LM4805 www.ti.com SNAS289B - MAY 2005 - REVISED APRIL 2013 LM4805 BoomerTM Audio Power Amplifier Series Low Voltage High Power Audio Power Amplifier Check for Samples: LM4805 FEATURES DESCRIPTION * The LM4805 is a boosted audio power amplifier designed for driving 8ohm speakers in portable applications. It delivers at least 1W continuous power to an 8 load from any input voltage between 3V and 4.6V with less than 2% THD+N. 1 23 * * * * Pop & Click Circuitry Eliminates Noise During Turn-On and Turn-Off Transitions Low, 2A (Max) Shutdown Current Low, 14mA (Typ) Quiescent Current Unity-Gain Stable External Gain Configuration Capability Boomer audio power amplifiers were designed specifically to provide high quality output power with a minimal amount of external components. The LM4805 does not require bootstrap capacitors, or snubber circuits. Therefore it is ideally suited for portable applications requiring high power and minimal size. APPLICATIONS * * Cellphone PTT (Push To Talk) Mobile Phones The LM4805 features a low-power consumption shutdown mode along with an internal thermal shutdown protection mechanism and short circuit protection. KEY SPECIFICATIONS * * * Quiescent Power Supply Current (VDD = 3V), 14mA (Typ) Output Power (VDD = 3.0V, RL = 8, THD+N = 2%), 1W (Typ) Shutdown Current, 2A (Max) The LM4805 contains advanced pop & click circuitry that eliminates noises which would otherwise occur during turn-on and turn-off transitions. The LM4805 is unity-gain stable and can be configured by external gain-setting resistors. NC NC V1 Vo1 NC NC IN- Connection Diagram 28 27 26 25 24 23 22 NC 1 21 IN+ NC 2 20 GND NC 3 19 Bypass VDD 4 18 Shutdown 2 15 NC 8 9 10 11 12 13 14 NC 7 NC GND SW NC GND Vo2 16 NC 17 NC 5 6 FB NC Shutdown 1 Figure 1. LM4805LQ (5x5) (Top View) See Package Number NJB0028A 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 LM4805 SNAS289B - MAY 2005 - REVISED APRIL 2013 www.ti.com Typical Application D1 L1 10 PH Cs1 4.7 PF 4 VDD 7 12 6 S/D 18 19 CB 1.0 PF 21 Cf1 470 pF 11 Co 4.7 PF R1 51.1k SW VDD Battery V1 = VFB (1 + R1/R2) GND1 FB 8 R2 15k GND2 S/D1 V1 S/D2 Bypass GND3 +IN VO2 26 20 Cs2 4.7 PF 17 RL 8: 20k Audio In 0.1 PF Ci 22 -IN VO1 25 Ri Rf 200k 82 pF Cf2 * * Cf2 is optional. Figure 2. Typical Audio Amplifier Application 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. 2 Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 LM4805 www.ti.com SNAS289B - MAY 2005 - REVISED APRIL 2013 Absolute Maximum Ratings (1) (2) (3) Supply Voltage (VDD) 6.5V Supply Voltage (V1) 6.5V -65C to +150C Storage Temperature -0.3V to VDD + 0.3V Input Voltage (4) Internally limited ESD Susceptibility (5) 2000V ESD Susceptibility (6) 200V Power Dissipation Junction Temperature Thermal Resistance 125C JA (WQFN) 59C/W See AN-1187 Leadless Leadframe Packaging (WQFN) (SNOA401). (1) (2) (3) (4) (5) (6) All voltages are measured with respect to the GND pin, unless otherwise specified. 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 must be derated at elevated temperatures and is dictated by TJMAX, JA, and the ambient temperature, TA. The maximum allowable power dissipation is PDMAX = (TJMAX - TA) / JA or the given in Absolute Maximum Ratings, whichever is lower. Human body model, 100pF discharged through a 1.5k resistor. Machine Model, 220pF-240pF discharged through all pins. Operating Ratings Temperature Range TMIN TA TMAX -40C TA +85C 2.7V VDD 4.6V Supply Voltage (VDD) 2.7V V1 6.1V Supply Voltage (V1) Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 3 LM4805 SNAS289B - MAY 2005 - REVISED APRIL 2013 www.ti.com Electrical Characteristics VDD = 4.2V (1) (2) The following specifications apply for VDD = 4.2V, AV-BTL = 26dB, RL = 8, CB = 1.0F, R1 = 51.1k, R2 = 15k unless otherwise specified. Limits apply for TA = 25C. See Figure 2. Symbol Parameter Conditions LM4805 Typical (3) Limit (4) (5) Units (Limits) IDD Quiescent Power Supply Current VIN = 0, RLOAD = 10 23 mA (max) ISD Shutdown Current VSHUTDOWN = GND (6) (7) 0.1 2 A (max) VSDIH Shutdown Voltage Input High S/D1 and S/D2 1.5 V (min) VSDIL Shutdown Voltage Input Low S/D1 and S/D2 0.4 V (max) TWU Wake-up Time CB = 1.0F 80 110 msec (max) VOS Output Offset Voltage 5 40 mV (max) TSD Thermal Shutdown Temperature 125 C (min) POUT Output Power THD = 1% (max), f = 1kHz, Mono BTL 1.2 0.9 W (min) THD+N Total Harmomic Distortion + Noise PO = 500mW, f = 1kHz 0.2 0.5 % (max) OS Output Noise A-Weighted Filter, VIN = 0V 105 V PSRR Power Supply Rejection Ratio VRIPPLE = 200mVp-p, f = 100Hz, inputs terminated 66 dB VFB Feedback Pin Reference Voltage See (8) 1.23 V (1) (2) (3) (4) (5) (6) (7) (8) 4 All voltages are measured with respect to the GND pin, unless otherwise specified. 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. Typicals are measured at 25C and represent the parametric norm. Limits are specified to Texas Instruments' AOQL (Average Outgoing Quality Level). Datasheet min/max specification limits are specified by design, test, or statistical analysis. Shutdown current is measured at an ambient temperature of 25C. The Shutdown pin should be driven as close as possible to GND for minimum shutdown current. Shutdown current is measured with components R1 and R2 removed. Feedback pin reference voltage is measured with the Audio Amplifier's V1 (pin 26) floating and no addition load connected to the cathode of D1 (see Figure 2). Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 LM4805 www.ti.com SNAS289B - MAY 2005 - REVISED APRIL 2013 Electrical Characteristics VDD = 3.0V (1) (2) The following specifications apply for VDD = 3.0V, AV-BTL = 26dB, RL = 8, CB = 1.0F, R1 = 51.1k, R2 = 15k unless otherwise specified. Limits apply for TA = 25C. Symbol Parameter Conditions LM4805 Typical (3) Limit (4) (5) Units (Limits) IDD Quiescent Power Supply Current VDD = 3.2V, VIN = 0, RLOAD = 14 27 mA (max) ISD Shutdown Current VSHUTDOWN = GND (6) (7) 0.1 2 A (max) VSDIH Shutdown Voltage Input High S/D1 and S/D2 1.5 V (min) VSDIL Shutdown Voltage Input Low S/D1 and S/D2 0.4 V (max) TWU Wake-up Time CB = 1.0F 80 110 msec (max) VOS Output Offset Voltage 5 40 mV (max) TSD Thermal Shutdown Temperature 125 C (min)) POUT Output Power THD = 2% (max), f = 1kHz, Mono BTL 1 0.85 W (min) THD+N Total Harmomic Distortion + Noise PO = 500mW, fIN = 1kHz 0.25 0.55 % (max) OS Output Noise A-Weighted Filter, VIN = 0V 105 V PSRR Power Supply Rejection Ratio VRIPPLE = 200mVp-p, f = 100Hz 66 dB (min) VFB Feedback Pin Reference Voltage See (8) (1) (2) (3) (4) (5) (6) (7) (8) 1.23 1.205 1.255 V (max) V (min) All voltages are measured with respect to the GND pin, unless otherwise specified. 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. Typicals are measured at 25C and represent the parametric norm. Limits are specified to Texas Instruments' AOQL (Average Outgoing Quality Level). Datasheet min/max specification limits are specified by design, test, or statistical analysis. Shutdown current is measured at an ambient temperature of 25C. The Shutdown pin should be driven as close as possible to GND for minimum shutdown current. Shutdown current is measured with components R1 and R2 removed. Feedback pin reference voltage is measured with the Audio Amplifier's V1 (pin 26) floating and no addition load connected to the cathode of D1 (see Figure 2). Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 5 LM4805 SNAS289B - MAY 2005 - REVISED APRIL 2013 www.ti.com Typical Performance Characteristics 10 THD+N vs Frequency VDD = 3V, AV = 6dB, RL = 8 10 1 THD + N (%) THD + N (%) 1 0.1 0.01 10 100 1k 20k 20 1k 20k FREQUENCY (Hz) Figure 3. Figure 4. THD+N vs Frequency VDD = 3V, AV = 26dB, RL = 8 THD+N vs Frequency VDD = 3V, AV = 26dB, RL = 16 10 1 THD + N (%) THD + N (%) 100 FREQUENCY (Hz) 1 0.1 0.01 0.1 0.01 20 10 100 1k 20k 20 100 1k FREQUENCY (Hz) FREQUENCY (Hz) Figure 5. Figure 6. THD+N vs Frequency VDD = 4.2V, AV = 6dB, RL = 8 10 20k THD+N vs Frequency VDD = 4.2V, AV = 6dB, RL = 16 1 THD + N (%) 1 THD + N (%) 0.1 0.01 20 0.1 0.01 0.1 0.01 20 6 THD+N vs Frequency VDD = 3V, AV = 6dB, RL = 16 100 1k 20k 20 100 1k FREQUENCY (Hz) FREQUENCY (Hz) Figure 7. Figure 8. Submit Documentation Feedback 20k Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 LM4805 www.ti.com SNAS289B - MAY 2005 - REVISED APRIL 2013 Typical Performance Characteristics (continued) 10 THD+N vs Frequency VDD = 4.2V, AV = 26dB, RL = 8 10 1 THD + N (%) THD + N (%) 1 0.1 0.01 10 100 1k 20k 20 10 20k Figure 9. Figure 10. THD+N vs Output Power VDD = 3V, AV = 6dB, RL = 8 THD+N vs Output Power VDD = 3V, AV = 6dB, RL = 16 10 THD + N (%) 1 0.1 0.01 50 100 1000 2000 200 500 OUTPUT POWER (mW) 100 1000 2000 200 500 OUTPUT POWER (mW) Figure 11. Figure 12. THD+N vs Output Power VDD = 3V, AV = 26dB, RL = 8 THD+N vs Output Power VDD = 3V, AV = 26dB, RL = 16 10 1 THD + N (%) 1 0.1 0.01 50 1k FREQUENCY (Hz) 0.1 0.01 50 100 FREQUENCY (Hz) 1 THD + N (%) 0.1 0.01 20 THD + N (%) THD+N vs Frequency VDD = 4.2V, AV = 26dB, RL = 16 100 200 500 1000 2000 OUTPUT POWER (mW) Figure 13. 0.1 0.01 50 100 200 500 1000 2000 OUTPUT POWER (mW) Figure 14. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 7 LM4805 SNAS289B - MAY 2005 - REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) THD+N vs Output Power VDD = 4.2V, AV = 6dB, RL = 8 10 10 1 THD + N (%) THD + N (%) 1 0.1 0.01 50 10 0.1 0.01 50 100 200 500 1000 2000 OUTPUT POWER (mW) 100 200 500 1000 2000 OUTPUT POWER (mW) Figure 15. Figure 16. THD+N vs Output Power VDD = 4.2V, AV = 26dB, RL = 8 THD+N vs Output Power VDD = 4.2V, AV = 26dB, RL = 16 10 1 THD + N (%) 1 THD + N (%) THD+N vs Output Power VDD = 4.2V, AV = 6dB, RL = 16 0.1 0.01 50 0.1 0.01 50 100 1000 2000 200 500 OUTPUT POWER (mW) 100 1000 2000 200 500 OUTPUT POWER (mW) Figure 17. Figure 18. Power Dissipation vs Output Power VDD = 3V, RL = 8, f = 1kHz Supply Current vs Supply Voltage 1400 18 POWER DISSIPATION (mW) SUPPLY CURRENT (mA) 16 14 12 10 8 6 4 2 0 2.5 8 3.0 3.5 4.0 4.5 5.0 1200 1000 800 600 400 200 0 0 200 400 600 800 1000 1200 1400 SUPPLY VOLTAGE (V) OUTPUT POWER (mW) Figure 19. Figure 20. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 LM4805 www.ti.com SNAS289B - MAY 2005 - REVISED APRIL 2013 Typical Performance Characteristics (continued) Power Dissipation vs Output Power VDD = 3V, RL = 16, f = 1kHz Power Dissipation vs Output Power VDD = 4.2V, RL = 8, f = 1kHz 800 1200 POWER DISSIPATION (mW) POWER DISSIPATION (mW) 700 600 500 400 300 200 1000 100 0 0 400 200 600 800 1000 600 400 200 0 1200 0 200 600 800 1000 1200 OUTPUT POWER (mW) Figure 21. Figure 22. Power Dissipation vs Output Power VDD = 4.2V, RL = 16, f = 1kHz Output Power vsLoad Resistance VDD = 3V 1400 1200 OUTPUT POWER (mW) 500 400 300 200 100 0 THD+N = 10% 1000 800 600 THD+N = 1% 400 200 0 400 200 0 800 1000 1200 1400 600 8 12 OUTPUT POWER (mW) 24 20 28 32 36 Figure 24. Output Power vs Load Resistance VDD = 4.2V Output Power vs Supply Voltage RL = 8, f = 1kHz 1400 2000 THD+N = 10% 1200 OUTPUT POWER (mW) THD+N = 10% 1000 800 600 16 LOAD RESISTANCE (:) Figure 23. OUTPUT POWER (mW) 400 OUTPUT POWER (mW) 600 POWER DISSIPATION (mW) 800 THD+N = 1% 400 1500 1000 THD+N = 1% 500 200 0 8 12 16 20 24 28 32 0 36 LOAD RESISTANCE (:) 2.8 3.2 3.6 4.0 4.4 5.0 SUPPLY VOLTAGE (V) Figure 25. Figure 26. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 9 LM4805 SNAS289B - MAY 2005 - REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) Output Power vs Supply Voltage RL = 16, f = 1kHz 1200 0 THD+N = 10% -20 800 600 PSRR (dB) OUTPUT POWER (mW) 1000 THD+N = 1% 400 0 0 -40 -60 -80 200 3.2 2.8 4.0 3.6 4.4 -100 20 5.0 Figure 27. Figure 28. PSRR vs FREQUENCY VDD = 3V, AV = 26dB Vripple = 200mVP-P PSRR vs FREQUENCY VDD = 4.2V, AV = 6dB Vripple = 200mVP-P 0 -20 -40 -40 -60 -80 0 20k 5k FREQUENCY (Hz) -20 -100 20 1k 100 SUPPLY VOLTAGE (V) PSRR (dB) PSRR (dB) PSRR vs FREQUENCY VDD = 3V, AV = 6dB Vripple = 200mVP-P -60 -80 100 1k 5k -100 20 20k 1k 100 FREQUENCY (Hz) Figure 29. Figure 30. PSRR vs FREQUENCY VDD = 4.2V, AV = 26dB Vripple = 200mVP-P 20k 5k FREQUENCY (Hz) Load Current vs VDD 1200 V1 = 5.0V LOAD CURRENT (mA) PSRR (dB) -20 -40 -60 1000 V1 = 5.8V 800 V1 = 6.1V 600 400 -80 200 -100 20 100 1k 5k 20k 0 0 1 2 3 4 5 6 FREQUENCY (Hz) VDD (V) Figure 31. 10 Figure 32. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 LM4805 www.ti.com SNAS289B - MAY 2005 - REVISED APRIL 2013 Typical Performance Characteristics (continued) Amplifier Frequency Response vs Input Capacitor Size Amplifier Open Loop vs Frequency Respose Figure 33. Figure 34. Switch Current Limit vs Duty Cycle - "X" Oscillator Frequency vs Temperature - "X" 3000 SW CURRENT LIMIT (mA) 2500 OSCILLATOR FREQUENCY (MHz) 1.58 VIN = 5V 2000 VIN = 3.3V 1500 1000 VIN = 2.7V 500 VIN = 3V 0 20 30 40 50 60 70 80 90 1.54 1.52 VIN = 3.3V 1.5 1.48 1.46 1.44 1.42 1.4 -50 100 VIN = 5V 1.56 -25 50 75 100 125 150 Figure 36. Feedback Voltage vs Temperature Feedback Bias Current vs Temperature 0.09 1.23 0.08 FEEDBACK BIAS CURRENT (PA) FEEDBACK VOLTAGE (V) 25 Figure 35. 1.231 1.229 1.228 1.227 1.226 1.225 1.224 1.223 1.222 -40 0 TEMPERATURE (oC) DUTY CYCLE (%) = [1 - EFF*(VIN / VOUT)] -25 0 25 50 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 -50 75 100 125 -25 0 25 50 75 100 125 150 TEMPERATURE (oC) TEMPERATURE (oC) Figure 37. Figure 38. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 11 LM4805 SNAS289B - MAY 2005 - REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) RDS (ON) vs Temperature 93 0.5 92.9 0.45 0.4 92.8 Vin = 3.3V 0.35 92.7 92.6 RDS(ON) (:) MAX DUTY CYCLE (%) Maximum Duty Cycle vs Temperature - "X" VIN = 5V 92.5 92.4 0.3 Vin = 5V 0.25 0.2 0.15 VIN = 3.3V 92.3 0.1 92.2 0.05 0 92.1 -50 -25 0 25 50 -40 75 100 125 150 -25 0 25 50 75 100 125 TEMPERATURE (oC) o TEMPERATURE ( C) Figure 39. Figure 40. RDS (ON) vs VDD 350 300 RDS_ON (m:) 250 200 150 100 50 0 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 VIN (V) Figure 41. 12 Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 LM4805 www.ti.com SNAS289B - MAY 2005 - REVISED APRIL 2013 APPLICATION INFORMATION BRIDGE CONFIGURATION EXPLANATION The Audio Amplifier portion of the LM4805 has two internal amplifiers allowing different amplifier configurations. The first amplifier's gain is externally configurable, whereas the second amplifier is internally 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 internal 20k resistors. Figure 2 shows that the output of amplifier one serves as the input to amplifier two. This results in both amplifiers producing signals identical in magnitude, but out of phase by 180. Consequently, the differential gain for the Audio Amplifier is AVD = 2 *(Rf/Ri) (1) By driving the load differentially through outputs VO1 and VO2, an amplifier configuration commonly referred to as "bridged mode" is established. Bridged mode operation is different from the classic 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. It provides differential drive to the load, thus doubling the 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 closedloop gain without causing excessive clipping, please refer to the Audio Power Amplifier Design section. The bridge configuration also creates a second advantage over single-ended amplifiers. Since the differential outputs, VO1 and VO2, 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. Without an output coupling capacitor, the half-supply bias across the load would result in both increased internal IC power dissipation and also possible loudspeaker damage. AMPLIFIER POWER DISSIPATION Power dissipation is a major concern when designing a successful amplifier, whether the amplifier is bridged 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 amplifier portion of the LM4805 has two operational amplifiers, the maximum internal power dissipation is 4 times that of a single-ended amplifier. The maximum power dissipation for a given BTL application can be derived from Equation 2. PDMAX(AMP) = 4(VDD)2 / (22RL) (2) BOOST CONVERTER POWER DISSIPATION At higher duty cycles, the increased ON-time of the switch FET means the maximum output current will be determined by power dissipation within the LM2731 FET switch. The switch power dissipation from ON-time conduction is calculated by Equation 3. PDMAX(SWITCH) = DC x IIND(AVE)2 x RDS(ON) where * DC is the duty cycle (3) There will be some switching losses as well, so some derating needs to be applied when calculating IC power dissipation. TOTAL POWER DISSIPATION The total power dissipation for the LM4805 can be calculated by adding Equation 2 and Equation 3 together to establish Equation 4: PDMAX(TOTAL) = [4*(VDD)2/22RL] + [DC x IIND(AVE)2 x RDS(ON)] (4) The result from Equation 4 must not be greater than the power dissipation that results from Equation 5: PDMAX = (TJMAX - TA) / JA (5) Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 13 LM4805 SNAS289B - MAY 2005 - REVISED APRIL 2013 www.ti.com For the NJB0028A, JA = 59C/W. TJMAX = 125C for the LM4805. Depending on the ambient temperature, TA, of the system surroundings, Equation 5 can be used to find the maximum internal power dissipation supported by the IC packaging. If the result of Equation 4 is greater than that of Equation 4, then either the supply voltage must be increased, the load impedance increased or TA reduced. For the typical application of a 3V power supply, with V1 set to 5.5V and an 8 load, the maximum ambient temperature possible without violating the maximum junction temperature is approximately 111C 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 levels. WQFN PACKAGE PCB MOUNTING CONSIDERATIONS The LM4805's exposed-DAP (die attach paddle) package (WQFN) provides a low thermal resistance between the die and the PCB to which the part is mounted and soldered. The low thermal resistance allows rapid heat transfer from the die to the surrounding PCB copper traces, ground plane, and surrounding air. The WQFN package should have its DAP soldered to a copper pad on the PCB. The DAP's PCB copper pad may be connected to a large plane of continuous unbroken copper. This plane forms a thermal mass, heat sink, and radiation area. Further detailed and specific information concerning PCB layout, fabrication, and mounting an WQFN package is found in Texas Instruments' Package Engineering Group under application note AN1187. SHUTDOWN FUNCTION In many applications, a microcontroller or microprocessor output is used to control the shutdown circuitry to provide a quick, smooth transition into shutdown. Another solution is to use a single-pole, single-throw switch, and a pull-up resistor. One terminal of the switch is connected to GND. The other side is connected to the two shutdown pins and the terminal of the pull-up resistor. The remaining resistance terminal is connected to VDD. If the switch is open, then the external pull-up resistor connected to VDD will enable the LM4805. This scheme ensures that the shutdown pins will not float thus preventing unwanted state changes. PROPER SELECTION OF EXTERNAL COMPONENTS Proper selection of external components in applications using integrated power amplifiers, and switching boost converters, is critical for optimizing device and system performance. Consideration to component values must be used to maximize overall system quality. The best capacitors for use with the switching converter portion of the LM4805 are multi-layer ceramic capacitors. They have the lowest ESR (equivalent series resistance) and highest resonance frequency, which makes them optimum for high frequency switching converters. When selecting a ceramic capacitor, only X5R and X7R dielectric types should be used. Other types such as Z5U and Y5F have such severe loss of capacitance due to effects of temperature variation and applied voltage, they may provide as little as 20% of rated capacitance in many typical applications. Always consult capacitor manufacturer's data curves before selecting a capacitor. High-quality ceramic capacitors can be obtained from Taiyo-Yuden, AVX, and Murata. POWER SUPPLY BYPASSING As with any amplifier, proper supply bypassing is critical for low noise performance and high power supply rejection. The capacitor location on both V1 and VDD (Cs2 and Cs1) pins should be as close to the device as possible. SELECTING INPUT CAPACITOR FOR AUDIO AMPLIFIER One of the major considerations is the closedloop bandwidth of the amplifier. To a large extent, the bandwidth is dictated by the choice of external components shown in Figure 2. The input coupling capacitor, Ci, forms a first order high pass filter which limits low frequency response. This value should be chosen based on needed frequency response for a few distinct reasons. High value input capacitors are both expensive and space hungry in portable designs. Clearly, a certain value capacitor is needed to couple in low frequencies without severe attenuation. However, speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 100Hz to 150Hz. Thus, using a high value input capacitor may not increase actual system performance. 14 Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 LM4805 www.ti.com SNAS289B - MAY 2005 - REVISED APRIL 2013 In addition to system cost and size, click and pop performance is affected by the value of the input coupling capacitor, Ci. A high value input coupling capacitor requires more charge to reach its quiescent DC voltage (nominally 1/2 VDD). This charge comes from the output via the feedback and is apt to create pops upon device enable. Thus, by minimizing the capacitor value based on desired low frequency response, turn-on pops can be minimized. SELECTING BYPASS CAPACITOR FOR AUDIO AMPLIFIER Besides minimizing the input capacitor value, careful consideration should be paid to the bypass capacitor value. Bypass capacitor, CB, is the most critical component to minimize turn-on pops since it determines how fast the amplifier turns on. The slower the amplifier's outputs ramp to their quiescent DC voltage (nominally 1/2 VDD), the smaller the turn-on pop. Choosing CB equal to 1.0F along with a small value of Ci (in the range of 0.039F to 0.39F), should produce a virtually clickless and popless shutdown function. Although the device will function properly, (no oscillations or motorboating), with CB equal to 0.1F, the device will be much more susceptible to turn-on clicks and pops. Thus, a value of CB equal to 1.0F is recommended in all but the most cost sensitive designs. SELECTING FEEDBACK CAPACITOR FOR AUDIO AMPLIFIER The LM4805 is unity-gain stable which gives the designer maximum system flexability. However, a typical application requires a closed-loop differential gain of 10. In this case a feedback capacitor (Cf2) can be used as shown in Figure 42 to bandwidth limit the amplifier. This feedback capacitor creates a low pass filter that eliminates possible high frequency oscillations. Care should be taken when calculating the -3dB frequency because an incorrect combination of Rf and Cf2 will cause rolloff before the desired frequency SELECTING OUTPUT CAPACITOR (CO) FOR BOOST CONVERTER A single 4.7F to 10F ceramic capacitor will provide sufficient output capacitance for most applications. If larger amounts of capacitance are desired for improved line support and transient response, tantalum capacitors can be used. Aluminum electrolytics with ultra low ESR such as Sanyo Oscon can be used, but are usually prohibitively expensive. Typical AI electrolytic capacitors are not suitable for switching frequencies above 500 kHz because of significant ringing and temperature rise due to self-heating from ripple current. An output capacitor with excessive ESR can also reduce phase margin and cause instability. In general, if electrolytics are used, we recommended that they be paralleled with ceramic capacitors to reduce ringing, switching losses, and output voltage ripple. SELECTING INPUT CAPACITOR (Cs1) FOR BOOST CONVERTER An input capacitor is required to serve as an energy reservoir for the current which must flow into the coil each time the switch turns ON. This capacitor must have extremely low ESR, so ceramic is the best choice. We recommend a nominal value of 4.7F, but larger values can be used. Since this capacitor reduces the amount of voltage ripple seen at the input pin, it also reduces the amount of EMI passed back along that line to other circuitry. SETTING THE OUTPUT VOLTAGE (V1) OF BOOST CONVERTER The output voltage is set using the external resistors R1 and R2 (see Figure 2). A value of approximately 15k is recommended for R2 to establish a divider current of approximately 92A. R1 is calculated using the formula: R1 = R2 X (V1/1.23 - 1) (6) FEED-FORWARD COMPENSATION FOR BOOST CONVERTER Although the LM4805's internal Boost converter is internally compensated, the external feed-forward capacitor Cf1 is required for stability (see Figure 2). Adding this capacitor puts a zero in the loop response of the converter. The recommended frequency for the zero fz should be approximately 6kHz. Cf1 can be calculated using the formula: Cf1 = 1 / (2 X R1 X fz) (7) Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 15 LM4805 SNAS289B - MAY 2005 - REVISED APRIL 2013 www.ti.com SELECTING DIODES The external diode used in Figure 2 should be a Schottky diode. A 20V diode such as the MBR0520 is recommended. The MBR05XX series of diodes are designed to handle a maximum average current of 0.5A. For applications exceeding 0.5A average but less than 1A, a Microsemi UPS5817 can be used. DUTY CYCLE The maximum duty cycle of the boost converter determines the maximum boost ratio of output-to-input voltage that the converter can attain in continuous mode of operation. The duty cycle for a given boost application is defined as: Duty Cycle = VOUT + VDIODE - VIN/ VOUT + VDIODE - VSW This applies for continuous mode operation. INDUCTANCE VALUE The first question we are usually asked is: "How small can I make the inductor." (because they are the largest sized component and usually the most costly). The answer is not simple and involves trade-offs in performance. Larger inductors mean less inductor ripple current, which typically means less output voltage ripple (for a given size of output capacitor). Larger inductors also mean more load power can be delivered because the energy stored during each switching cycle is: E = L/2 X (lp)2 (8) Where "lp" is the peak inductor current. An important point to observe is that the LM4805 will limit its switch current based on peak current. This means that since lp(max) is fixed, increasing L will increase the maximum amount of power available to the load. Conversely, using too little inductance may limit the amount of load current which can be drawn from the output. Best performance is usually obtained when the converter is operated in "continuous" mode at the load current range of interest, typically giving better load regulation and less output ripple. Continuous operation is defined as not allowing the inductor current to drop to zero during the cycle. It should be noted that all boost converters shift over to discontinuous operation as the output load is reduced far enough, but a larger inductor stays "continuous" over a wider load current range. To better understand these trade-offs, a typical application circuit (5V to 12V boost with a 10H inductor) will be analyzed. We will assume: VIN = 5V, VOUT = 12V, VDIODE = 0.5V, VSW = 0.5V (9) Since the frequency is 1.6MHz (nominal), the period is approximately 0.625s. The duty cycle will be 62.5%, which means the ON-time of the switch is 0.390s. It should be noted that when the switch is ON, the voltage across the inductor is approximately 4.5V. Using the equation: V = L (di/dt) (10) We can then calculate the di/dt rate of the inductor which is found to be 0.45 A/s during the ON-time. Using these facts, we can then show what the inductor current will look like during operation: Figure 42. 10H Inductor Current 5V - 12V Boost (LM4805) 16 Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 LM4805 www.ti.com SNAS289B - MAY 2005 - REVISED APRIL 2013 During the 0.390s ON-time, the inductor current ramps up 0.176A and ramps down an equal amount during the OFF-time. This is defined as the inductor "ripple current". It can also be seen that if the load current drops to about 33mA, the inductor current will begin touching the zero axis which means it will be in discontinuous mode. A similar analysis can be performed on any boost converter, to make sure the ripple current is reasonable and continuous operation will be maintained at the typical load current values. MAXIMUM SWITCH CURRENT The maximum FET switch current available before the current limiter cuts in is dependent on duty cycle of the application. This is illustrated in a graph in the Typical Performance Characteristics section which shows typical values of switch current as a function of effective (actual) duty cycle. CALCULATING OUTPUT CURRENT OF BOOST CONVERTER (IAMP) As shown in Figure 42 which depicts inductor current, the load current is related to the average inductor current by the relation: ILOAD = IIND(AVG) x (1 - DC) (11) Where "DC" is the duty cycle of the application. The switch current can be found by: ISW = IIND(AVG) + 1/2 (IRIPPLE) (12) Inductor ripple current is dependent on inductance, duty cycle, input voltage and frequency: IRIPPLE = DC x (VIN-VSW) / (f x L) (13) combining all terms, we can develop an expression which allows the maximum available load current to be calculated: ILOAD(max) = (1-DC)x(ISW(max)-DC(VIN-VSW))/fL (14) The equation shown to calculate maximum load current takes into account the losses in the inductor or turn-OFF switching losses of the FET and diode. DESIGN PARAMETERS VSW AND ISW The value of the FET "ON" voltage (referred to as VSW in Equation 11 thru Equation 14) is dependent on load current. A good approximation can be obtained by multiplying the "ON Resistance" of the FET times the average inductor current. FET on resistance increases at VIN values below 5V, since the internal N-FET has less gate voltage in this input voltage range (see Typical Performance Characteristics curves). Above VIN = 5V, the FET gate voltage is internally clamped to 5V. The maximum peak switch current the device can deliver is dependent on duty cycle. For higher duty cycles, see Typical Performance Characteristics curves. INDUCTOR SUPPLIERS Recommended suppliers of inductors for the LM4805 include, but are not limited to Taiyo-Yuden, Sumida, Coilcraft, Panasonic, TDK and Murata. When selecting an inductor, make certain that the continuous current rating is high enough to avoid saturation at peak currents. A suitable core type must be used to minimize core (switching) losses, and wire power losses must be considered when selecting the current rating. PCB LAYOUT GUIDELINES High frequency boost converters require very careful layout of components in order to get stable operation and low noise. All components must be as close as possible to the LM4805 device. It is recommended that a 4-layer PCB be used so that internal ground planes are available. Some additional guidelines to be observed: 1. Keep the path between L1, D1, and Co extremely short. Parasitic trace inductance in series with D1 and Co will increase noise and ringing. 2. The feedback components R1, R2 and Cf 1 must be kept close to the FB pin of U1 to prevent noise injection on the FB pin trace. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 17 LM4805 SNAS289B - MAY 2005 - REVISED APRIL 2013 www.ti.com 3. If internal ground planes are available (recommended) use vias to connect directly to ground at pin 2 of U1, as well as the negative sides of capacitors Cs1 and Co. GENERAL MIXED-SIGNAL LAYOUT RECOMMENDATION This section provides practical guidelines for mixed signal PCB layout that involves various digital/analog power and ground traces. Designers should note that these are only "rule-of-thumb" recommendations and the actual results will depend heavily on the final layout. Power and Ground Circuits For 2 layer mixed signal design, it is important to isolate the digital power and ground trace paths from the analog power and ground trace paths. Star trace routing techniques (bringing individual traces back to a central point rather than daisy chaining traces together in a serial manner) can have a major impact on low level signal performance. Star trace routing refers to using individual traces to feed power and ground to each circuit or even device. This technique will take require a greater amount of design time but will not increase the final price of the board. The only extra parts required may be some jumpers. Single-Point Power / Ground Connection The analog power traces should be connected to the digital traces through a single point (link). A "Pi-filter" can be helpful in minimizing high frequency noise coupling between the analog and digital sections. It is further recommended to place digital and analog power traces over the corresponding digital and analog ground traces to minimize noise coupling. Placement of Digital and Analog Components All digital components and high-speed digital signals traces should be located as far away as possible from analog components and circuit traces. Avoiding Typical Design / Layout Problems Avoid ground loops or running digital and analog traces parallel to each other (side-by-side) on the same PCB layer. When traces must cross over each other do it at 90 degrees. Running digital and analog traces at 90 degrees to each other from the top to the bottom side as much as possible will minimize capacitive noise coupling and crosstalk. 18 Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 LM4805 www.ti.com SNAS289B - MAY 2005 - REVISED APRIL 2013 VDD D2 L1 10 PH Cs1 4.7 PF 4 7 12 6 18 19 Cb 1.0 PF 21 C3 470 pF 11 C2 4.7 PF R2 51.1k SW VDD VDD V1 = VFB (1 + R1/R2) GND1 FB 8 R3 15k GND2 S/D1 V1 S/D2 Bypass GND3 +IN VO2 26 20 Cs2 4.7 PF 17 RL 8: 20k 22 Audio In -IN VO1 25 0.1 PF RINA CINA RfA 200k Figure 43. Demo Board Reference Schematic Demonstration Board Layout Figure 44. Composite Layer Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 19 LM4805 SNAS289B - MAY 2005 - REVISED APRIL 2013 www.ti.com Figure 45. Top Layer Figure 46. Silkscreen Figure 47. Bottom Layer 20 Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 LM4805 www.ti.com SNAS289B - MAY 2005 - REVISED APRIL 2013 Revision History Rev Date Description 1.0 8/11/05 Changed the project title from 3V, 1W Boosted Amplifier into Low Voltage High Power Audio Power Amplifier (per Nisha P.), then re-released D/S to the WEB. B 4/08/13 Changed layout of National Data Sheet to TI format. Submit Documentation Feedback Copyright (c) 2005-2013, Texas Instruments Incorporated Product Folder Links: LM4805 21 PACKAGE OPTION ADDENDUM www.ti.com 11-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) LM4805LQ/NOPB ACTIVE WQFN NJB 28 1000 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 85 L4805LQ LM4805LQX/NOPB ACTIVE WQFN NJB 28 4500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 85 L4805LQ (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. 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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 LM4805LQ/NOPB WQFN NJB 28 1000 178.0 12.4 5.3 5.3 1.3 8.0 12.0 Q1 LM4805LQX/NOPB WQFN NJB 28 4500 330.0 12.4 5.3 5.3 1.3 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) LM4805LQ/NOPB WQFN NJB 28 1000 213.0 191.0 55.0 LM4805LQX/NOPB WQFN NJB 28 4500 367.0 367.0 35.0 Pack Materials-Page 2 MECHANICAL DATA NJB0028A LQA28A (REV B) 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. 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