAX = PDMAX-MONOBTLθJA + TA (°C) (5) Equation 5 gives the maximum junction temperature TJMAX. If the result violates the LM4951A's maximum junction temperature of 150°C, reduce the maximum junction temperature by reducing the power supply voltage or increasing the load resistance. Further allowance should be made for increased ambient temperatures. The above examples assume that a device is operating around the maximum power dissipation point. Since internal power dissipation is a function of output power, higher ambient temperatures are allowed as output power or duty cycle decreases. 12 Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A LM4951A www.ti.com SNAS453C – AUGUST 2008 – REVISED APRIL 2013 If the result of Equation 2 is greater than that of Equation 3, then decrease the supply voltage, increase the load impedance, or reduce the ambient temperature. Further, ensure that speakers rated at a nominal 8Ω do not fall below 6Ω. If these measures are insufficient, a heat sink can be added to reduce θJA. The heat sink can be created using additional copper area around the package, with connections to the ground pins, supply pin and amplifier output pins. Refer to the Typical Performance Characteristics curves for power dissipation information at lower output power levels. POWER SUPPLY BYPASSING As with any power amplifier, proper supply bypassing is critical for low noise performance and high power supply rejection. Applications that employ a voltage regulator typically use a 10µF in parallel with a 0.1µF filter capacitors to stabilize the regulator's output, reduce noise on the supply line, and improve the supply's transient response. However, their presence does not eliminate the need for a local 1.0µF tantalum bypass capacitance connected between the LM4951A's supply pins and ground. Do not substitute a ceramic capacitor for the tantalum. Doing so may cause oscillation. Keep the length of leads and traces that connect capacitors between the LM4951A's power supply pin and ground as short as possible. Connecting a larger capacitor, CBYPASS, between the BYPASS pin and ground improves the internal bias voltage's stability and improves the amplifier's PSRR. The PSRR improvements increase as the bypass pin capacitor value increases. Too large, however, increases turn-on time and can compromise the amplifier's click and pop performance. The selection of bypass capacitor values, especially CBYPASS, depends on desired PSRR requirements, click and pop performance, system cost, and size constraints. MICRO-POWER SHUTDOWN The LM4951A features an active-low micro-power shutdown mode. When active, the LM4951A's micro-power shutdown feature turns off the amplifier's bias circuitry, reducing the supply current. The low 0.01µA typical shutdown current is achieved by applying a voltage to the SHUTDOWN pin that is as near to GND as possible. A voltage that is greater than GND may increase the shutdown current. SELECTING EXTERNAL COMPONENTS Input Capacitor Value Selection Two quantities determine the value of the input coupling capacitor: the lowest audio frequency that requires amplification and desired output transient suppression. As shown in Figure 1, the input resistor (Ri) and the input capacitor (Ci) create a high-pass filter. The cutoff frequency can be found using Equation 6. fc = 1/2πRiCi (Hz) (6) As an example when using a speaker with a low frequency limit of 50Hz, Ci, using Equation 6 is 0.159µF with Ri set to 20kΩ. The values for Ci and Ri shown in Figure 1 allow the LM4951A to drive a high efficiency, full range speaker whose response extends down to 20Hz. Selecting Value A For RC The LM4951A is designed for very fast turn on time. The CCHG pin allows the input capacitor to charge quickly to improve click/pop performance. RC protects the CCHG pin from any over/under voltage conditions caused by excessive input signal or an active input signal when the device is in shutdown. The recommended value for RC is 1kΩ. If the input signal is less than VDD+0.3V and greater than -0.3V, and if the input signal is disabled when in shutdown mode, RC may be shorted out. OPTIMIZING CLICK AND POP REDUCTION PERFORMANCE The LM4951A contains circuitry that eliminates turn-on and shutdown transients ("clicks and pops"). For this discussion, turn-on refers to either applying the power supply voltage or when the micro-power shutdown mode is deactivated. As the VDD/2 voltage present at the BYPASS pin ramps to its final value, the LM4951A's internal amplifiers are configured as unity gain buffers. An internal current source charges the capacitor connected between the BYPASS pin and GND in a controlled manner. Ideally, the input and outputs track the voltage applied to the BYPASS pin. Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A 13 LM4951A SNAS453C – AUGUST 2008 – REVISED APRIL 2013 www.ti.com The gain of the internal amplifiers remains unity until the voltage on the bypass pin reaches VDD/2. As soon as the voltage on the bypass pin is stable, there is a delay to prevent undesirable output transients (“click and pops”). After this delay, the device becomes fully functional. THERMAL SHUTDOWN AND SHORT CIRCUIT PROTECTION The LM4951A has thermal shutdown and short circuit protection to fully protect the device. The thermal shutdown circuit is activated when the die temperature exceeds a safe temperature. The short circuit protection circuitry senses the output current. When the output current exceeds the threshold under a short condition, a short will be detected and the output deactivated until the short condition is removed. If the output current is lower than the threshold then a short will not be detected and the outputs will not be deactivated. Under such conditions the die temperature will increase and, if the condition persist to raise the die temperature to the thermal shutdown threshold, initiate a thermal shutdown response. Once the die cools the outputs will become active. RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT Figures 2–4 show the recommended two-layer PC board layout that is optimized for the SD10A. This circuit is designed for use with an external 7.5V supply 8Ω (min) speakers. Demonstration Board Circuit Figure 35. Demo Board Circuit 14 Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A LM4951A www.ti.com SNAS453C – AUGUST 2008 – REVISED APRIL 2013 Demonstration Board Layout Figure 36. Top Silkscreen Figure 37. Top Layer Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A 15 LM4951A SNAS453C – AUGUST 2008 – REVISED APRIL 2013 www.ti.com Figure 38. Bottom Layer Bill Of Materials Table 1. Bill Of Materials Designator Value Tolerance RIN1 20kΩ 1% 1/8W, 0805 Resistor Part Description R1 200kΩ 1% 1/8W, 0805 Resistor RPULLUP 100kΩ 1% 1/8W, 0805 Resistor R2 1kΩ 1% 1/8W, 0805 Resistor R4, R5 0Ω 1% 1/8W, 0805 Resistor Comments CIN1 0.39μF 10% Ceramic Capacitor, 25V, Size 1206 CSUPPLY 4.7μF 10% 16V Tantalum Capacitor, Size A CBYPASS 1μF 10% 16V Tantalum Capacitor, Size A C1 Not Used 0.100” 1x2 header, vertical mount U1 16 Input, Output, Vdd/GND Shutdown LM4951A, Mono, 1.8W, Audio Amplifier Submit Documentation Feedback DPR0010A package Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A LM4951A www.ti.com SNAS453C – AUGUST 2008 – REVISED APRIL 2013 REVISION HISTORY Rev Date 1.0 08/13/08 Initial release. Description 1.01 09/05/08 Text edits. Changes from Revision B (April 2013) to Revision C • Page Changed layout of National Data Sheet to TI format .......................................................................................................... 16 Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Product Folder Links: LM4951A 17 PACKAGE OPTION ADDENDUM www.ti.com 10-Dec-2020 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) LM4951ASD/NOPB ACTIVE WSON DPR 10 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 85 4951ASD LM4951ASDX/NOPB ACTIVE WSON DPR 10 4500 RoHS & Green SN Level-1-260C-UNLIM -40 to 85 4951ASD (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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