LM4995, LM4995TMBD www.ti.com SNAS329G - APRIL 2006 - REVISED APRIL 2013 LM4995 1.3 W Audio Power Amplifier Check for Samples: LM4995, LM4995TMBD FEATURES DESCRIPTION * The LM4995 is an audio power amplifier primarily designed for demanding applications in mobile phones and other portable communication device applications. It is capable of delivering 1.2W of continuous average power to an 8 BTL load with less than 1% distortion (THD+N) from a 5VDC power supply. 1 2 * * * * * * * * Available in Space-Saving 0.4mm Pitch DSBGA Package Ultra Low Current Shutdown Mode BTL Output Can Drive Capacitive Loads Improved Click and Pop Circuitry Eliminates Noise during Turn-On and Turn-Off Transitions 2.4 - 5.5V Operation No Output Coupling Capacitors, Snubber Networks or Bootstrap Capacitors Required Unity-Gain Stable External Gain Configuration Capability WSON Package: 0.5mm Pitch, 3 x 3 mm APPLICATIONS * * * Mobile Phones PDAs Portable electronic devices KEY SPECIFICATIONS * * * * PSRR at 3.6V (217Hz & 1kHz): 75 dB Output Power at 5.0V, 1% THD+N, 8: 1.3 W (typ) Output Power at 3.6V, 1% THD+N, 8: 625 mW (typ) Shutdown Current: 0.01A (typ) Boomer audio power amplifiers were designed specifically to provide high quality output power with a minimal amount of external components. The LM4995 does not require output coupling capacitors or bootstrap capacitors, and therefore is ideally suited for mobile phone and other low voltage applications where minimal power consumption is a primary requirement. The LM4995 features a low-power consumption shutdown mode, which is achieved by driving the shutdown pin with logic low. Additionally, the LM4995 features an internal thermal shutdown protection mechanism. The LM4995 contains advanced click and pop circuitry which eliminates noise which would otherwise occur during turn-on and turn-off transitions. The LM4995 is unity-gain stable and can be configured by external gain-setting resistors. 1 2 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. All 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) 2006-2013, Texas Instruments Incorporated LM4995, LM4995TMBD SNAS329G - APRIL 2006 - REVISED APRIL 2013 www.ti.com TYPICAL APPLICATION Figure 1. Typical Audio Amplifier Application Circuit CONNECTION DIAGRAM xxx xxx 3 2 1 -IN GND BYP A VO1 GND +IN SHUTDOWN 1 8 VO2 BYPASS 2 7 GND +IN 3 6 VDD -IN 4 5 VO1 VDD VO2 SHDN B C Figure 3. WSON (Top View) See NGQ0008A Package Figure 2. DSBGA (Top View) See YFQ0009 Package 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) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD LM4995, LM4995TMBD www.ti.com SNAS329G - APRIL 2006 - REVISED APRIL 2013 ABSOLUTE MAXIMUM RATINGS (1) (2) Supply Voltage (3) 6.0V -65C to +150C Storage Temperature -0.3V to VDD +0.3V Input Voltage Power Dissipation (4) (5) ESD Susceptibility Internally Limited (6) 2000V ESD Susceptibility (7) 200V Junction Temperature 150C Thermal Resistance JA (DSBGA) JA (WSON) (1) (2) (3) (4) (5) (6) (7) 96.5C/W 56C/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 ensure 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. If the product is in Shutdown mode and VDD exceeds 6V (to a max of 8V VDD), then most of the excess current will flow through the ESD protection circuits. If the source impedance limits the current to a max of 10mA, then the device will be protected. If the device is enabled when VDD is greater than 5.5V and less than 6.5V, no damage will occur, although operation life will be reduced. Operation above 6.5V with no current limit will result in permanent damage. 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 number given in Absolute Maximum Ratings, whichever is lower. For the LM4995, see power derating curves for additional information. Maximum power dissipation in the device (PDMAX) occurs at an output power level significantly below full output power. PDMAX can be calculated using Equation 1 shown in the APPLICATION INFORMATION section. It may also be obtained from the power dissipation graphs. 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 2.4V VDD 5.5V Supply Voltage Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD Submit Documentation Feedback 3 LM4995, LM4995TMBD SNAS329G - APRIL 2006 - REVISED APRIL 2013 www.ti.com ELECTRICAL CHARACTERISTICS VDD = 5V (1) (2) The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for TA = 25C. Symbol Parameter Conditions LM4995 Typical (3) Limit (4) (5) Units (Limits) 2.5 mA (max) VIN = 0V, Io = 0A, No Load 1.5 VIN = 0V, Io = 0A, 8 Load 1.8 Shutdown Current VSD = VGND 0.01 1 A (max) VOS Output Offset Voltage No Load 5 26 mV (max) Po Output Power THD+N = 1% (max); f = 1 kHz TWU Wake-up time THD+N Total Harmonic Distortion + Noise Po = 500mWRMS; f = 1kHz PSRR Power Supply Rejection Ratio Vripple = 200mV sine p-p Input terminated to GND VSDIH Shutdown Voltage Input High 1.5 V VSDIL Shutdown Voltage Input Low 1.2 V IDD Quiescent Power Supply Current ISD (1) (2) (3) (4) (5) mA 1.3 (TM) 1.25 (SD) W 165 ms 0.08 % 73 (f = 217Hz) 73 (f = 1kHz) dB All voltages are measured with respect to the ground 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 ensure 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 AOQL (Average Outgoing Quality Level). Datasheet min/max specification limits are specified by design, test, or statistical analysis. ELECTRICAL CHARACTERISTICS VDD = 3.6V (1) (2) The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for TA = 25C. Symbol Parameter LM4995 Conditions VIN = 0V, Io = 0A, No Load Typical (3) Limit (4) (5) Units (Limits) 1.3 2.3 mA (max) IDD Quiescent Power Supply Current VIN = 0V, Io = 0A, 8 Load 1.6 ISD Shutdown Current VSD = VGND 0.01 1 A (max) VOS Output Offset Voltage No Load 5 26 mV (max) Output Power THD+N = 1% (max); f = 1 kHz Po mA 625 (TM) 610 (SD) mW 130 ms 0.07 % TWU Wake-up time THD+N Total Harmonic Distortion + Noise Po = 300mWRMS; f = 1kHz PSRR Power Supply Rejection Ratio Vripple = 200mV sine p-p Input terminated to GND VSDIH Shutdown Voltage Input High 1.3 V VSDIL Shutdown Voltage Input Low 1 V (1) (2) (3) (4) (5) 4 75 (f = 217Hz) 76 (f = 1kHz) dB All voltages are measured with respect to the ground 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 ensure 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 AOQL (Average Outgoing Quality Level). Datasheet min/max specification limits are specified by design, test, or statistical analysis. Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD LM4995, LM4995TMBD www.ti.com SNAS329G - APRIL 2006 - REVISED APRIL 2013 ELECTRICAL CHARACTERISTICS VDD = 3.0V (1) (2) The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for TA = 25C. Symbol Parameter LM4995 Conditions Typical (3) Limit (4) (5) Units (Limits) VIN = 0V, Io = 0A, No Load 1.3 mA VIN = 0V, Io = 0A, 8 Load 1.6 mA Shutdown Current VSD = VGND 0.01 A VOS Output Offset Voltage No Load Po Output Power THD+N = 1% (max); f = 1 kHz TWU Wake-up time THD+N Total Harmonic Distortion + Noise Po = 250mWRMS; f = 1kHz PSRR Power Supply Rejection Ratio Vripple = 200mV sine p-p Input terminated to GND VSDIH Shutdown Voltage Input High 1.2 V VSDIL Shutdown Voltage Input Low 1 V IDD Quiescent Power Supply Current ISD (1) (2) (3) (4) (5) 5 mV 400 mW 110 ms 0.07 % 74 (f = 217Hz) 75 (f = 1kHz) dB All voltages are measured with respect to the ground 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 ensure 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 AOQL (Average Outgoing Quality Level). Datasheet min/max specification limits are specified by design, test, or statistical analysis. EXTERNAL COMPONENTS DESCRIPTION (Figure 1) Components Functional Description 1. Ri Inverting input resistance which sets the closed-loop gain in conjunction with Rf. This resistor also forms a high pass filter with Ci at fC= 1/(2 RiCi). 2. Ci Input coupling capacitor which blocks the DC voltage at the amplifiers input terminals. Also creates a highpass filter with Ri at fC = 1/(2 RiCi). Refer to the section, PROPER SELECTION OF EXTERNAL COMPONENTS, for an explanation of how to determine the value of Ci. 3. Rf Feedback resistance which sets the closed-loop gain in conjunction with Ri. 4. CS Supply bypass capacitor which provides power supply filtering. Refer to the POWER SUPPLY BYPASSING section for information concerning proper placement and selection of the supply bypass capacitor. 5. CB Bypass pin capacitor which provides half-supply filtering. Refer to the section, PROPER SELECTION OF EXTERNAL COMPONENTS, for information concerning proper placement and selection of CB. Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD Submit Documentation Feedback 5 LM4995, LM4995TMBD SNAS329G - APRIL 2006 - REVISED APRIL 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS THD+N vs Output Power VDD = 3V, RL = 8 THD+N vs Output Power VDD = 3.6V, RL = 8 10 10 5 5 2 2 1 THD+N (%) THD+N (%) 1 0.5 0.2 0.1 0.05 0.05 0.02 0.02 20 50 100 200 500 100 200 500 Figure 4. Figure 5. THD+N vs Output Power VDD = 5V, RL = 8 THD+N vs Frequency VDD = 3V, RL = 8, f = 1kHz, PO = 250mW 10 5 5 2 2 1000 1 0.5 0.2 0.5 0.2 0.1 0.1 0.05 0.05 0.02 0.02 50 100 200 500 0.01 20 1000 2000 50 100 200 500 1k 2k 5k 10k 20k OUTPUT POWER (mW) FREQUENCY (Hz) Figure 6. Figure 7. THD+N vs Frequency VDD = 3.6V, RL = 8, f = 1kHz, PO = 300mW THD+N vs Frequency VDD = 5V, RL = 8, f = 1kHz, PO = 500mW 10 10 5 5 2 2 1 THD+N (%) 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 OUTPUT POWER (mW) 10 0.01 20 20 OUTPUT POWER (mW) THD+N (%) THD+N (%) 0.01 10 1000 1 THD+N (%) 0.2 0.1 0.01 10 6 0.5 50 100 200 500 1k 2k 5k 10k 20k 0.01 20 50 100 200 500 1k 2k FREQUENCY (Hz) FREQUENCY (Hz) Figure 8. Figure 9. Submit Documentation Feedback 5k 10k 20k Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD LM4995, LM4995TMBD www.ti.com SNAS329G - APRIL 2006 - REVISED APRIL 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) PSRR vs Frequency VDD = 3V, RL = 8 -10 -10 -20 -20 -30 -30 -40 -50 -60 -40 -50 -60 -70 -70 -80 -80 -90 -90 -100 20 50 100 200 500 1k 2k PSRR vs Frequency VDD = 3.6V, RL = 8 0 PSRR (dB) PSRR (dB) 0 -100 20 5k 10k 20k 50 100 200 5k 10k 20k FREQUENCY (Hz) FREQUENCY (Hz) 0 500 1k 2k Figure 10. Figure 11. PSRR vs Frequency VDD = 5V, RL = 8 Power Dissipation vs Output Power VDD = 3V, RL = 8 250 POWER DISSIPATION (mW) -10 -20 PSRR (dB) -30 -40 -50 -60 -70 -80 200 150 100 50 -90 -100 0 50 100 200 500 1k 2k 0 5k 10k 50 150 200 250 300 350 OUTPUT POWER (mW) FREQUENCY (Hz) Figure 12. Figure 13. Power Dissipation vs Output Power VDD = 3.6V, RL = 8 Power Dissipation vs Output Power VDD = 5V, RL = 8 350 700 300 600 POWER DISSIPATION (mW) POWER DISSIPATION (mW) 100 250 200 150 100 500 400 300 200 100 50 0 0 0 100 200 300 400 500 600 0 OUTPUT POWER (mW) Figure 14. 200 400 600 800 1000 1200 OUTPUT POWER (mW) Figure 15. Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD Submit Documentation Feedback 7 LM4995, LM4995TMBD SNAS329G - APRIL 2006 - REVISED APRIL 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) Output Level vs Frequency Response (Three different caps) +1 Ci = 1PF (tantulum) 0 Ci = 1PF (ceramic) 90 SUPPLY CURRENT (mA) OUTPUT LEVEL (dB) -1 -2 -3 Shutdown Voltage VSDIH VDD = 3V 100 Ci = 0.33PF (tantulum) -4 -5 -6 -7 -8 80 70 60 50 40 30 20 10 -9 -10 20 0 50 100 200 500 1k 2k 0 5k 10k 20k 0.2 FREQUENCY (Hz) 1.0 1.2 Figure 17. Shutdown Voltage VSDIH VDD = 3.6V Shutdown Voltage VSDIH VDD = 5V 100 90 90 80 80 SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 0.8 1.4 1.6 1.4 1.6 SHUTDOWN VOLTAGE (V) 70 60 50 40 30 20 70 60 50 40 30 20 10 10 0 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0 1.6 0.2 100 0.4 0.6 0.8 1.0 1.2 SHUTDOWN VOLTAGE (V) SHUTDOWN VOLTAGE (V) Figure 18. Figure 19. Shutdown Voltage VSDIL VDD = 3V Shutdown Voltage VSDIL VDD = 3.6V 100 90 90 80 SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 0.6 Figure 16. 100 70 60 50 40 30 20 10 80 70 60 50 40 30 20 10 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0 0 0.2 SHUTDOWN VOLTAGE (V) Submit Documentation Feedback 0.4 0.6 0.8 1.0 1.2 1.4 1.6 SHUTDOWN VOLTAGE (V) Figure 20. 8 0.4 Figure 21. Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD LM4995, LM4995TMBD www.ti.com SNAS329G - APRIL 2006 - REVISED APRIL 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) Shutdown Voltage VSDIL VDD = 5V 2000 90 1800 80 1600 OUTPUT POWER (mW) SUPPLY CURRENT (mA) 100 70 60 50 40 30 20 Output Power vs Supply Voltage RL = 8 1400 THD+N = 10% 1200 1000 800 THD+N = 1% 600 400 10 200 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0 2.0 SHUTDOWN VOLTAGE (V) Figure 22. 3.0 4.0 5.0 6.0 VOLTAGE SUPPLY (V) Figure 23. Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD Submit Documentation Feedback 9 LM4995, LM4995TMBD SNAS329G - APRIL 2006 - REVISED APRIL 2013 www.ti.com APPLICATION INFORMATION BRIDGE CONFIGURATION EXPLANATION As shown in Figure 1, the LM4995 has two internal operational amplifiers. The first amplifier's gain is externally configurable, while 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 1 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 Vo1 and Vo2, 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 closedloop gain without causing excessive clipping, please refer to the AUDIO POWER AMPLIFIER DESIGN section. A bridge configuration, such as the one used in LM4995, 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, singleended 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. 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 LM4995 has two operational amplifiers in one package, the maximum internal power dissipation 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 (1). PDMAX = 4*(VDD)2/(22RL) (2) It is critical that the maximum junction temperature TJMAX of 150C is not exceeded. TJMAX can be determined from the power derating curves by using PDMAX and the PC board foil area. By adding copper foil, the thermal resistance of the application can be reduced from the free air value of JA, resulting in higher PDMAX values without thermal shutdown protection circuitry being activated. Additional copper foil can be added to any of the leads connected to the LM4995. It is especially effective when connected to VDD, GND, and the output pins. Refer to the application information on the LM4995 reference design board for an example of good heat sinking. If TJMAX still exceeds 150C, then additional changes must be made. These changes can include reduced supply voltage, higher load impedance, or reduced ambient temperature. Internal power dissipation is a function of output power. Refer to the TYPICAL PERFORMANCE CHARACTERISTICS curves for power dissipation information for different output powers and output loading. POWER SUPPLY BYPASSING As with any amplifier, proper supply bypassing is critical for low noise performance and high supply rejection. The capacitor location on both the bypass and power supply pins should be as close to the device as possible. A ceramic 0.1F placed in parallel with the tantalum 2.2F bypass (CB) capacitor will aid in supply stability. This does not eliminate the need for bypassing the power supply pins of the LM4995. The selection of a bypass capacitor, especially CB, is dependent upon PSRR requirements, click and pop performance (as explained in the section, PROPER SELECTION OF EXTERNAL COMPONENTS), system cost, and size constraints. 10 Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD LM4995, LM4995TMBD www.ti.com SNAS329G - APRIL 2006 - REVISED APRIL 2013 SHUTDOWN FUNCTION In order to reduce power consumption while not in use, the LM4995 contains shutdown circuitry that is used to turn off the amplifier's bias circuitry. This shutdown feature turns the amplifier off when logic low is placed on the shutdown pin. By switching the shutdown pin to GND, the LM4995 supply current draw will be minimized in idle mode. Idle current is measured with the shutdown pin connected to GND. The trigger point for shutdown is shown as a typical value in the Shutdown Hysteresis Voltage graphs in the TYPICAL PERFORMANCE CHARACTERISTICS section. It is best to switch between ground and supply for maximum performance. While the device may be disabled with shutdown voltages in between ground and supply, the idle current may be greater than the typical value of 0.01A. In either case, the shutdown pin should be tied to a definite voltage to avoid unwanted state changes. In many applications, a microcontroller or microprocessor output is used to control the shutdown circuitry, which provides a quick, smooth transition to shutdown. Another solution is to use a single-throw switch in conjunction with an external pull-up resistor. This scheme ensures that the shutdown pin will not float, thus preventing unwanted state changes. 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 LM4995 is tolerant of external component combinations, consideration to component values must be used to maximize overall system quality. The LM4995 is unity-gain stable which gives the designer maximum system flexibility. The LM4995 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 1 Vrms are available from sources such as audio codecs. 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 1. 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. SELECTION OF INPUT CAPACITOR SIZE Large input capacitors are both expensive and space hungry for portable designs. Clearly, a certain sized capacitor is needed to couple in low frequencies without severe attenuation. But in many cases the speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 100Hz to 150Hz. Thus, using a large input capacitor may not increase actual system performance. In addition to system cost and size, click and pop performance is effected by the size of the input coupling capacitor, Ci. A larger 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 size based on necessary low frequency response, turn-on pops can be minimized. Besides minimizing the input capacitor size, 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 LM4995 turns on. The slower the LM4995'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 0.1F to 0.39F), should produce a virtually clickless and popless shutdown function. While 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. Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD Submit Documentation Feedback 11 LM4995, LM4995TMBD SNAS329G - APRIL 2006 - REVISED APRIL 2013 www.ti.com AUDIO POWER AMPLIFIER DESIGN A 1W/8 AUDIO AMPLIFIER Given: Power Output 1 Wrms Load Impedance 8 Input Level 1 Vrms Input Impedance 20 k Bandwidth 100 Hz-20 kHz 0.25 dB A designer must first 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. 5V is a standard voltage in most applications, it is chosen for the supply rail. Extra supply voltage creates headroom that allows the LM4995 to reproduce peaks in excess of 1W 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 differential gain can be determined from Equation (3). (3) Rf/Ri = AVD/2 (4) From Equation (3), the minimum AVD is 2.83; use AVD = 3. Since the desired input impedance was 20 k, and with a AVD impedance of 2, a ratio of 1.5:1 of Rf to Ri results in an allocation of Ri = 20 k and Rf = 30 k. The final design step is to address the bandwidth requirements which must be stated as a pair of -3 dB frequency points. Five times away from a -3 dB point is 0.17 dB down from passband response which is better than the required 0.25 dB specified. fL = 100Hz/5 = 20Hz fH = 20kHz * 5 = 100kHz As stated in the EXTERNAL COMPONENTS DESCRIPTION section, Ri in conjunction with Ci create a highpass filter. Ci 1/(2*20 k*20 Hz) = 0.397 F; use 0.39 F The high frequency pole is determined by the product of the desired frequency pole, fH, and the differential gain, AVD. With a AVD = 3 and fH = 100kHz, the resulting GBWP = 300kHz which is much smaller than the LM4995 GBWP of 2.5MHz. This figure displays that if a designer has a need to design an amplifier with a higher differential gain, the LM4995 can still be used without running into bandwidth limitations. The LM4995 is unity-gain stable and requires no external components besides gain-setting resistors, an input coupling capacitor, and proper supply bypassing in the typical application. However, if a closed-loop differential gain of greater than 10 is required, a feedback capacitor (C4) may be needed as shown in Figure 24 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 in that an incorrect combination of R3 and C4 will cause rolloff before 20kHz. A typical combination of feedback resistor and capacitor that will not produce audio band high frequency rolloff is R3 = 20k and C4 = 25pf. These components result in a -3dB point of approximately 320kHz. 12 Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD LM4995, LM4995TMBD www.ti.com SNAS329G - APRIL 2006 - REVISED APRIL 2013 Figure 24. HIGHER GAIN AUDIO AMPLIFIER Figure 25. DIFFERENTIAL AMPLIFIER CONFIGURATION FOR LM4995 Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD Submit Documentation Feedback 13 LM4995, LM4995TMBD SNAS329G - APRIL 2006 - REVISED APRIL 2013 www.ti.com Figure 26. REFERENCE DESIGN BOARD SCHEMATIC PCB LAYOUT GUIDELINES 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. GENERAL MIXED SIGNAL LAYOUT RECOMMENDATION 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 require a greater amount of design time but will not increase the final price of the board. The only extra parts required will be some jumpers. SINGLE-POINT POWER / GROUND CONNECTIONS 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 put 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 signal 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 cross talk. 14 Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD LM4995, LM4995TMBD www.ti.com SNAS329G - APRIL 2006 - REVISED APRIL 2013 REVISION HISTORY Rev Date Description 1.0 04/05/06 Initial WEB released of the datasheet. 1.1 05/17/06 Added the SD package. 1.2 08/07/06 Text edits. 1.3 08/22/06 Edited the THD+N Typical values on the 3 EC tables, then re-released the D/S to the WEB (per Allan S.). 1.4 09/11/07 Updated the SD pkg. diagram. Changes from Revision F (April 2013) to Revision G * Page Changed layout of National Data Sheet to TI format .......................................................................................................... 14 Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM4995 LM4995TMBD Submit Documentation Feedback 15 PACKAGE OPTION ADDENDUM www.ti.com 20-Jan-2017 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (C) Device Marking (4/5) LM4995SD/NOPB ACTIVE WSON NGQ 8 1000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM L4995 LM4995TM/NOPB ACTIVE DSBGA YFQ 9 250 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM -40 to 85 G G8 LM4995TMX/NOPB ACTIVE DSBGA YFQ 9 3000 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM -40 to 85 G G8 (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) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device 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 Device Marking for that device. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. 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 Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 20-Jan-2017 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 2 PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing LM4995SD/NOPB WSON NGQ 8 LM4995TM/NOPB DSBGA YFQ LM4995TMX/NOPB DSBGA YFQ SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 1000 178.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1 9 250 178.0 8.4 1.35 1.35 0.76 4.0 8.0 Q1 9 3000 178.0 8.4 1.35 1.35 0.76 4.0 8.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM4995SD/NOPB WSON NGQ 8 1000 210.0 185.0 35.0 LM4995TM/NOPB DSBGA YFQ 9 250 210.0 185.0 35.0 LM4995TMX/NOPB DSBGA YFQ 9 3000 210.0 185.0 35.0 Pack Materials-Page 2 MECHANICAL DATA YFQ0009xxx D 0.6000.075 E TMD09XXX (Rev A) D: Max = 1.24 mm, Min = 1.18 mm E: Max = 1.24 mm, Min = 1.18 mm 4215077/A NOTES: A. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994. B. This drawing is subject to change without notice. www.ti.com 12/12 PACKAGE OUTLINE NGQ0008A WSON - 0.8 mm max height SCALE 4.000 PLASTIC SMALL OUTLINE - NO LEAD 3.1 2.9 B A PIN 1 INDEX AREA 3.1 2.9 C 0.8 0.7 SEATING PLANE 0.08 C 1.6 0.1 (0.1) TYP SYMM EXPOSED THERMAL PAD 0.05 0.00 4 5 SYMM 9 2X 1.5 2 0.1 8 1 6X 0.5 8X PIN 1 ID 8X 0.5 0.3 0.3 0.2 0.1 0.05 C A B C 4214922/A 03/2018 NOTES: 1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing per ASME Y14.5M. 2. This drawing is subject to change without notice. 3. The package thermal pad must be soldered to the printed circuit board for thermal and mechanical performance. www.ti.com EXAMPLE BOARD LAYOUT NGQ0008A WSON - 0.8 mm max height PLASTIC SMALL OUTLINE - NO LEAD (1.6) SYMM 8X (0.6) 1 8 (0.75) 8X (0.25) 9 SYMM (2) 6X (0.5) 5 4 (R0.05) TYP ( 0.2) VIA TYP (2.8) LAND PATTERN EXAMPLE EXPOSED METAL SHOWN SCALE:20X 0.07 MIN ALL AROUND 0.07 MAX ALL AROUND EXPOSED METAL EXPOSED METAL SOLDER MASK OPENING METAL METAL UNDER SOLDER MASK NON SOLDER MASK DEFINED (PREFERRED) SOLDER MASK OPENING SOLDER MASK DEFINED SOLDER MASK DETAILS 4214922/A 03/2018 NOTES: (continued) 4. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature number SLUA271 (www.ti.com/lit/slua271). 5. Vias are optional depending on application, refer to device data sheet. If any vias are implemented, refer to their locations shown on this view. It is recommended that vias under paste be filled, plugged or tented. www.ti.com EXAMPLE STENCIL DESIGN NGQ0008A WSON - 0.8 mm max height PLASTIC SMALL OUTLINE - NO LEAD 8X (0.6) SYMM 9 METAL TYP 8 1 8X (0.25) SYMM (1.79) 6X (0.5) 5 4 (R0.05) TYP (1.47) (2.8) SOLDER PASTE EXAMPLE BASED ON 0.1 mm THICK STENCIL EXPOSED PAD 9: 82% PRINTED SOLDER COVERAGE BY AREA UNDER PACKAGE SCALE:20X 4214922/A 03/2018 NOTES: (continued) 6. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate design recommendations. www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated (TI) reserves 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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