LM4952TS

LM4952 3.1W Stereo-SE Stereo Audio Power Amplifier with DC Volume Control August 2004 LM4952 3.1W Stereo-SE Audio Power Amplifier with DC Volume Control General Description The LM4952 is a dual audio power amplifier primarily designed for demanding applications in flat panel monitors and TV’s. It is capable of delivering 3.1 watts per channel to a 4Ω single-ended load with less than 1% THD+N when powered by a 12VDC power supply. Eliminating external feedback resistors, an internal, DCcontrolled, volume control allows easy and variable gain adjustment. Boomer audio power amplifiers were designed specifically to provide high quality output power with a minimal amount of external components. The LM4952 does not require bootstrap capacitors or snubber circuits. Therefore, it is ideally suited for display applications requiring high power and minimal size. The LM4952 features a low-power consumption active-low shutdown mode. Additionally, the LM4952 features an internal thermal shutdown protection mechanism along with short circuit protection. The LM4952 contains advanced pop & click circuitry that eliminates noises which would otherwise occur during turn-on and turn-off transitions. Key Specifications j Quiscent Power Supply Current j POUT 18mA (typ) 3.8W (typ) 55µA (typ) VDD = 12V, RL = 4Ω, 10% THD+N j Shutdown current Features n Pop & click circuitry eliminates noise during turn-on and turn-off transitions n Low current, active-low shutdown mode n Low quiescent current n Stereo 3.8W output, RL = 4Ω n DC-controlled volume control n Short circuit protection Applications n Flat Panel Monitors n Flat panel TV’s n Computer Sound Cards Connection Diagram 200809E9 Top View Order Number LM4952TS See NS Package Number TS9A U = Wafer Fab Code Z = Assembly Plant Code XY = Date Coce TT = Die Traceability L4952TS = LM4952TS Boomer ® is a registered trademark of National Semiconductor Corporation. © 2004 National Semiconductor Corporation DS200809 www.national.com LM4952 Typical Application 200809E8 FIGURE 1. Typical LM4952 SE Audio Amplifier Application Circuit www.national.com 2 LM4952 Absolute Maximum Ratings (Notes 1, 2) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (pin 6, referenced to GND, pins 4 and 5) Storage Temperature Input Voltage pins 4, 6, and 7 pins 1, 2, 3, 8, and 9 Power Dissipation (Note 3) ESD Susceptibility (Note 4) −0.3V to VDD + 0.3V −0.3V to 9.5V Internally limited 2000V 18.0V −65˚C to +150˚C ESD Susceptibility (Note 5) Junction Temperature Thermal Resistance θJC (TS) θJA (TS) (Note 3) 200V 150˚C 4˚C/W 20˚C/W Operating Ratings Temperature Range TMIN ≤ TA ≤ TMAX Supply Voltage −40˚C ≤ T A ≤ 85˚C 9.6V ≤ VDD ≤ 16V Electrical Characteristics VDD = 12V (Notes 1, 2) Symbol Parameter The following specifications apply for VDD = 12V, AV = 20dB (nominal), RL = 4Ω, and TA = 25˚C unless otherwise noted. Conditions LM4952 Typical (Note 6) IDD ISD RIN VIN VSDIH VSDIL TWU TSD PO Quiescent Power Supply Current Shutdown Current Amplifier Input Resistance Amplifier Input Signal Shutdown Voltage Input High Shutdown Voltage Input Low Wake-up Time Thermal Shutdown Temperature Output Power f = 1kHz, THD+N = 1% THD+N = 10% PO = 2.0Wrms, f = 1kHz A-Weighted Filter, VIN = 0V, Input Referred fIN = 1kHz, PO = 1W, Input Referred RL = 8Ω RL = 4Ω VRIPPLE = 200mVp-p, f = 1kHz, Input Referred VIN = 0V, RL = 500mΩ CB = 4.7µF 440 170 3.1 3.8 0.08 8 2.8 VIN = 0V, IO = 0A, No Load VSHUTDOWN = GND (Note 9) VDC VDC VOL VOL Limit (Notes 7, 8) 35 85 Units (Limits) mA (max) µA (max) kΩ kΩ 18 55 44 200 = VDD/2 = GND VDD/2 2.0 VDD/2 0.4 Vp-p (max) V (min) V (max) V (max) ms ˚C W (min) % µV THD+N eOS XTALK Total Harmomic Distortion + Noise Output Noise Channel Separation 78 72 89 5 80 dB dB (min) A PSRR IOL Power Supply Rejection Ratio Output Current Limit 3 www.national.com LM4952 Electrical Characteristics for Volume Control (Notes 1, 2) The following specifications apply for VDD = 12V, AV = 20dB (nominal), and TA = 25˚C unless otherwise noted. LM4952 Symbol VOLmax VOLmin AM Gain Gain Mute Attenuation Parameter Conditions VDC-VOL = Full scale, No Load VDC-VOL = +1LSB, No Load VDC-VOL = 0V, No Load Typical (Note 6) 20 -46 75 63 Limit (Note 7) Units (Limits) dB dB dB (min) Note 1: All voltages are measured with respect to the GND pin, unless otherwise specified. Note 2: 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 guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device performance. Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature, TA. The maximum allowable power dissipation is PDMAX = (TJMAX − TA) / θJA or the given in Absolute Maximum Ratings, whichever is lower. For the LM4952 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 the TO263 package mounted to 16in2 heatsink surface area. Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor. Note 5: Machine Model, 220pF–240pF discharged through all pins. Note 6: Typicals are measured at 25˚C and represent the parametric norm. Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Note 8: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis. Note 9: 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. External Components Description Components 1. CIN Refer to Figure 1 Functional Description 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, for an explanation of determining CIN’s value. The supply bypass capacitor. Refer to the POWER SUPPLY BYPASSING section for information about properly placing, and selecting the value of, this capacitor. This capacitor filters the half-supply voltage present on the BYPASS pin. Refer to the Application section, SELECTING EXTERNAL COMPONENTS, for information about properly placing, and selecting the value of, this capacitor. 2. CS 3. CBYPASS www.national.com 4 LM4952 Typical Performance Characteristics THD+N vs Frequency AV = 20dB and TA = 25˚C, unless otherwise noted. THD+N vs Frequency 200809F8 200809F9 VDD = 12V, RL = 4Ω, POUT = 2W, CIN = 1.0µF THD+N vs Output Power VDD = 12V, RL = 8Ω, POUT = 1W, CIN = 1.0µF THD+N vs Output Power 200809G0 200809G1 VDD = 12V, RL = 4Ω, fIN = 1kHz VDD = 12V, RL = 8Ω, fIN = 1kHz 5 www.national.com LM4952 Typical Performance Characteristics AV = 20dB and TA = 25˚C, unless otherwise noted. (Continued) Output Power vs Power Supply Voltage Output Power vs Power Supply Voltage 20080910 20080909 RL = 4Ω, fIN = 1kHz both channels driven and loaded (average shown), at (from top to bottom at 12V): THD+N = 10%, THD+N = 1% Power Supply Rejection vs Frequency RL = 8Ω, fIN = 1kHz both channels driven and loaded (average shown), at (from top to bottom at 12V): THD+N = 10%, THD+N = 1% Total Power Dissipation vs Load Dissipation 20080913 200809F7 VDD = 12V, RL = 4Ω, VRIPPLE = 200mVp-p Output Power vs Load Resistance VDD = 12V, fIN = 1kHz, at (from top to bottom at 1W): RL = 4Ω, RL = 8Ω Channel-to-Channel Crosstalk vs Frequency 20080914 VDD = 12V, fIN = 1kHz, at (from top to bottom at 15Ω): THD+N = 10%, THD+N = 1% 20080915 VDD = 12V, RL = 4Ω, POUT = 1W, Input Referred at (from top to bottom at 1kHz): VINB driven, VOUTA measured, VINA driven, VOUTB measured www.national.com 6 LM4952 Typical Performance Characteristics AV = 20dB and TA = 25˚C, unless otherwise noted. (Continued) Channel-to-Channel Crosstalk vs Frequency Amplifier Gain vs DC Volume Voltage 20080916 200809F5 VDD = 12V, RL = 8Ω, POUT = 1W, Input Referred at (from top to bottom at 1kHz): VINB driven, VOUTA measured, VINA driven, VOUTB measured Amplifier Gain vs Part-to-Part DC Volume Voltage Variation (Five parts) VDD = 12V, RL = 8Ω, at (from top to bottom at 1.5V): Decreasing DC Volume Voltage, Increasing DC Volume Voltage THD+N vs Frequency 200809F6 VDD = 12V, RL = 8Ω, 200809G2 VDD = 9.6V, RL = 4Ω, POUT = 1.1W, CIN = 1.0µF THD+N vs Frequency THD+N vs Output Power 200809G3 VDD = 9.6V, RL = 8Ω, POUT = 850mW, CIN = 1.0µF 200809G4 VDD = 9.6V, RL = 4Ω, fIN = 1kHz 7 www.national.com LM4952 Typical Performance Characteristics AV = 20dB and TA = 25˚C, unless otherwise noted. (Continued) THD+N vs Output Power Total Power Dissipation vs Load Dissipation 20080919 200809G5 VDD = 9.6V, RL = 8Ω, fIN = 1kHz Output Power vs Load Resistance VDD = 9.6V, fIN = 1kHz at (from top to bottom at 1W): RL = 4Ω, RL = 8Ω Power Supply Rejection vs Frequency 20080920 VDD = 9.6V, fIN = 1kHz, at (from top to bottom at 15Ω): THD+N = 10%, THD+N = 1% 200809G6 VDD = 9.6V, RL = 4Ω, VRIPPLE = 200mVP-P Channel-to Channel Crosstalk vs Frequency Channel-to Channel Crosstalk vs Frequency 20080921 VDD = 9.6V, RL = 4Ω, POUT = 1W, Input Referred at (from top to bottom at 1kHz): VINB driven, VOUTA measured; VINA driven, VOUTB measured 20080922 VDD = 9.6V, RL = 8Ω, POUT = 1W, Input Referred at (from top to bottom at 1kHz): VINB driven, VOUTA measured; VINA driven, VOUTB measured www.national.com 8 LM4952 Typical Performance Characteristics AV = 20dB and TA = 25˚C, unless otherwise noted. (Continued) THD+N vs Frequency THD+N vs Frequency 200809G7 200809G8 VDD = 14V, RL = 4Ω, POUT = 2W, CIN = 1.0µF THD+N vs Output Power VDD = 14V, RL = 8Ω, POUT = 1W, CIN = 1.0µF THD+N vs Output Power 200809G9 200809H0 VDD = 14V, RL = 4Ω, fIN = 1kHz Power Supply Rejection vs Frequency VDD = 14V, RL = 8Ω fIN = 1kHz Output Power vs Load Resistance 20080925 200809H1 VDD = 14V, RL = 4Ω VRIPPLE = 200mVP-P VDD = 15V, fIN = 1kHz, at (from top to bottom at 2W): RL = 4Ω, RL = 8Ω 9 www.national.com LM4952 Typical Performance Characteristics AV = 20dB and TA = 25˚C, unless otherwise noted. (Continued) THD+N vs Output Power THD+N vs Output Power 20080926 VDD = 15V, at (from top to bottom at 15Ω): THD+N = 10%, THD+N = 1%, fIN = 1kHz 20080927 VDD = 16V, RL = 4Ω, fIN = 1kHz Channel-to-Channel Crosstalk vs Frequency Channel-to-Channel Crosstalk vs Frequency 20080928 VDD = 16V, RL = 4Ω, POUT = 1W, Input Referred at (from top to bottom at 1kHz): VINB driven, VOUTA measured; VINA driven, VOUTB measured Power Supply Current vs Power Supply Voltage 20080929 VDD = 16V, RL = 8Ω, POUT = 1W, Input Referred at (from top to bottom at 1kHz): VINB driven, VOUTA measured; VINA driven, VOUTB measured Clipping Voltage vs Power Supply Voltage 200809H2 20080931 VIN RL = 4Ω, = 0V, RSOURCE = 50Ω RL = 4Ω, fIN = 1kHz at (from top to bottom at 12.5V): positive signal swing, negative signal swing www.national.com 10 LM4952 Typical Performance Characteristics AV = 20dB and TA = 25˚C, unless otherwise noted. (Continued) Clipping Voltage vs Power Supply Voltage Power Dissipation vs Ambient Temperature 20080933 20080932 RL = 8Ω, fIN = 1kHz at (from to bottom at 12.5V): positive signal swing, negative signal swing Power Dissipation vs Ambient Temperature VDD = 12V, RL = 4Ω (SE), fIN = 1kHz, (from to bottom at 80˚C): 16in2 copper plane heatsink area, 8in2 copper plane heatsink area 20080934 VDD = 12V, RL = 8Ω, fIN = 1kHz, (from to bottom at 120˚C): 16in2 copper plane heatsink area, 8in2 copper plane heatsink area 11 www.national.com LM4952 Application Information HIGH VOLTAGE BOOMER WITH INCREASED OUTPUT POWER 200809E8 FIGURE 2. Typical LM4952 SE Application Circuit Unlike previous 5V Boomer ® amplifiers, the LM4952 is designed to operate over a power supply voltages range of 9.6V to 16V. Operating on a 12V power supply, the LM4952 will deliver 3.8W into a 4Ω SE load with no more than 10% THD+N. POWER DISSIPATION Power dissipation is a major concern when successful single-ended or bridged amplifier. states the maximum power dissipation point ended amplifier operating at a given supply driving a specified output load. PDMAX-SE = (VDD) 2 designing a Equation (2) for a singlevoltage and tween the top and bottom layers of a two-sided PCB. Connect the two layers together under the tab with a 5x5 array of vias. At any given ambient temperature TA, use Equation (2) to find the maximum internal power dissipation supported by the IC packaging. Rearranging Equation (2) and substituting PDMAX for PDMAX’ results in Equation (3). This equation gives the maximum ambient temperature that still allows maximum stereo power dissipation without violating the LM4952’s maximum junction temperature. TA = TJMAX - PDMAX-SEθJA (3) / (2π2RL): Single Ended (1) The LM4952’s dissipation is twice the value given by Equation (2) when driving two SE loads. For a 12V supply and two 4Ω SE loads, the LM4952’s dissipation is 1.82W. The maximum power dissipation point given by Equation (1) must not exceed the power dissipation given by Equation (2): PDMAX’ = (TJMAX - TA) / θJA (2) For a typical application with a 12V power supply and an SE 4Ω load, the maximum ambient temperature that allows maximum stereo power dissipation without exceeding the maximum junction temperature is approximately 77˚C for the TS package. TJMAX = PDMAX-MONOBTLθJA + TA (4) The LM4952’s TJMAX = 150˚C. In the TS package, the LM4952’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 bewww.national.com 12 Equation (4) gives the maximum junction temperature TJMAX. If the result violates the LM4952’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 LM4952 Application Information (Continued) 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 (1) is greater than that of Equation (2), 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 10µF tantalum bypass capacitance connected between the LM4952’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 LM4952’s power supply pin and ground as short as possible. BYPASS PIN BYPASSING Connecting a 4.7µF 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. 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 LM4952 features an active-low micro-power shutdown mode. When active, the LM4952’s micro-power shutdown feature turns off the amplifier’s bias circuitry, reducing the supply current. The low 55µA typical shutdown current is achieved by applying a voltage to the SHUTDOWN pin that is as near to GND as possible. A voltage that is greater than GND may increase the shutdown current. There are a few methods to control the micro-power shutdown. These include using a single-pole, single-throw switch (SPST), a microprocessor, or a microcontroller. Figure 3 shows a simple switch-based circuit that can be used to control the LM4952’s shutdown fucntion. Select normal amplifier operation by closing the switch. Opening the switch applies GND to the SHUTDOWN pin, activating micro-power shutdown. The switch and resistor guarantee that the SHUTDOWN pin will not float. This prevents unwanted state changes. In a system with a microprocessor or a microcontroller, use a digital output to apply the active-state voltage to the SHUTDOWN pin. 200809H3 FIGURE 3. Simple switch and voltage divider generates shutdown control signal DC VOLUME CONTROL The LM4952 has an internal stereo volume control whose setting is a function of the DC voltage applied to the DC VOL input pin. The LM4952 volume control consists of 31 steps that are individually selected by a variable DC voltage level on the volume control pin. As shown in Figure 4, the range of the steps, controlled by the DC voltage, is 20dB to -46dB. The gain levels are 1dB/step from 20dB to 14dB, 2dB/step from 14dB to -16dB, 3dB/step from -16dB to -27dB, 4dB/step from -27db to -31dB, 5dB/step from -31dB to -46dB. 200809F5 FIGURE 4. Volume control response Like all volume controls, the LM4952’s internal volume control is set while listening to an amplified signal that is applied to an external speaker. The actual voltage applied to the DC VOL input pin is a result of the volume a listener desires. As such, the volume control is designed for use in a feedback system that includes human ears and preferences. This feedback system operates quite well without the need for accurate gain. The user simply sets the volume to the desired level as determined by their ear, without regard to the actual DC voltage that produces the volume. Therefore, the accuracy of the volume control is not critical, as long as volume changes monotonically and step size is small enough to reach a desired volume that is not too loud or too 13 www.national.com LM4952 Application Information (Continued) soft. Since the gain is not critical, there may be a volume variation from part-to-part even with the same applied DC volume control voltage. The gain of a given LM4952 can be set with fixed external voltage, but another LM4952 may require a different control voltage to achieve the same gain. Figure 5 is a curve showing the volume variation of five typical LM4952s as the voltage applied to the DC VOL input pin is varied. For gains between –20dB and +16dB, the typical part-to-part variation is typically ± 1dB for a given control voltage. 20080966 FIGURE 6. Typical circuit used for DC voltage volume control. Capacitor connected to DC VOL pin minimizes voltage fluctuation when using unregulated supplies that could cause changes in perceived volume setting UNREGULATED POWER SUPPLIES AND THE DC VOL CONTROL As an amplifier’s output power increases, the current that flows from the power supply also increases. If an unregulated power supply is used, its output voltage can decrease (“droop” or “sag”) as this current increases. It is not uncommon for an unloaded unregulated 15V power supply connected to the LM4952 to sag by as much as 2V when the amplifier is drawing 1A to 2A while driving 4Ω stereo loads to full power dissipation. Figure 7 is an oscilloscope photo showing an unregulated power supply’s voltage sag while powering an LM4952 that is driving 4Ω stereo loads. The amplifier’s input is a typical music signal supplied by a CD player. As shown, the sag can be quite significant. 200809F6 FIGURE 5. Typical part-to-part gain variation as a function of DC Vol control voltage VOLUME CONTROL VOLTAGE GENERATION Figure 6 shows a simple circuit that can be used to create an adjustable DC control voltage that is applied to the DC Vol input. The 91kΩ series resistor and the 50kΩ potentiometer create a voltage divider between the supply voltage, VDD, and GND. The series resistor’s value assumes a 12V power supply voltage. The voltage present at the node between the series resistor and the top of the potentiometer need only be a nominal value of 3.5V and must not exceed 9.5V, as stated in the LM4952’s Absolute Maximum Ratings. 20080968 FIGURE 7. LM4952 operating on an unregulated 12V (nominal) power supply. Wave forms shown include VDD (Trace A), VOUT A (Trace B), VOUT B (Trace C), and the DC voltage applied to the DC VOL pin (Trace D) This sagging supply voltage presents a potential problem when the voltage that drives the DC Vol pin is derived from the voltage supplied by an unregulated power supply. This is the case for the typical volume control circuit (a 50kΩ potentiometer in series with a 91kΩ resistor) shown in Figure 6. The potentiometer’s wiper is connected to the DC Vol pin. With this circuit, power supply voltage fluctuations will be www.national.com 14 LM4952 Application Information (Continued) seen by the DC Vol input. Though attenuated by the voltage divider action of the potentiometer and the series resistor, these fluctuations may cause perturbations in the perceived volume. An easy and simple solution that suppresses these perturbations is a 10µF capacitor connected between the DC Vol pin and ground. See the result of this capacitor in Figure 8. This capacitance can also be supplemented with bulk capacitance in the range of 1000µF to 10,000µF connected to the unregulated power supply’s output. Figure 10 shows how this bulk capacitance minimizes fluctuations on VDD. 20080970 FIGURE 10. Same conditions and waveforms as shown in Figure 8, except that a 4700µF capacitor has been connected between the VDD pin and GND (Trace A) 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. The amplifier’s input resistance and the input capacitor (CIN) produce a high pass filter cutoff frequency that is found using Equation (5). (5) FCIN = 1/(2πRINCIN) As an example when using a speaker with a low frequency limit of 50Hz and based on the LM4952’s 44kΩ nominal minimum input resistance, CIN, using Equation (5) is 0.072µF. The 0.39µF CINA shown in Figure 2 allows the LM4952 to drive high efficiency, full range speaker whose response extends below 30Hz. Similarly, the output coupling capacitor and the load impedance also form a high pass filter. The cutoff frequency formed by these two components is found using Equation (6) (6) fCOUT = 1/(2πRLOADCOUT) Expanding on the example above and assuming a nominal speaker impedance of 4Ω, response below 30Hz is assured if the output coupling capacitors have a value, using Equation (6), greater than 1330µF. 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 LM4952 settles to quiescent operation, its value is critical when minimizing turn-on pops. The slower the LM4952’s outputs ramp to their quiescent DC voltage (nominally VDD/2), the smaller the turn-on pop. Choosing CBYPASS equal to 4.7µF 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. Routing Input and BYPASS Capacitor Grounds Optimizing the LM4952’s low distortion performance is easily accomplished by connecting the input signal’s ground reference directly to the TO263’s grounded tab connection. In like 15 www.national.com 20080969 FIGURE 8. Same conditions and waveforms as shown in Figure 7, except that a 10µF capacitor has been connected between the DC VOL pin and GND (Trace D) If space constraints preclude the use of a 10µF capacitor connected to the DC Vol pin or large amounts of bulk supply capacitance, or if more resistance to the fluctuations is desired, using an LM4040-4.1 voltage reference shown in Figure 9 is recommended. The value of the 91kΩ resistor, already present in the typical volume applications circuit, should be changed to 62kΩ. This sets the LM4040-4.1’s bias current at 125µA when using a nominal 12V supply, well within the range of current needed by this reference. 20080967 FIGURE 9. Using an LM4040–4.1 to set the maximum DC volume control voltage and attenuate power supply variations when using unregulated supplies that would otherwise perturb the volume setting. LM4952 Application Information (Continued) manner, the ground lead of the capacitor connected between the BYPASS pin and GND should also be connected to the package’s grounded tab. OPTIMIZING CLICK AND POP REDUCTION PERFORMANCE The LM4952 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/4 voltage present at the BYPASS pin ramps to its final value, the LM4952’s internal amplifiers are muted. Once the voltage at the BYPASS pin reaches VDD/4, the amplifiers are unmuted. The gain of the internal amplifiers remains unity until the voltage on the bypass pin reaches VDD/4. 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. 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 selecting a CBYPASS value that is greater than twelve times CIN’s value. RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT Figure 9 through Figure 11 show the recommended twolayer PC board layout that is optimized for the TO263packaged, SE-configured LM4952 and associated external components. These circuits are designed for use with an external 12V supply and 4Ω(min)(SE) speakers. These circuit boards are 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 respective GND pins. www.national.com 16 LM4952 Demonstration Board Layout 200809F2 FIGURE 11. Recommended TS SE PCB Layout: Top Silkscreen 200809F4 FIGURE 12. Recommended TS SE PCB Layout: Top Layer 17 www.national.com LM4952 Demonstration Board Layout (Continued) 200809F3 FIGURE 13. Recommended TS SE PCB Layout: Bottom Layer www.national.com 18 LM4952 Physical Dimensions unless otherwise noted inches (millimeters) Order Number LM4952TS NS Package Number TS9A 19 www.national.com LM4952 3.1W Stereo-SE Stereo Audio Power Amplifier with DC Volume Control Notes LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. BANNED SUBSTANCE COMPLIANCE National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2. National Semiconductor Americas Customer Support Center Email: new.feedback@nsc.com Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: ap.support@nsc.com National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: jpn.feedback@nsc.com Tel: 81-3-5639-7560 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.