LM4925 www.ti.com SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 LM4925 BoomerTM Audio Power Amplifier Series 2 Cell, Single Ended Output, 40mW Stereo Headphone Audio Amplifier Check for Samples: LM4925 FEATURES DESCRIPTION * * * The unity gain stable LM4925 is both a mono differential output (for BTL operation) audio amplifier and a Single Ended (SE) stereo headphone amplifier. Operating on a single 3V supply, the mono-BTL mode delivers 410mW into an 8 load at 1% THD+N. In Single Ended stereo headphone mode, the amplifier delivers 40mW per channel into a 16 load at 1% THD+N. 1 23 * * * * * BTL Mode for Mono Speaker 2-Cell 1.5V to 3.6V Battery Operation Single Ended Headphone Operation with Output Coupling Capacitors Unity-Gain Stable "Click and Pop" Suppression Circuitry for Both Shutdown and Mute Active Low Micro-Power Shutdown Active-Low Mute Mode Thermal Shutdown Protection Circuitry APPLICATIONS * * Portable Two-Cell Audio Products Portable Two-Cell Electronic Devices KEY SPECIFICATIONS * * * * * Mono-BTL Output Power - (RL = 8, VDD = 3.0V, THD+N = 1%), 410mW (Typ) Single Ended Output Power Per Channel, - (RL = 16, VDD = 3.0V, THD+N = 1%), 40mW (Typ) Micropower Shutdown Current, 0.1A (Typ) Supply Voltage Operating Range, 1.5V < VDD < 3.6V PSRR 100Hz, VDD = 3V, BTL, 70dB (Typ) With the LM4925 packaged in the VSSOP and SON packages, the customer benefits include low profile and small size. This package minimizes PCB area and maximizes output power. The LM4925 features circuitry that reduces output transients ("clicks" and "pops") during device turn-on and turn-off, an externally controlled, low-power consumption, active-low shutdown mode, and thermal shutdown. Boomer audio power amplifiers are designed specifically to use few external components and provide high quality output power in a surface mount package. 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 (c) 2005-2013, Texas Instruments Incorporated LM4925 SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 www.ti.com Typical Application + IN A CBYPASS Bias Generator IN B SD MUTE VoA Click-Pop and Mode Control Logic SE/BTL + VoB Figure 1. Block Diagram Connection Diagrams In A SD Mute Bypass IN B 1 10 2 9 3 8 4 7 5 6 VDD VoA SE/BTL VoB GND Figure 2. VSSOP Package Top View See Package Number DGS for VSSOP Figure 3. SON Package Top View See Package Number DSC0010A 2 Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 LM4925 www.ti.com SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 Typical Connections Rf 50k Ci Ri Co + 0.47 PF 20k 100 PF Vin1 4.7 PF Cbypass Ci + 16: Bias Generator Ri 0.47 PF 20k Click-Pop and Mode Control Logic Vin2 Co + 100 PF 16: Rf 50k ShutDown and Mute Controller Figure 4. Typical Capacitive Couple (SE) Output Configuration Circuit Rf 20k Ci Ri 0.47 PF 20k Vin 1 Cbypass 4.7 PF + Bias Generator IN B ShutDown and Mute Controller VoA Click-Pop and Mode Control Logic VDD 8: + Rf 20k 20k Figure 5. Typical BTL Speaker Configuration Circuit 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. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 3 LM4925 SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 www.ti.com Absolute Maximum Ratings (1) (2) Supply Voltage 3.8V -65C to +150C Storage Temperature -0.3V to VDD +0.3V Input Voltage Power Dissipation (3) Internally limited ESD Susceptibility (4) 2000V ESD Susceptibility (5) 200V Junction Temperature Solder Information 150C Small Outline Package Vapor (2) (3) (4) (5) 215C Infrared (15 sec) 220C JA (typ) DGS Thermal Resistance (1) Phase (60sec) JA (typ) DSC0010A 175C/W 73C/W Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not ensure specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication of device performance. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications. The maximum power dissipation is dictated by TJMAX, JA, and the ambient temperature TA and must be derated at elevated temperatures. The maximum allowable power dissipation is PDMAX = (TJMAX - TA)/JA. For the LM4925, TJMAX = 150C. For the JAs, please see the Application Information section or the Absolute Maximum Ratings section. Human body model, 100pF discharged through a 1.5k resistor. Machine model, 220pF-240pF discharged through all pins. Operating Ratings Temperature Range 4 TMIN TA TMAX Supply Voltage Submit Documentation Feedback -40C TA +85C 1.5V VDD 3.6V Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 LM4925 www.ti.com SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 Electrical Characteristics VDD = 3.0V (1) (2) The following specifications apply for the circuit shown in Figure 4 for Single Ended Outputs (AV = 2.5V) and Figure 5 for BTL Outputs (AV-BTL = 2), unless otherwise specified. Limits apply for TA = 25C. Symbol Parameter Conditions 1.0 1.6 0.1 1 A (max) 2 10 mV (max) RL = 8, BTL, Figure 5 THD+N = 1%, f = 1kHz 410 350 mW (min) RL = 16, Figure 4, SE per Channel, THD+N = 1%, f = 1kHz 40 30 mW (min) 0.5 % (max) Quiescent Power Supply Current VIN = 0V, IO = 0A, RL = ISD Shutdown Current VSHUTDOWN = GND VOS Output Offset Voltage Output Power (6) THD+N Total Harmonic Distortion + Noise VNO Output Voltage Noise Crosstalk PSRR Power Supply Rejection Ratio Units (Limits) Limit (4) IDD PO LM4925 Typical (3) (5) RL = 8, BTL, PO = 300mW, Figure 5, f = 1kHz 0.1 RL = 16, SE, PO = 20mW per channel, Figure 4, f = 1kHz 0.05 mA (max) 20Hz to 20kHz, A-weighted, Input Referred, Single Ended Output, Figure 4 10 VRMS RL = 16, Figure 4 58 dB VRIPPLE = 200mVP-P sine wave CBYPASS = 4.7F, RL = 8 f = 100Hz, BTL, Figure 5 70 dB VRIPPLE = 200mVP-P sine wave CBYPASS = 4.7F, RL = 16 f = 100Hz, SE, Figure 4 68 dB VIH Control Logic High 1.5V VDD 3.6V 0.7VDD VIL Control Logic Low 1.5V VDD 3.6V 0.3VDD V (max) 1VPP Reference, Ri = 20k, Rf = 50k 70 dB (min) Mute Attenuation (1) (2) (3) (4) (5) (6) V (min) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not ensure specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication of device performance. All voltages are measured with respect to the ground (GND) pins unless otherwise specified. Typicals are measured at 25C and represent the parametric norm. Datasheet min/max specification limits are specified by design, test, or statistical analysis. The quiescent power supply current depends on the offset voltage when a practical load is connected to the amplifier. Output power is measured at the device terminals. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 5 LM4925 SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 Electrical Characteristics VDD = 1.8V www.ti.com (1) (2) The following specifications apply for the circuit shown in Figure 4 for Single Ended Outputs (AV = 2.5V) and Figure 5 for BTL Outputs (AV-BTL = 2), unless otherwise specified. Limits apply for TA = 25C. Symbol Parameter Conditions IDD Quiescent Power Supply Current VIN = 0V, IO = 0A, RL = ISD Shutdown Current VSHUTDOWN = GND VOS Output Offset Voltage PO Output Power (6) THD+N Total Harmonic Distortion + Noise VNO Output Voltage Noise Crosstalk PSRR Power Supply Rejection Ratio LM4925 (5) Typical (3) Limit (4) Units (Limits) 0.9 1.6 0.05 1 mA (max) A (max) 2 10 mV (max) RL = 8, BTL, Figure 5, THD+N = 1%, f = 1kHz 120 90 mW (min) RL = 16, Figure 4, SE per Channel, THD+N = 1%, f = 1kHz 10 7 mW (min) 0.5 % (max) RL = 8, BTL, PO = 50mW, Figure 5, f = 1kHz 0.15 RL = 16, SE, PO = 5mW per channel, Figure 4, f = 1kHz 0.1 20Hz to 20kHz, A-weighted, Input Referred, Single Ended Output, Figure 4 10 VRMS RL = 16, Figure 4 58 dB VRIPPLE = 200mVP-P sine wave CBYPASS = 4.7F, RL = 8 f = 100Hz, BTL, Figure 5 70 dB VRIPPLE = 200mVP-P sine wave CBYPASS = 4.7F, RL = 16 f = 100Hz, SE, Figure 4 68 dB VIH Control Logic High 1.5V VDD 3.6V 0.7VDD VIL Control Logic Low 1.5V VDD 3.6V 0.3VDD V (max) 1VPP Reference, Ri = 20k, Rf = 50k 70 dB (min) Mute Attenuation (1) (2) (3) (4) (5) (6) 6 V (min) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not ensure specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication of device performance. All voltages are measured with respect to the ground (GND) pins unless otherwise specified. Typicals are measured at 25C and represent the parametric norm. Datasheet min/max specification limits are specified by design, test, or statistical analysis. The quiescent power supply current depends on the offset voltage when a practical load is connected to the amplifier. Output power is measured at the device terminals. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 LM4925 www.ti.com SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 Typical Performance Characteristics THD+N vs Frequency VDD = 3V, SE, RL = 16 PO = 20mW per channel 10 1 1 THD + N (%) THD + N (%) 10 THD+N vs Frequency VDD = 1.8V, SE, RL = 16 PO = 5mW per channel 0.1 0.1 0.01 0.01 100 1k 10k 100 FREQUENCY (Hz) 10 Figure 7. THD+N vs Frequency VDD = 1.8V, BTL, RL = 8 PO = 50mW THD+N vs Frequency VDD = 3V, BTL, RL = 8 PO = 300mW 10 1 THD + N (%) THD + N (%) 10k Figure 6. 1 0.1 0.1 0.01 0.01 0.001 0.001 100 1k 10k 100 FREQUENCY (Hz) 1k 10k FREQUENCY (Hz) Figure 8. Figure 9. THD+N vs Output Power VDD = 1.8V, SE, RL = 16 f = 1kHz, Both channels THD+N vs Output Power VDD = 3V, SE, RL = 16 f = 1kHz, Both channels 10 10 1 1 THD + N (%) THD + N (%) 1k FREQUENCY (Hz) 0.1 0.1 0.01 0.01 1 2 3 5 7 10 1 20 30 40 60 2 3 5 7 10 20 30 40 60 OUTPUT POWER (mW) OUTPUT POWER (mW) Figure 10. Figure 11. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 7 LM4925 SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) THD+N vs Output Power VDD = 3V, BTL, RL = 8 f = 1kHz 10 10 1 1 THD + N (%) THD + N (%) THD+N vs Output Power VDD = 1.8V, BTL, RL = 8 f = 1kHz 0.1 0.01 0.1 0.01 1 10 100 1 10 OUTPUT POWER (mW) OUTPUT POWER (mW) Figure 12. Figure 13. Output Noise vs Frequency Output Power vs Supply Voltage RL = 8, BTL, f = 1kHz 800 700 50 OUTPUT POWER (mW) OUTPUT NOISE LEVEL (PV) 100 20 10 5 2 600 500 THD+N = 10% 400 300 200 THD+N = 1% 100 1 0 2k 4k 6k 8k 10k 12k 14k 16k 18k 20k 1.6 FREQUENCY (Hz) 2.0 2.4 2.8 3.2 3.6 SUPPLY VOLTAGE (V) Figure 14. Figure 15. Output Power vs Supply Voltage RL = 16, SE, f = 1kHz Output Power vs Load Resistance VDD = 1.8V, BTL, f = 1kHz 200 80 POWER DISSIPATION (mW) 70 OUTPUT POWER (mW) 100 60 50 THD+N = 10% 40 30 20 THD+N = 1% 150 THD+N = 10% 100 THD+N = 1% 50 10 0 0 1.6 2.0 2.4 2.8 3.2 16 3.6 64 80 96 112 128 LOAD RESISTANCE (:) SUPPLY VOLTAGE (V) Figure 16. 8 32 48 Figure 17. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 LM4925 www.ti.com SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 Typical Performance Characteristics (continued) Output Power vs Load Resistance VDD = 3V, BTL, f = 1kHz 14 600 12 500 POWER DISSIPATION (mW) POWER DISSIPATION (mW) Output Power vs Load Resistance VDD = 1.8V, SE, f = 1kHz 10 THD+N = 10% 8 6 4 THD+N = 1% 2 0 THD+N = 10% 400 300 200 THD+N = 1% 100 0 16 32 48 64 80 96 112 128 16 32 48 64 80 96 112 128 144 LOAD RESISTANCE (:) Figure 18. Figure 19. Output Power vs Load Resistance VDD = 3V, SE, f = 1kHz Output Power vs Supply Voltage RL = 8, BTL, f = 1kHz 60 800 50 700 THD+N = 10% OUTPUT POWER (mW) POWER DISSIPATION (mW) LOAD RESISTANCE (:) THD+N = 10% 40 30 THD+N = 1% 20 500 400 300 200 THD+N = 1% 10 0 600 100 16 32 48 64 80 96 0 112 128 1.6 2.0 LOAD RESISTANCE (:) 2.4 2.8 3.2 3.6 SUPPLY VOLTAGE (V) Figure 20. Figure 21. Power Dissipation vs Output Power VDD = 1.8V, RL = 8, BTL, f = 1kHz Power Dissipation vs Output Power VDD = 1.8V, RL = 16, SE, f = 1kHz 90 250 POWER DISSIPATION (mW) POWER DISSIPATION (mW) 80 200 150 100 50 70 60 50 40 30 20 10 0 0 0 20 40 60 80 100 120 140 0 2 4 6 8 OUTPUT POWER (mW) OUTPUT POWER (mW) Figure 22. Figure 23. 10 12 Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 9 LM4925 SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) Power Dissipation vs Output Power VDD = 3V, RL = 8, BTL, f = 1kHz Power Dissipation vs Output Power VDD = 3V, RL = 16, SE, f = 1kHz 120 POWER DISSIPATION (mW) POWER DISSIPATION (mW) 250 200 150 100 50 0 100 80 60 40 20 0 0 100 200 300 400 0 500 12 16 20 24 28 32 36 40 Figure 25. Power Supply Rejection vs Frequency VDD = 1.8V, RL = 8, BTL VRIPPLE = 200mVp-p, AV-BTL = 2V/V Power Supply Rejection vs Frequency VDD = 1.8V, RL = 16, SE VRIPPLE = 200mVp-p, AV = 2.5V/V 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 20 200 2k 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 20 20k 200 2k 20k FREQUENCY (Hz) Figure 26. Figure 27. Power Supply Rejection vs Frequency VDD = 3V, RL = 8, BTL VRIPPLE = 200mVp-p, AV-BTL = 2V/V Power Supply Rejection vs Frequency VDD = 3V, RL = 16, SE VRIPPLE = 200mVp-p, AV = 2.5V/V 0 POWER SUPPLY REJECTION RATIO (dB) POWER SUPPLY REJECTION RATIO (dB) 8 OUTPUT POWER (mW) FREQUENCY (Hz) -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 20 200 2k 20k FREQUENCY (Hz) 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 20 200 2k 20k FREQUENCY (Hz) Figure 28. 10 4 Figure 24. POWER SUPPLY REJECTION RATIO (dB) POWER SUPPLY REJECTION RATIO (dB) OUTPUT POWER (mW) Figure 29. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 LM4925 www.ti.com SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 APPLICATION INFORMATION BRIDGE (BTL) CONFIGURATION EXPLANATION The LM4925 is a stereo audio power amplifier capable of operating in bridged (BTL) mode. As shown in Figure 5, the LM4925 has two internal operational amplifiers. The first amplifier's gain is externally configurable, while the second amplifier should be externally fixed in a unity-gain, inverting configuration. The closed-loop gain of the first amplifier is set by selecting the ratio of Rf to Ri while the second amplifier's gain is fixed by the two external 20k resistors. Figure 5 shows that the output of amplifier one serves as the input to amplifier two which results in both amplifiers producing signals identical in magnitude, but out of phase by 180. Consequently, the differential gain for the IC is AVD = 2 * (Rf / Ri) (1) By driving the load differentially through outputs VoA and VoB, an amplifier configuration commonly referred to as "bridged mode" is established. Bridged mode operation is different from the classical single-ended amplifier configuration where one side of the load is connected to ground. A bridge amplifier design has a few distinct advantages over the single-ended configuration, as it provides differential drive to the load, thus doubling output swing for a specified supply voltage. Four times the output power is possible as compared to a single-ended amplifier under the same conditions. This increase in attainable output power assumes that the amplifier is not current limited or clipped. In order to choose an amplifier's closed-loop gain without causing excessive clipping, please refer to the AUDIO POWER AMPLIFIER DESIGN section. A bridge configuration, such as the one used in LM4925, also creates a second advantage over single-ended amplifiers. Since the differential outputs, VoA and VoB, are biased at half-supply, no net DC voltage exists across the load. This eliminates the need for an output coupling capacitor which is required in a single supply, single-ended amplifier configuration. MODE SELECT DETAIL The LM4925 can be configured for either single ended (see Figure 4) or BTL mode (see Figure 5). When the SE/BTL pin has a logic high (VDD) applied to it, the LM4925 is in BTL mode. If a logic low (GND) is applied to SE/BTL, the LM4925 operates in single-ended mode. The slew rate of VDD must be greater than 2.5V/ms to ensure reliable Power on reset (POR). The circuit shown in Figure 30 presents an applications solution to the problem of using different supply voltages with different turn-on times in a system with the LM4925. This circuit shows the LM4925 with a 25-50k. Pull-up resistor connected from the shutdown pin to VDD. The shutdown pin of the LM4925 is also being driven by an open drain output of an external microcontroller on a separate supply. This circuit ensures that shutdown is disabled when powering up the LM4925 by either allowing shutdown to be high before the LM4925 powers on (the microcontroller powers up first) or allows shutdown to ramp up with VDD (the LM4925 powers up first). This will ensure the LM4925 powers up properly and enters the correct mode of operation (BTL or SE). Please note that the SE/BTL pin should be tied to GND for single-ended (SE) mode, and to Vdd for BTL mode. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 11 LM4925 SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 www.ti.com 3.3V 20k 5V 25k to 50k 10 1 Controller 0.47 PF IN A VDD VoA 9 20k MOSFET N 100 PF 2 SPEAKER SD LM4925 3 4 5 0.47 PF MUTE SE/BT 8 BYP IN B 20k 4.7 mF GND 6 VoB 7 100 PF SPEAKER 20k Figure 30. Recommended Circuit for Different Supply Turn-On Timing POWER DISSIPATION Power dissipation is a major concern when designing a successful amplifier, whether the amplifier is bridged (BTL) or single-ended. A direct consequence of the increased power delivered to the load by a bridge amplifier is an increase in internal power dissipation. Since the LM4925 has two operational amplifiers in one package, the maximum internal power dissipation in BTL mode is 4 times that of a single-ended amplifier. The maximum power dissipation for a given application can be derived from the power dissipation graphs or from Equation 2. PDMAX = 4 * (VDD) 2 / (22RL) (2) When operating in single ended mode, Equation 3 states the maximum power dissipation point for a singleended amplifier operating at a given supply voltage and driving a specified output load. PDMAX = (VDD) 2 / (22RL) (3) Since the LM4925 has two operational amplifiers in one package, the maximum internal power dissipation point is twice that of the number that results from Equation 3. The maximum power dissipation point obtained from either Equation 2 or Equation 3 must not be greater than the power dissipation that results from Equation 4: PDMAX = (TJMAX - TA) / JA (4) For package DGS, JA = 175C/W. TJMAX = 150C for the LM4925. Depending on the ambient temperature, TA, of the system surroundings, Equation 4 can be used to find the maximum internal power dissipation supported by the IC packaging. If the result of Equation 2 or Equation 3 is greater than that of Equation 4, then either the supply voltage must be decreased, the load impedance increased or TA reduced. For the typical application of a 3.0V power supply, with an 16 load, the maximum ambient temperature possible without violating the maximum junction temperature is approximately 129C provided that device operation is around the maximum power dissipation point. Thus, for typical applications, power dissipation is not an issue. Power dissipation is a function of output power and thus, if typical operation is not around the maximum power dissipation point, the ambient temperature may be increased accordingly. Refer to the Typical Performance Characteristics curves for power dissipation information for lower output powers. POWER SUPPLY BYPASSING As with any amplifier, proper supply bypassing is important for low noise performance and high power supply rejection. The capacitor location on the power supply pins should be as close to the device as possible. Typical applications employ a battery (or 3.0V regulator) with 10F tantalum or electrolytic capacitor and a ceramic bypass capacitor that aid in supply stability. This does not eliminate the need for bypassing the supply nodes of the LM4925. A bypass capacitor value in the range of 0.1F to 4.7F is recommended. 12 Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 LM4925 www.ti.com SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 MICRO POWER SHUTDOWN The voltage applied to the SHUTDOWN pin controls the LM4925's shutdown function. Activate micro-power shutdown by applying a logic-low voltage to the SHUTDOWN pin. When active, the LM4925's micro-power shutdown feature turns off the amplifier's bias circuitry, reducing the supply current. A voltage that is higher than ground may increase the shutdown current. There are a few ways to control the micro-power shutdown. These include using a single-pole, single-throw switch, a microprocessor, or a microcontroller. When using a switch, connect an external 100k pull-up resistor between the SHUTDOWN pin and VDD. Connect the switch between the SHUTDOWN pin and ground. Select normal amplifier operation by opening the switch. Closing the switch connects the SHUTDOWN pin to ground, activating micro-power shutdown. The switch and resistor ensure that the SHUTDOWN pin will not float. This prevents unwanted state changes. In a system with a microprocessor or microcontroller, use a digital output to apply the control voltage to the SHUTDOWN pin. Driving the SHUTDOWN pin with active circuitry eliminates the pull-up resistor. Shutdown enable/disable times are controlled by a combination of Cbypass and VDD. Larger values of Cbypass results in longer turn on/off times from Shutdown. Longer shutdown times also improve the LM4925's resistance to click and pop upon entering or returning from shutdown. For a 3.0V supply and Cbypass = 4.7F, the LM4925 requires about 2 seconds to enter or return from shutdown. This longer shutdown time enables the LM4925 to have virtually zero pop and click transients upon entering or release from shutdown. Smaller values of Cbypass will decrease turn-on time, but at the cost of increased pop and click and reduced PSRR. When the LM4925 is in shutdown, the outputs become very low impedance (less than 5 to GND). MUTE The LM4925 also features a mute function that enables extremely fast turn-on/turn-off with a minimum of output pop and click. The mute function leaves the outputs at their bias level, thus resulting in higher power consumption than shutdown mode, but also provides much faster turn on/off times. Providing a logic low signal on the MUTE pin enables mute mode. Threshold voltages and activation techniques match those given for the shutdown function as well. PROPER SELECTION OF EXTERNAL COMPONENTS Proper selection of external components in applications using integrated power amplifiers is critical to optimize device and system performance. While the LM4925 is tolerant of external component combinations, consideration to component values must be used to maximize overall system quality. The LM4925 is unity-gain stable that gives the designer maximum system flexibility. The LM4925 should be used in low gain configurations to minimize THD+N values, and maximize the signal to noise ratio. Low gain configurations require large input signals to obtain a given output power. Input signals equal to or greater than 1Vrms are available from sources such as audio codecs. Very large values should not be used for the gain-setting resistors. Values for Ri and Rf should be less than 1M. Please refer to the section, AUDIO POWER AMPLIFIER DESIGN, for a more complete explanation of proper gain selection. Besides gain, one of the major considerations is the closed-loop bandwidth of the amplifier. To a large extent, the bandwidth is dictated by the choice of external components shown in Figure 4 and Figure 5. The input coupling capacitor, Ci, forms a first order high pass filter that limits low frequency response. This value should be chosen based on needed frequency response and turn-on time. SELECTION OF INPUT CAPACITOR SIZE Amplifying the lowest audio frequencies requires a high value input coupling capacitor, Ci. A high value capacitor can be expensive and may compromise space efficiency in portable designs. In many cases, however, the headphones used in portable systems have little ability to reproduce signals below 60Hz. Applications using headphones with this limited frequency response reap little improvement by using a high value input capacitor. In addition to system cost and size, turn on time is affected by the size of the input coupling capacitor Ci. A larger input coupling capacitor requires more charge to reach its quiescent DC voltage. This charge comes from the output via the feedback. Thus, by minimizing the capacitor size based on necessary low frequency response, turn-on time can be minimized. A small value of Ci (in the range of 0.1F to 0.47F), is recommended. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 13 LM4925 SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 www.ti.com AUDIO POWER AMPLIFIER DESIGN A 25mW/32 Audio Amplifier Given: Power Output 10mWrms Load Impedance 16 Input Level 0.4Vrms Input Impedance 20k A designer must first choose a mode of operation (SE or BTL) and determine the minimum supply rail to obtain the specified output power. By extrapolating from the Output Power vs. Supply Voltage graphs in the Typical Performance Characteristics section, the supply rail can be easily found. 3.0V is a standard voltage in most applications, it is chosen for the supply rail. Extra supply voltage creates headroom that allows the LM4925 to reproduce peak in excess of 10mW without producing audible distortion. At this time, the designer must make sure that the power supply choice along with the output impedance does not violate the conditions explained in the POWER DISSIPATION section. Once the power dissipation equations have been addressed, the required gain can be determined from Equation 5. (5) From Equation 5, the minimum AV is 1; use AV = 1. Since the desired input impedance is 20k, and with a AV gain of 1, a ratio of 1:1 results from Equation 1 for Rf to R. The values are chosen with Ri = 20k and Rf = 20k. The final design step is to address the bandwidth requirements which must be stated as a pair of -3dB frequency points. Five times away from a -3dB point is 0.17dB down from passband response which is better than the required 0.25dB specified. fL = 100Hz/5 = 20Hz fH = 20kHz * 5 = 100kHz As stated in the PROPER SELECTION OF EXTERNAL COMPONENTS section, Ri in conjunction with Ci creates a Ci 1 / (2 * 20k * 20Hz) = 0.397F; use 0.39F. The high frequency pole is determined by the product of the desired frequency pole, fH, and the differential gain, AV. With an AVV = 1 and fH = 100kHz, the resulting GBWP = 100kHz which is much smaller than the LM4925GBWP of 3MHz. This example displays that if a designer has a need to design an amplifier with higher differential gain, the LM4925can still be used without running into bandwidth limitations. 14 Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 LM4925 www.ti.com SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 LM4925 BOARD ARTWORK Figure 31. Composite View Figure 32. Silk Screen Figure 33. Top Layer Figure 34. Bottom Layer Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 15 LM4925 SNAS273A - FEBRUARY 2005 - REVISED APRIL 2013 www.ti.com REVISION HISTORY Changes from Original (April 2013) to Revision A * 16 Page Changed layout of National Data Sheet to TI format .......................................................................................................... 15 Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4925 PACKAGE OPTION ADDENDUM www.ti.com 6-Apr-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish (2) MSL Peak Temp Op Temp (C) Top-Side Markings (3) (4) LM4925MM/NOPB ACTIVE VSSOP DGS 10 1000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM GB8 LM4925SD/NOPB ACTIVE WSON DSC 10 1000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM L4925 (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) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) Multiple Top-Side Markings will be inside parentheses. Only one Top-Side Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Top-Side Marking for that device. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 1 Samples PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM4925MM/NOPB VSSOP DGS 10 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1 LM4925SD/NOPB WSON DSC 10 1000 178.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM4925MM/NOPB VSSOP DGS 10 1000 210.0 185.0 35.0 LM4925SD/NOPB WSON DSC 10 1000 210.0 185.0 35.0 Pack Materials-Page 2 MECHANICAL DATA DSC0010A SDA10A (Rev A) www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All semiconductor products (also referred to herein as "components") are sold subject to TI's terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI's terms and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily performed. TI assumes no liability for applications assistance or the design of Buyers' products. Buyers are responsible for their products and applications using TI components. To minimize the risks associated with Buyers' products and applications, Buyers should provide adequate design and operating safeguards. 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 relating to any combination, machine, or process in which TI components or services are used. Information published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use of any TI components in safety-critical applications. In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI's goal is to help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and requirements. Nonetheless, such components are subject to these terms. No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties have executed a special agreement specifically governing such use. Only those TI components which TI has specifically designated as military grade or "enhanced plastic" are designed and intended for use in military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of non-designated products, TI will not be responsible for any failure to meet ISO/TS16949. Products Applications Audio www.ti.com/audio Automotive and Transportation www.ti.com/automotive Amplifiers amplifier.ti.com Communications and Telecom www.ti.com/communications Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers DLP(R) Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps DSP dsp.ti.com Energy and Lighting www.ti.com/energy Clocks and Timers www.ti.com/clocks Industrial www.ti.com/industrial Interface interface.ti.com Medical www.ti.com/medical Logic logic.ti.com Security www.ti.com/security Power Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video RFID www.ti-rfid.com OMAP Applications Processors www.ti.com/omap TI E2E Community e2e.ti.com Wireless Connectivity www.ti.com/wirelessconnectivity Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright (c) 2013, Texas Instruments Incorporated