LM4940TSBD/NOPB

LM4940 www.ti.com SNAS219C – OCTOBER 2003 – REVISED MAY 2013 LM4940 6W Stereo Audio Power Amplifier Check for Samples: LM4940 FEATURES DESCRIPTION • The LM4940 is a dual audio power amplifier primarily designed for demanding applications in flat panel monitors and TVs. It is capable of delivering 6 watts per channel to a 4Ω load with less than 10% THD+N while operating on a 14.4VDC power supply. 1 23 • • • • • • Click and Pop Circuitry Eliminates Noise During Turn-On and Turn-Off Transitions Low Current, Active-Low Shutdown Mode Low Quiescent Current Stereo 6W Output, RL = 4Ω Short Circuit Protection Unity-Gain Stable External Gain Configuration Capability APPLICATIONS • • • Boomer™ audio power amplifiers were designed specifically to provide high quality output power with a minimal amount of external components. The LM4940 does not require bootstrap capacitors or snubber circuits. Therefore, it is ideally suited for display applications requiring high power and minimal size. Flat Panel Monitors Flat Panel TVs Computer Sound Cards The LM4940 features a low-power consumption active-low shutdown mode. Additionally, the LM4940 features an internal thermal shutdown protection mechanism along with short circuit protection. KEY SPECIFICATIONS The LM4940 contains advanced pop and click circuitry that eliminates noises which would otherwise occur during turn-on and turn-off transitions. • • • Quiscent Power Supply Current: 40mA (max) (SE) POUT VDD = 14.4V, RL = 4Ω, 10% THD+N: 6 W (typ) Shutdown Current: 40µA (typ) The LM4940 is a unity-gain stable and can be configured by external gain-setting resistors. TYPICAL APPLICATION Figure 1. Typical Stereo Audio Amplifier Application Circuit 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, Inc. 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 © 2003–2013, Texas Instruments Incorporated LM4940 SNAS219C – OCTOBER 2003 – REVISED MAY 2013 www.ti.com CONNECTION DIAGRAM U = Wafer Fab Code, Z = Assembly Plant Code, XY = Date Code, TT = Die Traceability Plastic Package, DDPAK Top View See Package Number KTW 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 © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 LM4940 www.ti.com SNAS219C – OCTOBER 2003 – REVISED MAY 2013 ABSOLUTE MAXIMUM RATINGS (1) (2) (3) Supply Voltage (pin 6, referenced to GND, pins 4 and 5) 18.0V −65°C to +150°C Storage Temperature Input Voltage Pins 3 and 7 Pins 1, 2, 8, and 9 −0.3V to VDD + 0.3V −0.3V to 9.5V (4) Internally limited ESD Susceptibility (5) 2000V ESD Susceptibility (6) 200V Power Dissipation Junction Temperature Thermal Resistance 150°C θJC (KTW) θJA (KTW) (4) 4°C/W 20°C/W θJC (NEC) θJA (NEC) (4) (1) (2) (3) (4) (5) (6) 4°C/W 20°C/W 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 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, θJA, and the ambient temperature, TA. The maximum allowable power dissipation is P DMAX = (TJMAX − TA) / θJA or the given in Absolute Maximum Ratings, whichever is lower. For the LM4940 typical application (shown in Figure 1) with VDD = 12V, RL = 4Ω stereo operation the total power dissipation is 3.65W. θJA = 20°C/W for both DDPAK and TO–220 packages mounted to 16in2 heatsink surface area. Human body model, 100pF discharged through a 1.5kΩ resistor. Machine Model, 220pF–240pF discharged through all pins. OPERATING RATINGS Temperature Range (TMIN ≤ TA ≤ TMAX) −40°C ≤ T A ≤ 85°C 10V ≤ VDD ≤ 16V Supply Voltage Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 3 LM4940 SNAS219C – OCTOBER 2003 – REVISED MAY 2013 www.ti.com ELECTRICAL CHARACTERISTICS VDD = 12V (1) (2) The following specifications apply for VDD = 12V, AV = 10, RL = 4Ω, f = 1kHz unless otherwise specified. Limits apply for TA = 25°C. Symbol Parameter LM4940 Conditions Typical (3) Limit (4) (5) Units (Limits) IDD Quiescent Power Supply Current VIN = 0V, IO = 0A, No Load 16 40 mA (max) ISD Shutdown Current VSHUTDOWN = GND (6) 40 100 µA (max) 2.0 VDD/2 V (min) V (max) 0.4 V (max) VSDIH Shutdown Voltage Input High VSDIL Shutdown Voltage Input Low Single Channel THD+N = 1% 3.1 THD+N = 10% 4.2 2.8 PO Output Power VDD = 14.4V, THD+N = 10% 6.0 THD+N Total Harmomic Distortion + Noise PO = 1WRMS, AV = 10, f = 1kHz 0.15 % εOS Output Noise A-Weighted Filter, VIN = 0V, Input Referred 10 µV XTALK Channel Separation PO = 1W 70 dB Power Supply Rejection Ratio VRIPPLE = 200mVp-p fRIPPLE = 1kHz 56 dB PSRR (1) (2) (3) (4) (5) (6) W (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 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 25°C 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. Shutdown current is measured in a normal room environment. The Shutdown pin should be driven as close as possible to GND for minimum shutdown current. TYPICAL APPLICATION Figure 2. Typical Stereo Audio Amplifier Application Circuit 4 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 LM4940 www.ti.com SNAS219C – OCTOBER 2003 – REVISED MAY 2013 EXTERNAL COMPONENTS DESCRIPTION Refer to Figure 1. Components Functional Description 1. RIN This is the inverting input resistance that, along with RF, sets the closed-loop gain. Input resistance RIN and input capacitance CIN form a high pass filter. The filter's cutoff frequency is fC = 1/(2πRINCIN). 2. CIN This is the input coupling capacitor. It blocks DC voltage at the amplifier's inverting input. CIN and RIN create a highpass filter. The filter's cutoff frequency is fC = 1/(2πRINCIN). Refer to the SELECTING EXTERNAL COMPONENTS section for an explanation of determining CIN's value. 3. RF This is the feedback resistance that, along with Ri, sets closed-loop gain. 4. CS The supply bypass capacitor. Refer to the POWER SUPPLY BYPASSING section for information about properly placing, and selecting the value of, this capacitor. 5. CBYPASS This capacitor filters the half-supply voltage present on the BYPASS pin. Refer to the SELECTING EXTERNAL COMPONENTS for information about properly placing, and selecting the value of, this capacitor. 6. COUT This is the output coupling capacitor. It blocks the nominal VDD/2 voltage present at the output and prevents it from reaching the load. COUT and RL form a high pass filter whose cutoff frequency is fC = 1/(2πRLCOUT). Refer to the SELECTING EXTERNAL COMPONENTS section for an explanation of determining COUT's value. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 5 LM4940 SNAS219C – OCTOBER 2003 – REVISED MAY 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS THD+N vs Frequency THD+N vs Frequency VDD = 12V, RL = 4Ω, SE operation, both channels driven and loaded (average shown) POUT = 1W, AV = 1 Figure 3. VDD = 12V, RL = 4Ω, SE operation, both channels driven and loaded (average shown), POUT = 2.5W, AV = 1 Figure 4. THD+N vs Frequency THD+N vs Output Power VDD = 12V, RL = 8Ω, SE operation, both channels driven and loaded (average shown), POUT = 1W, AV = 1 Figure 5. VDD = 14.4V, RL = 4Ω, SE operation, AV = 1 single channel driven/single channel measured, fIN = 1kHz Figure 6. THD+N vs Output Power VDD = 12V, RL = 4Ω, SE operation, AV = 1 single channel driven/single channel measured, fIN = 1kHz Figure 7. 6 THD+N vs Output Power VDD = 12V, RL = 8Ω, SE operation, AV = 1 single channel driven/single channel measured, fIN = 1kHz Figure 8. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 LM4940 www.ti.com SNAS219C – OCTOBER 2003 – REVISED MAY 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) THD+N vs Output Power THD+N vs Output Power VDD = 12V, RL = 16Ω, SE operation, AV = 1 single channel driven/single channel measured, fIN = 1kHz Figure 9. VDD = 12V, RL = 4Ω, SE operation, AV = 10 single channel driven/single channel measured, fIN = 1kHz Figure 10. THD+N vs Output Power THD+N vs Output Power VDD = 12V, RL = 8Ω, SE operation, AV = 10 single channel driven/single channel measured, fIN = 1kHz Figure 11. VDD = 12V, RL = 16Ω, SE operation, AV = 10 single channel driven/single channel measured, fIN = 1kHz Figure 12. Output Power vs Power Supply Voltage RL = 4Ω, SE operation, fIN = 1kHz, both channels driven and loaded (average shown), at (from top to bottom at 12V): THD+N = 10%, THD+N = 1% Figure 13. Output Power vs Power Supply Voltage RL = 8Ω, SE operation, fIN = 1kHz, both channels driven and loaded (average shown), at (from top to bottom at 12V): THD+N = 10%, THD+N = 1% Figure 14. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 7 LM4940 SNAS219C – OCTOBER 2003 – REVISED MAY 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) Output Power vs Power Supply Voltage RL = 16Ω, SE operation, fIN = 1kHz, both channels driven and loaded (average shown), at (from top to bottom at 12V): THD+N = 10%, THD+N = 1% Figure 15. VDD = 12V, RL = 8Ω, SE operation, VRIPPLE = 200mVp-p, at (from top to bottom at 60Hz): CBYPASS = 1µF, CBYPASS = 4.7µF, CBYPASS = 10µF Figure 16. Power Supply Rejection vs Frequency Output Power vs Load Resistance 8 Total Power Dissipation vs Load Dissipation VDD = 12V, SE operation, fIN = 1kHz, at (from top to bottom at 1W): RL = 4Ω, RL = 8Ω Figure 18. VDD = 12V, RL = 8Ω, SE operation, VRIPPLE = 200mVp-p, AV = 10, at (from top to bottom at 60Hz): CBYPASS = 1µF, CBYPASS = 4.7µF, CBYPASS = 10µF Figure 17. VDD = 12V, SE operation, fIN = 1kHz, both channels driven and loaded, at (from top to bottom at 15Ω): THD+N = 10%, THD+N = 1% Figure 19. Power Supply Rejection vs Frequency Channel-to-Channel Crosstalk vs Frequency VDD = 12V, RL = 4Ω, POUT = 1W, SE operation, at (from top to bottom at 1kHz): VINB driven, VOUTA measured; VINA driven, VOUTB measured Figure 20. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 LM4940 www.ti.com SNAS219C – OCTOBER 2003 – REVISED MAY 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) Channel-to-Channel Crosstalk vs Frequency Power Supply Current vs Power Supply Voltage RL = 4Ω, SE operation VIN = 0V, RSOURCE = 50Ω VDD = 12V, RL = 8Ω, POUT = 1W, SE operation, at (from top to bottom at 1kHz): VINB driven, VOUTA measured; VINA driven, VOUTB measured Figure 21. Figure 22. Clipping Voltage vs Power Supply Voltage RL = 4Ω, SE operation, fIN = 1kHz both channels driven and loaded, at (from top to bottom at 13V): negative signal swing, positive signal swing Figure 23. Clipping Voltage vs Power Supply Voltage RL = 8Ω, SE operation, fIN = 1kHz both channels driven and loaded, at (from top to bottom at 13V): negative signal swing, positive signal swing Figure 24. Power Dissipation vs Ambient Temperature VDD = 12V, RL = 8Ω (SE), fIN = 1kHz, (from top to bottom at 120°C): 16in2 copper plane heatsink area, 8in2 copper plane heatsink area Figure 25. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 9 LM4940 SNAS219C – OCTOBER 2003 – REVISED MAY 2013 www.ti.com APPLICATION INFORMATION Figure 26. Typical LM4940 Stereo Amplifier Application Circuit HIGH VOLTAGE BOOMER WITH INCREASED OUTPUT POWER Unlike previous 5V Boomer amplifiers, the LM4940 is designed to operate over a power supply voltages range of 10V to 15V. Operating on a 12V power supply, the LM4940 will deliver 3.1W per channel into 4Ω loads with no more than 1% THD+N. POWER DISSIPATION Power dissipation is a major concern when designing a successful single-ended amplifier. Equation 1 states the maximum power dissipation point for a single-ended amplifier operating at a given supply voltage and driving a specified output load. PDMAX-SE = (VDD) 2/ (2π2RL): Single Ended (1) The LM4940's dissipation is twice the value given by Equation 1 when driving two SE loads. For a 12V supply and two 8Ω SE loads, the LM4940's dissipation is 1.82W. The maximum power dissipation point (twice the value given by Equation 1 must not exceed the power dissipation given by Equation 2: PDMAX' = (TJMAX - TA) / θJA (2) The LM4940's TJMAX = 150°C. In the KTW package, the LM4940's θJA is 20°C/W when the metal tab is soldered to a copper plane of at least 16in2. This plane can be split between the top and bottom layers of a two-sided PCB. Connect the two layers together under the tab with a 5x5 array of vias. For the NEC package, use an external heatsink with a thermal impedance that is less than 20°C/W. At any given ambient temperature TA, use Equation 3 to find the maximum internal power dissipation supported by the IC packaging. Rearranging Equation 3 and substituting PDMAX for PDMAX' results in Equation 4. This equation gives the maximum ambient temperature that still allows maximum stereo power dissipation without violating the LM4940's maximum junction temperature. 10 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 LM4940 www.ti.com SNAS219C – OCTOBER 2003 – REVISED MAY 2013 TA = TJMAX - PDMAX-SEθJA (3) For a typical application with a 12V power supply and two 4Ω SE loads, the maximum ambient temperature that allows maximum stereo power dissipation without exceeding the maximum junction temperature is approximately 113°C for the KTW package. TJMAX = PDMAX-SEθJA + TA (4) Equation 4 gives the maximum junction temperature TJMAX. If the result violates the LM4940's 150°C, reduce the maximum junction temperature by reducing the power supply voltage or increasing the load resistance. Further allowance should be made for increased ambient temperatures. The above examples assume that a device is operating around the maximum power dissipation point. Since internal power dissipation is a function of output power, higher ambient temperatures are allowed as output power or duty cycle decreases. If the result of Equation 3 is greater than that of Equation 4, then decrease the supply voltage, increase the load impedance, or reduce the ambient temperature. Further, ensure that speakers rated at a nominal 4Ω do not fall below 3Ω. If these measures are insufficient, a heat sink can be added to reduce θJA. The heat sink can be created using additional copper area around the package, with connections to the ground pins, supply pin and amplifier output pins. Refer to the TYPICAL PERFORMANCE CHARACTERISTICS curves for power dissipation information at lower output power levels. POWER SUPPLY VOLTAGE LIMITS Continuous proper operation is ensured by never exceeding the voltage applied to any pin, with respect to ground, as listed in the Absolute Maximum Ratings section. POWER SUPPLY BYPASSING As with any power amplifier, proper supply bypassing is critical for low noise performance and high power supply rejection. Applications that employ a voltage regulator typically use a 10µF in parallel with a 0.1µF filter capacitors to stabilize the regulator's output, reduce noise on the supply line, and improve the supply's transient response. However, their presence does not eliminate the need for a local 1.0µF tantalum bypass capacitance connected between the LM4940's supply pins and ground. Do not substitute a ceramic capacitor for the tantalum. Doing so may cause oscillation. Keep the length of leads and traces that connect capacitors between the LM4940's power supply pin and ground as short as possible. Connecting a 10µF capacitor, CBYPASS, between the BYPASS pin and ground improves the internal bias voltage's stability and improves the amplifier's PSRR. The PSRR improvements increase as the bypass pin capacitor value increases. Too large, however, increases turn-on time and can compromise the amplifier's click and pop performance. The selection of bypass capacitor values, especially CBYPASS, depends on desired PSRR requirements, click and pop performance (as explained in the section, SELECTING EXTERNAL COMPONENTS), system cost, and size constraints. MICRO-POWER SHUTDOWN The LM4940 features an active-low shutdown mode that disables the amplifier's bias circuitry, reducing the supply current to 40μA (typ). Connect SHUTDOWN to a voltage between 2V to VDD/2 for normal operation. Connect SHUTDOWN to GND to disable the device. A voltage that is greater than GND can increase shutdown current. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 11 LM4940 SNAS219C – OCTOBER 2003 – REVISED MAY 2013 www.ti.com SELECTING EXTERNAL COMPONENTS Input Capacitor Value Selection Two quantities determine the value of the input coupling capacitor: the lowest audio frequency that requires amplification and desired output transient suppression. As shown in Figure 26, the input resistor (RIN) and the input capacitor (CIN) produce a high pass filter cutoff frequency that is found using Equation 5. fC = 1/2πRiCi (5) As an example when using a speaker with a low frequency limit of 50Hz, Ci, using Equation 5 is 0.159µF. The 0.39µF CINA shown in Figure 26 allows the LM4940 to drive high efficiency, full range speaker whose response extends below 30Hz. Output Coupling Capacitor Value Selection The capacitors COUTA and COUTB that block the VDD/2 output DC bias voltage and couple the output AC signal to the amplifier loads also determine low frequency response. These capacitors, combined with their respective loads create a highpass filter cutoff frequency. The frequency is also given by Equation 5. Using the same conditions as above, with a 4Ω speaker, COUT is 820µF (nearest common valve). Bypass Capacitor Value Besides minimizing the input capacitor size, careful consideration should be paid to value of CBYPASS, the capacitor connected to the BYPASS pin. Since CBYPASS determines how fast the LM4940 settles to quiescent operation, its value is critical when minimizing turn-on pops. The slower the LM4940's outputs ramp to their quiescent DC voltage (nominally VDD/2), the smaller the turn-on pop. Choosing CBYPASS equal to 10µF along with a small value of CIN (in the range of 0.1µF to 0.39µF), produces a click-less and pop-less shutdown function. As discussed above, choosing CIN no larger than necessary for the desired bandwidth helps minimize clicks and pops. OPTIMIZING CLICK AND POP REDUCTION PERFORMANCE The LM4940 contains circuitry that eliminates turn-on and shutdown transients ("clicks and pops"). For this discussion, turn-on refers to either applying the power supply voltage or when the micro-power shutdown mode is deactivated. As the VDD/2 voltage present at the BYPASS pin ramps to its final value, the LM4940's internal amplifiers are configured as unity gain buffers and are disconnected from the AMPA and AMPB pins. An internal current source charges the capacitor connected between the BYPASS pin and GND in a controlled manner. Ideally, the input and outputs track the voltage applied to the BYPASS pin. The gain of the internal amplifiers remains unity until the voltage applied to the BYPASS pin. The gain of the internal amplifiers remains unity until the voltage on the bypass pin reaches VDD/2. As soon as the voltage on the bypass pin is stable, the device becomes fully operational and the amplifier outputs are reconnected to their respective output pins. Although the BYPASS pin current cannot be modified, changing the size of CBYPASS alters the device's turn-on time. Here are some typical turn-on times for various values of CBYPASS: 12 CB (µF) TON (ms) 1.0 120 2.2 120 4.7 200 10 440 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 LM4940 www.ti.com SNAS219C – OCTOBER 2003 – REVISED MAY 2013 In order eliminate "clicks and pops", all capacitors must be discharged before turn-on. Rapidly switching VDD may not allow the capacitors to fully discharge, which may cause "clicks and pops". There is a relationship between the value of CIN and CBYPASS that ensures minimum output transient when power is applied or the shutdown mode is deactivated. Best performance is achieved by setting the time constant created by CIN and Ri + Rf to a value less than the turn-on time for a given value of CBYPASS as shown in the table above. AUDIO POWER AMPLIFIER DESIGN Audio Amplifier Design: Driving 3W into a 4Ω load The following are the desired operational parameters: Power Output 3WRMS Load Impedance 4Ω Input Level 0.3VRMS (max) Input Impedance 20kΩ Bandwidth 100Hz–20kHz ± 0.25dB The design begins by specifying the minimum supply voltage necessary to obtain the specified output power. One way to find the minimum supply voltage is to use the Output Power vs Power Supply Voltage curve in the TYPICAL PERFORMANCE CHARACTERISTICS section. Another way, using Equation 6, is to calculate the peak output voltage necessary to achieve the desired output power for a given load impedance. To account for the amplifier's dropout voltage, two additional voltages, based on the Clipping Dropout Voltage vs Power Supply Voltage in the TYPICAL PERFORMANCE CHARACTERISTICS curves, must be added to the result obtained by Equation 6. The result is Equation 7. (6) VDD = VOUTPEAK + VODTOP + VODBOT (7) The Figure 13 graph for an 8Ω load indicates a minimum supply voltage of 11.8V. The commonly used 12V supply voltage easily meets this. The additional voltage creates the benefit of headroom, allowing the LM4940 to produce an output power of 3W without clipping or other audible distortion. The choice of supply voltage must also not create a situation that violates of maximum power dissipation as explained above in the POWER DISSIPATION section. After satisfying the LM4940's power dissipation requirements, the minimum differential gain needed to achieve 3W dissipation in a 4Ω BTL load is found using Equation 8. (8) Thus, a minimum gain of 11.6 allows the LM4940's to reach full output swing and maintain low noise and THD+N performance. For this example, let AV = 12. The amplifier's overall BTL gain is set using the input (RINA) and feedback (R) resistors of the first amplifier in the series BTL configuration. Additionaly, AV-BTL is twice the gain set by the first amplifier's RIN and Rf. With the desired input impedance set at 20kΩ, the feedback resistor is found using Equation 9. Rf/ RIN = AV (9) The value of Rf is 240kΩ. The nominal output power is 3W. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 13 LM4940 SNAS219C – OCTOBER 2003 – REVISED MAY 2013 www.ti.com The last step in this design example is setting the amplifier's -3dB frequency bandwidth. To achieve the desired ±0.25dB pass band magnitude variation limit, the low frequency response must extend to at least one-fifth the lower bandwidth limit and the high frequency response must extend to at least five times the upper bandwidth limit. The gain variation for both response limits is 0.17dB, well within the ±0.25dB-desired limit. The results are an fL = 100Hz / 5 = 20Hz (10) fL = 20kHz x 5 = 100kHz (11) and As mentioned in the SELECTING EXTERNAL COMPONENTS section, RINA and CINA, as well as COUT and RL, create a highpass filter that sets the amplifier's lower bandpass frequency limit. Find the coupling capacitor's value using Equation 14. CIN = 1 / 2πRINfL (12) The result is 1 / (2πx20kΩx20Hz) = 0.398µF = CIN (13) 1 / (2π x 4Ω x 20Hz) = 1989µF = COUT (14) and Use a 0.39µF capacitor for CIN and a 2000µF capacitor for COUT, the closest standard values. The product of the desired high frequency cutoff (100kHz in this example) and the differential gain AV, determines the upper passband response limit. With AV = 12 and fH = 100kHz, the closed-loop gain bandwidth product (GBWP) is 1.2mHz. This is less than the LM4940's 3.5MHz GBWP. With this margin, the amplifier can be used in designs that require more differential gain while avoiding performance restricting bandwidth limitations. RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT Figure 27 through Figure 29 show the recommended two-layer PC board layout that is optimized for the DDPAKpackaged LM4940 and associated external components. This circuit board is designed for use with an external 12V supply and 4Ω (min) speakers. This circuit board is easy to use. Apply 12V and ground to the board's VDD and GND pads, respectively. Connect a speaker between the board's OUTA and OUTB outputs and their respective GND terminals. 14 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 LM4940 www.ti.com SNAS219C – OCTOBER 2003 – REVISED MAY 2013 Demonstration Board Layout Figure 27. Recommended KTW PCB Layout: Top Silkscreen Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 15 LM4940 SNAS219C – OCTOBER 2003 – REVISED MAY 2013 www.ti.com Figure 28. Recommended KTW PCB Layout: Top Layer 16 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 LM4940 www.ti.com SNAS219C – OCTOBER 2003 – REVISED MAY 2013 Figure 29. Recommended KTW PCB Layout: Bottom Layer Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 17 LM4940 SNAS219C – OCTOBER 2003 – REVISED MAY 2013 www.ti.com REVISION HISTORY Changes from Revision B (May 2013) to Revision C • 18 Page Changed layout of National Data Sheet to TI format .......................................................................................................... 17 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM4940 PACKAGE OPTION ADDENDUM www.ti.com 10-Dec-2020 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) LM4940TS/NOPB ACTIVE DDPAK/ TO-263 KTW 9 45 RoHS-Exempt & Green SN Level-3-245C-168 HR -40 to 85 L4940TS LM4940TSX/NOPB ACTIVE DDPAK/ TO-263 KTW 9 500 RoHS-Exempt & Green SN Level-3-245C-168 HR -40 to 85 L4940TS (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of