LM4898 1 Watt Fully Differential Audio Power Amplifier With Shutdown Select General Description Key Specifications The LM4898 is a fully differential audio power amplifier primarily designed for demanding applications in mobile phones and other portable communication device applications. It is capable of delivering 1 watt of continuous average power to an 8Ω BTL load with less than 1% distortion (THD+N) from a 5VDC power supply. Boomer audio power amplifiers were designed specifically to provide high quality output power with a minimal amount of external components. The LM4898 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 LM4898 features a low-power consumption shutdown mode. To facilitate this, Shutdown may be enabled by either logic high or low depending on mode selection. Driving the shutdown mode pin either high or low enables the shutdown select pin to be driven in a likewise manner to enable Shutdown. Additionally, the LM4898 features an internal thermal shutdown protection mechanism. The LM4898 contains advanced pop & click circuitry which virtually eliminates noises which would otherwise occur during turn-on and turn-off transitions. j Improved PSRR at 217Hz 83dB(typ) j Power Output at 5.0V & 1% THD 1.0W(typ) j Power Output at 3.3V & 1% THD 400mW(typ) j Shutdown Current 0.1µA(typ) Features n Fully differential amplification n Available in space-saving packages micro SMD, MSOP, and LLP n Ultra low current shutdown mode n Can drive capacitive loads up to 500pF n Improved pop & click circuitry eliminates noises during turn-on and turn-off transitions n 2.4 - 5.5V operation n No output coupling capacitors, snubber networks or bootstrap capacitors required n Shutdown high or low selectivity Applications n Mobile phones n PDAs n Portable electronic devices Connection Diagrams Mini Small Outline (MSOP) Package MSOP Marking 20073723 Top View Order Number LM4898MM See NS Package Number MUB10A 20073774 Z -Assembly Code X - Date Code TT - Die Run Traceability G - Boomer Family B3 - LM4898MM Boomer ® is a registered trademark of National Semiconductor Corporation. © 2003 National Semiconductor Corporation DS200737 www.national.com LM4898 1 Watt Fully Differential Audio Power Amplifier With Shutdown Select July 2003 LM4898 Connection Diagrams (Continued) LLP Package LD Marking 20073756 Top View Order Number LM4898LD See NS Package Number LDA10B Z- Assembly Code XY - Date Code TT - Die Run Traceability L4898 - LM4898LD 9 Bump micro SMD Package 9 Bump micro SMD Marking 20073735 20073784 X - Date Code T - Die Run Traceability G - Boomer Family C3 - LM4898ITLX 20073736 Top View Order Number LM4898ITL, LM4898ITLX See NS Package Number TLA09AAA www.national.com 2 LM4898 Typical Application 20073701 FIGURE 1. Typical Audio Amplifier Application Circuit 3 www.national.com LM4898 Absolute Maximum Ratings θJA (LLP) (Note 2) θJA (micro SMD) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage 6.0V Storage Temperature Power Dissipation (Note 3) Internally Limited ESD Susceptibility (Note 4) 2000V ESD Susceptibility (Note 5) 200V Junction Temperature 56˚C/W θJA (MSOP) 190˚C/W See AN-1112 "microSMD Wafers Level Chip Scale Package." Operating Ratings Temperature Range 150˚C TMIN ≤ TA ≤ TMAX Thermal Resistance θJC (LLP) 220˚C/W θJC (MSOP) Soldering Information −65˚C to +150˚C −0.3V to VDD +0.3V Input Voltage 63˚C/W −40˚C ≤ TA ≤ 85˚C 2.4V ≤ VDD ≤ 5.5V Supply Voltage 12˚C/W Electrical Characteristics VDD = 5V (Notes 1, 2, 8) The following specifications apply for VDD = 5V, 8Ω load, and AV = 1V/V, unless otherwise specified. Limits apply for TA = 25˚C. LM4898 Symbol Parameter Conditions IDD Quiescent Power Supply Current VIN = 0V, no load ISD Shutdown Current VSDMODE = VSHUTDOWN = GND Po Output Power THD = 1% (max); f = 1 kHz VIN = 0V, RL = 8 Ω LM4898LD, RL= 4Ω (Note 11) Typical Limit (Note 6) (Note 7) 3 6 5 10 0.1 1 1.4 Units (Limits) mA (max) µA (max) W (min) LM4898, RL= 8Ω 1 0.05 % f = 217Hz (Note 9) 83 dB (min) f = 1kHz (Note 9) 90 f = 217Hz (Note 10) 83 71 f = 1kHz (Note 10) 83 71 THD+N Total Harmonic Distortion+Noise Po = 0.4 Wrms; f = 1kHz PSRR Power Supply Rejection Ratio Vripple = 200mV sine p-p 0.9 CMRR Common_Mode Rejection Ratio f = 217Hz VCM = 200mVDD 50 dB VOS Output Offset VIN = 0V 2 mV VSDIH Shutdown Voltage Input High SD Mode = GND 0.9 V VSDIL Shutdown Voltage Input Low SD Mode = GND 0.7 V VSDIH Shutdown Voltage Input High SD Mode = VDD 0.9 V VSDIL Shutdown Voltage Input Low SD Mode = VDD 0.7 V www.national.com 4 LM4898 Symbol Parameter Conditions Typical Limit (Note 6) (Note 7) 2.5 5 .5 Units (Limits) IDD Quiescent Power Supply Current VIN = 0V, no load 4 9 ISD Shutdown Current VSDMODE = VSHUTDOWN = GND 0.1 1 Po Output Power THD = 1% (max); f = 1kHz LM4898, RL = 8Ω 0.35 W THD+N Total Harmonic Distortion+Noise Po = 0.25Wrms; f = 1kHz 0.03 % PSRR Power Supply Rejection Ratio Vripple = 200mV sine p-p f = 217Hz (Note 9) 83 dB f = 1kHz (Note 9) 84 VIN = 0V, RL = 8 Ω CMRR Common-Mode Rejection Ratio f = 217Hz (Note 10) 83 f = 1kHz (Note 10) 83 f = 217Hz VCM = 200mVPP mA (max) µA (max) 50 dB VOS Output Offset VIN = 0V 2 mV VSDIH Shutdown Voltage Input High SD Mode = GND 0.8 V VSDIL Shutdown Voltage Input Low SD Mode = GND 0.6 V VSDIH Shutdown Voltage Input High SD Mode = VDD 0.8 V VSDIL Shutdown Voltage Input Low SD Mode = VDD 0.6 V Note 1: All voltages are measured with respect to the ground 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 number given in Absolute Maximum Ratings, whichever is lower. 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: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis. Note 8: For micro SMD only, shutdown current is measured in a Normal Room Environment. Exposure to direct sunlight will increase ISD by a maximum of 2µA. Note 9: Unterminated input. Note 10: 10Ω terminated input. Note 11: When driving 4Ω loads from a 5V supply, the LM4898LD must be mounted to a circuit board with the exposed-DAP area soldered down to a 1sq. in plane of 1oz. copper.. External Components Description (Figure 1) Components Functional Description 1. 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. 2. 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. 3. Ri Inverting input resistance which sets the closed-loop gain in conjunction with Rf. 4. Rf Feedback resistance which sets the closed-loop gain in conjunction with Ri. 5 www.national.com LM4898 Electrical Characteristics VDD = 3V (Notes 1, 2, 8) The following specifications apply for VDD = 3V, 8Ω load and AV = 1V/V, unless otherwise specified. Limits apply for TA = 25˚C. LM4898 Typical Performance Characteristics LD Specific Characteristics THD+N vs Frequency VDD = 5V, RL = 4Ω, PO = 1W THD+N vs Output Power VDD = 5V, RL = 4Ω 200737A1 200737A3 LM4898LD Power Dissipation vs Output Power LM4898LD Power Derating Curve 200737A4 www.national.com 200737A5 6 LM4898 Typical Performance Characteristics Non-LD Specific Characteristics THD+N vs Frequency VDD = 3V, RL = 8Ω, PO = 275mW THD+N vs Frequency VDD = 5V, RL = 8Ω, PO = 400mW 200737A7 200737A9 THD+N vs Frequency VDD = 2.6V, RL = 8Ω, PO = 150mW THD+N vs Frequency VDD = 3V, RL = 4Ω, PO = 225mW 200737B3 200737B1 THD+N vs Output Power VDD = 5V, RL = 8Ω THD+N vs Frequency VDD = 2.6V, RL = 4Ω, PO = 150mW 200737B5 200737B7 7 www.national.com LM4898 Typical Performance Characteristics Non-LD Specific Characteristics (Continued) THD+N vs Output Power VDD = 3V, RL = 8Ω THD+N vs Output Power VDD = 3V, RL = 4Ω 200737B9 200737C1 THD+N vs Output Power VDD = 2.6V, RL = 4Ω THD+N vs Output Power VDD = 2.6V, RL = 8Ω 200737C3 200737C5 PSRR vs Frequency VDD = 3V, RL = 8Ω, Input 10Ω Terminated PSRR vs Frequency VDD = 5V, RL = 8Ω, Input 10Ω Terminated 200737C7 www.national.com 200737D0 8 LM4898 Typical Performance Characteristics Non-LD Specific Characteristics (Continued) Output Power vs Supply Voltage RL = 8Ω Output Power vs Supply Voltage RL = 4Ω 200737D3 200737D5 Power Dissipation vs Output Power Power Dissipation vs Output Power 200737D6 200737D6 Power Dissipation vs Output Power Output Power vs Load Resistance 200737D8 200737D9 9 www.national.com LM4898 Typical Performance Characteristics Non-LD Specific Characteristics (Continued) Supply Current vs Shutdown Voltage Shutdown Low Supply Current vs Shutdown Voltage Shutdown High 200737E0 200737E1 Clipping (Dropout) Voltage vs Supply Voltage Open Loop Frequency Response 200737E3 200737E2 Noise Floor Power Derating Curve 200737E4 200737E6 www.national.com 10 LM4898 Typical Performance Characteristics Non-LD Specific Characteristics (Continued) CMRR vs Frequency VDD = 5V, RL = 8Ω, 200mVpp CMRR vs Frequency VDD = 3V, RL = 8Ω, 200mVpp 200737E8 200737F0 PSRR vs Common Mode Voltage VDD = 3V, RL = 8Ω, 217Hz, 200mVpp PSRR vs Common Mode Voltage VDD = 5V 200737F2 200737F4 two input signals is amplified. In most applications, this would require input signals that are 180˚ out of phase with each other. The LM4898 can be used, however, as a single ended input amplifier while still retaining its fully differential benefits. In fact, completely unrelated signals may be placed on the input pins. The LM4898 simply amplifies the difference between them. All of these applications, either single-ended or fully differential, provide what is known as a "bridged mode" output (bridge-tied-load, BTL). This results in output signals at Vo1 and Vo2 that are 180˚ out of phase with respect to each other. Bridged mode operation is different from the singleended amplifier configuration that connects the load between the amplifier output and ground. A bridged amplifier design has distinct advantages over the single-ended configuration: it provides differential drive to the load, thus doubling maximum possible output swing for a specific supply voltage. Four times the output power is possible compared with a single-ended amplifier under the same conditions. This increase in attainable output power assumes that the Application Information DIFFERENTIAL AMPLIFIER EXPLANATION The LM4898 is a fully differential audio amplifier that features differential input and output stages. Internally this is accomplished by two circuits: a differential amplifier and a common mode feedback amplifier that adjusts the output voltages so that the average value remains VDD/2. When setting the differential gain, the amplifier can be considered to have two "halves". Each half uses an input and feedback resistor (Ri1 and Rf1) to set its respective closed-loop gain (see Figure 1). With Ri1 = Ri2 and Rf1 = Rf2, the gain is set at -Rf/Ri for each half. This results in a differential gain of (1) AVD = -Rf/Ri It is extremely important to match the input resistors to each other, as well as the feedback resistors to each other for best amplifier performance. See the Proper Selection of External Components section for more information. A differential amplifier works in a manner where the difference between the 11 www.national.com LM4898 Application Information PCB LAYOUT AND SUPPLY REGULATION CONSIDERATIONS FOR DRIVING 3Ω AND 4Ω LOADS Power dissipated by a load is a function of the voltage swing across the load and the load’s impedance. As load impedance decreases, load dissipation becomes increasingly dependent on the interconnect (PCB trace and wire) resistance between the amplifier output pins and the load’s connections. Residual trace resistance causes a voltage drop, which results in power dissipated in the trace and not in the load as desired. For example, 0.1Ω trace resistance reduces the output power dissipated by a 4Ω load from 1.4W to1.37W. This problem of decreased load dissipation is exacerbated as load impedance decreases. Therefore, to maintain the highest load dissipation and widest output voltage swing, PCB traces that connect the output pins to a load must be as wide as possible. (Continued) amplifier is not current limited or clipped. In order to choose an amplifier’s closed-loop gain without causing excess clipping, please refer to the Audio Power Amplifier Design section. A bridged configuration, such as the one used in theLM4898, 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 assumes that the input resistor pair and the feedback resistor pair are properly matched (see Proper Selection of External Components). BTL configuration eliminates the output coupling capacitor required in single supply, single-ended amplifier configurations. If an output coupling capacitor is not used in a single-ended output configuration, the half-supply bias across the load would result in both increased internal IC power dissipation as well as permanent loudspeaker damage. Further advantages of bridged mode operation specific to fully differential amplifiers like the LM4898 include increased power supply rejection ratio, common-mode noise reduction, and click and pop reduction. Poor power supply regulation adversely affects maximum output power. A poorly regulated supply’s output voltage decreases with increasing load current. Reduced supply voltage causes decreased headroom, output signal clipping, and reduced output power. Even with tightly regulated supplies, trace resistance creates the same effects as poor supply regulation. Therefore, making the power supply traces as wide as possible helps maintain full output voltage swing. EXPOSED-DAP PACKAGE PCB MOUNTING CONSIDERATIONS The LM4898’s exposed-DAP (die attach paddle) package (LD) provides a low thermal resistance between the die and the PCB to which the part is mounted and soldered. This allows rapid heat transfer from the die to the surrounding PCB copper traces, ground plane and, finally, surrounding air. The result is a low voltage audio power amplifier that produces 1.4W at ≤1% THD with a 4Ω load. This high power is achieved through careful consideration of necessary thermal design. Failing to optimize thermal design may compromise the LM4898’s high power performance and activate unwanted, though necessary, thermal shutdown protection. The LD package must have its DAP soldered to a copper pad on the PCB. The DAP’s PCB copper pad is connected to a large plane of continuous unbroken copper. This plane forms a thermal mass and heat sink and radiation area. Place the heat sink area on either outside plane in the case of a two-sided PCB, or on an inner layer of a board with more than two layers. Connect the DAP copper pad to the inner layer or backside copper heat sink area with 4 (2x2) vias. The via diameter should be 0.012in - 0.013in with a 0.050in pitch. Ensure efficient thermal conductivity by plating through and solder-filling the vias. Best thermal performance is achieved with the largest practical copper heat sink area. If the heatsink and amplifier share the same PCB layer, a nominal 2.5in2 (min) area is necessary for 5V operation with a 4Ω load. Heatsink areas not placed on the same PCB layer as the LM4898 should be 5in2 (min) for the same supply voltage and load resistance. The last two area recommendations apply for 25˚C ambient temperature. In all circumstances and conditions, the junction temperature must be held below 150˚C to prevent activating the LM4898’s thermal shutdown protection. The LM4898’s power derating curve in the Typical Performance Characteristics shows the maximum power dissipation versus temperature. Further detailed and specific information concerning PCB layout, fabrication, and mounting an LLP package is available from National Semiconductor’s package Engineering Group under application note AN-1187. www.national.com POWER DISSIPATION Power dissipation is a major concern when designing a successful amplifier, whether the amplifier is bridged or single-ended. Equation 2 states the maximum power dissipation point for a single-ended amplifier operating at a given supply voltage and driving a specified output load. (2) PDMAX=(VDD)2 /(2π2RL) Single-Ended However, a direct consequence of the increased power delivered to the load by a bridge amplifier is an increase in internal power dissipation versus a single-ended amplifier operating at the same conditions. (3) PDMAX = 4*(VDD)2/(2π2RL) Bridge Mode Since the LM4898 has bridged outputs, the maximum internal power dissipation is 4 times that of a single-ended amplifier. Even with this substantial increase in power dissipation, the LM4898 does not require additional heatsinking under most operating conditions and output loading. From Equation 3, assuming a 5V power supply and an 8. load,the maximum power dissipation point is 625mW. The maximum power dissipation point obtained from Equation 3 must not be greater than the power dissipation results from Equation4: (4) PDMAX = (TJMAX - TA)/θJA The LM4898’s θJA in an MUA10A package is 190˚C/W. Depending on the ambient temperature, TA, of the system surroundings, Equation 4 can be used to find the maximum internal power dissipation supported by the IC packaging. If the result of Equation 3 is greater than that of Equation 4, then either the supply voltage must be decreased, the load impedance increased, the ambient temperature reduced, or theθJA reduced with heatsinking. In many cases, larger traces near the output, VDD, and GND pins can be used to lower the θJA. The larger areas of copper provide a form of heatsinking allowing higher power dissipation. For the typical application of a 5V power supply, with an 8Ω load, the maximum ambient temperature possible without violating the maximum junction temperature is approximately 30˚C provided that device operation is around the maximum power dissipation point. Recall that internal power dissipation is a 12 PROPER SELECTION OF EXTERNAL COMPONENTS Proper selection of external components in applications using integrated power amplifiers is critical when optimizing device and system performance. Although the LM4898 is tolerant to a variety of external component combinations, consideration of component values must be made when maximizing overall system quality. The LM4898 is unity-gain stable, giving the designer maximum system flexibility. The LM4898 should be used in low closed-loop gain configurations to minimize THD+N values and maximize signal to noise ratio. Low gain configurations require large input signals to obtain a given output power. Input signals equal to or greater than 1Vrms are available from sources such as audio codecs. Please refer to the Audio Power Amplifier Design section for a more complete explanation of proper gain selection. When used in its typical application as a fully differential power amplifier the LM4898 does not require input coupling capacitors for input sources with DC common-mode voltages of less than VDD. Exact allowable input common-mode voltage levels are actually a function of VDD, Ri, and Rf and may be determined by Equation 5: (5) VCMi < (VDD-1.2)*((Rf+(Ri)/(Rf)-VDD*(Ri/2Rf) Rf/Ri=AVD (6) (Continued) function of output power. If typical operation is not around the maximum power dissipation point, the LM4898 can operate at higher ambient temperatures. Refer to the Typical Performance Characteristics curves for power dissipation information. POWER SUPPLY BYPASSING As with any power amplifier, proper supply bypassing is critical for low noise performance and high power supply rejection ratio (PSRR). The capacitor location on both the bypass and power supply pins should be as close to the device as possible. A larger half-supply bypass capacitor improves PSRR because it increases half-supply stability. Typical applications employ a 5V regulator with 10µF and0.1µF bypass capacitors that increase supply stability. This, however, does not eliminate the need for bypassing the supply nodes of the LM4898. Although the LM4898 will operate without the bypass capacitor CB, the PSRR may decrease. A 1µF capacitor is recommended for CB. This value maximizes PSRR performance. Lesser values may be used, but PSRR decreases at frequencies below 1kHz. The issue of CB selection is thus dependant upon desired PSRR and click and pop performance as explained in the section Proper Selection of External Components. Special care must be taken to match the values of the feedback resistors (Rf1 and Rf2) to each other as well as matching the input resistors (Ri1 and Ri2) to each other (see Figure 1). Because of the balanced nature of differential amplifiers, resistor matching differences can result in net DC currents across the load. This DC current can increase power consumption, internal IC power dissipation, reduce PSRR, and possibly damaging the loudspeaker. The chart below demonstrates this problem by showing the effects of differing values between the feedback resistors while assuming that the input resistors are perfectly matched. The results below apply to the application circuit shown in Figure 1, and assumes that VDD = 5V, RL = 8Ω, and the system has DC coupled inputs tied to ground. SHUTDOWN FUNCTION In order to reduce power consumption while not in use, the LM4898 contains shutdown circuitry that is used to turn off the amplifier’s bias circuitry. In addition, the LM4898 contains a Shutdown Mode pin, allowing the designer to designate whether the part will be driven into shutdown with a high level logic signal or a low level logic signal. This allows the designer maximum flexibility in device use, as the Shutdown Mode pin may simply be tied permanently to either VDD or GND to set the LM4898 as either a "shutdown-high" device or a "shutdown-low" device, respectively. The device may then be placed into shutdown mode by toggling the Shutdown Select pin to the same state as the Shutdown Mode pin. For simplicity’s sake, this is called "shutdown same", as the LM4898 enters shutdown mode whenever the two pins are in the same logic state. The trigger point for either shutdown high or shutdown low is shown as a typical value in the Supply Current vs. Shutdown 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 maybe greater than the typical value of 0.1µA. 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 (or pull-down, depending on shutdown high or low application). This scheme guarantees that the shutdown pin will not float, thus preventing unwanted state changes. Tolerance R f1 Rf2 Vo2-Vo1 ILOAD 20% 0.8R 1.2R -0.5V 62.5mA 10% 0.9R 1.1R -0.250V 31.25mA 5% 0.95R 1.05R -0.125V 15.63mA 1% 0.99R 1.01R -0.025V 3.125mA 0 R R R 0 Similar results would occur if the input resistors were not carefully matched. Adding input coupling capacitors in between the signal source and the input resistors will eliminate this problem, however, to achieve best performance with minimum component count it is highly recommended that both the feedback and input resistors matched to 1% tolerance or better. 13 www.national.com LM4898 Application Information LM4898 Application Information duce 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 8. (Continued) AUDIO POWER AMPLIFIER DESIGN Design a 1W/8Ω Audio Amplifier Given: 1W • Power Output 8Ω • Load Impedance 1Vrms • Input Level 20kΩ • Input Impedance 100Hz–20kHz ± 0.25dB • Bandwidth A designer must first determine the minimum supply rail to obtain the specified output power. The supply rail can easily be found by extrapolating from the Output Power vs. Supply Voltage graphs in the Typical Performance Characteristics section. A second way to determine the minimum supply rail is to calculate the required Vopeak using Equation 7 and add the dropout voltages. Using this method, the minimum supply voltage is (Vopeak +(VDO TOP+(VDO BOT )),where VDO BOT and VDO TOP are extrapolated from the Dropout Voltage vs. Supply Voltage curve in the Typical Performance Characteristics section. (8) Rf / Ri = AVD From Equation 8, the minimum AVD is 2.83. Since the desired input impedance was 20kΩ, a ratio of 2.83:1 of Rf to Ri results in an allocation of Ri = 20kΩ for both input resistors and Rf= 60kΩ for both feedback resistors. The final design step is to address the bandwidth requirement which must be stated as a single -3dB frequency point. Five times away from a -3dB point is 0.17dB down from passband response which is better than the required ± 0.25dB specified. fH = 20kHz * 5 =100kHz The high frequency pole is determined by the product of the desired frequency pole, fH , and the differential gain, AVD .With a AVD = 2.83 and fH = 100kHz, the resulting GBWP = 150kHz which is much smaller than the LM4898 GBWP of 10MHz. This figure displays that if a designer has a need to design an amplifier with a higher differential gain, the LM4898 can still be used without running into bandwidth limitations. (7) Using the Output Power vs. Supply Voltage graph for an 8Ω load, the minimum supply rail just about 5V. Extra supply voltage creates headroom that allows the LM4898 to repro- www.national.com 14 LM4898 Physical Dimensions inches (millimeters) unless otherwise noted LLP Order Number LM4898LD NSPackage Number LDA10B 15 www.national.com LM4898 Physical Dimensions inches (millimeters) unless otherwise noted (Continued) Mini Small Outline (MSOP) Order Number LM4898MM NSPackage Number MUB10A www.national.com 16 inches (millimeters) unless otherwise noted (Continued) 9-Bump micro SMD Order Number LM4898ITL, LM4898ITLX NS Package Number TLA09AAA X1 = 1.514 ± 0.03 X2 = 1.514 ± 0.03 X3 = 0.600 ± 0.075 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. National Semiconductor Americas Customer Support Center Email: [email protected] Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 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 Semiconductor Asia Pacific Customer Support Center Email: [email protected] National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: [email protected] Tel: 81-3-5639-7560 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. LM4898 1 Watt Fully Differential Audio Power Amplifier With Shutdown Select Physical Dimensions