LM4889 1 Watt Audio Power Amplifier General Description Key Specifications The LM4889 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 watt of continuous average power to an 8Ω BTL load with less than 2% 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 LM4889 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 LM4889 features a low-power consumption shutdown mode, which is achieved by driving the shutdown pin with a logic low. Additionally, the LM4889 features an internal thermal shutdown protection mechanism. The LM4889 contains advanced pop & click circuitry to eliminate noise which would otherwise occur during turn-on and turn-off transitions. The LM4889 is unity-gain stable and can be configured by external gain-setting resistors. j Improved PSRR at 217Hz, 5 - 3.3V 75dB j Power Output at 5.0V & 2% THD 1.0W(typ.) j Power Output at 3.3V & 1% THD 400mW(typ.) j Shutdown Current at 3.3 & 2.6V 0.01µA(typ.) Features n Available in space-saving MSOP, SOIC, LLP, and micro SMD packages n Ultra low current shutdown mode (3.3 to 2.6V - 0.01µA) n Can drive capacitive loads up to 500 pF n Improved pop & click circuitry eliminates noises during turn-on and turn-off transitions n 2.2 - 5.5V operation n No output coupling capacitors, snubber networks or bootstrap capacitors required n Unity-gain stable n External gain configuration capability Applications n Mobile Phones n PDAs n Portable electronic devices Typical Application 20035801 FIGURE 1. Typical Audio Amplifier Application Circuit Boomer ® is a registered trademark of National Semiconductor Corporation. © 2003 National Semiconductor Corporation DS200358 www.national.com LM4889 1 Watt Audio Power Amplifier June 2003 LM4889 Connection Diagrams Small Outline (SO) Package SO Marking 20035872 Top View Order Number LM4889MA See NS Package Number M08A Top View XY - Date Code TT - Die Traceability Bottom 2 lines - Part Number Mini Small Outline (MSOP) Package MSOP Marking 20035835 20035871 Top View G - Boomer Family A2 - LM4889MM 20035836 Top View Order Number LM4889MM See NS Package Number MUA08A 8 Bump micro SMD 8 Bump micro SMD Marking 20035879 Top View X - Date Code T - Die Traceability G - Boomer Family A3 - LM4889ITL 20035887 Top View Order Number LM4889ITL, LM4889ITLX See NS Package Number TLA08AAA LLP Package 10 Pin LLP Marking 20035831 Top View Z - Assembly Plant Date Code (M for Malacca) XY - 2 Digit Date Code TT - Die Traceability L4889 - LM4889LD 20035830 Top View Order Number LM4889LD See NS Package Number LDA10B www.national.com 2 θJA (8 Bump micro SMD) (Note 10) (Note 2) 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 −65˚C to +150˚C Power Dissipation (Note 3) Internally Limited ESD Susceptibility (Note 4) 2000V ESD Susceptibility (Note 5) 200V Junction Temperature θJC (MSOP) 56˚C/W θJA (MSOP) 190˚C/W θJA (LLP) 220˚C/W Soldering Information See AN-1112 "microSMD Wafers Level Chip Scale Package". −0.3V to VDD +0.3V Input Voltage 210˚C/W Operating Ratings 150˚C Temperature Range Thermal Resistance θJC (SOP) 35˚C/W θJA (SOP) 150˚C/W TMIN ≤ TA ≤ TMAX −40˚C ≤ TA ≤ 85˚C 2.2V ≤ VDD ≤ 5.5V Supply Voltage Electrical Characteristics VDD = 5V (Notes 1, 2) The following specifications apply for VDD = 5V, AV = 2, and 8Ω load unless otherwise specified. Limits apply for TA = 25˚C. LM4889 Symbol Parameter Conditions Units (Limits) Typical Limit (Note 6) (Notes 7, 9) VIN = 0V, Io = 0A, no Load 4 8 mA (max) VIN = 0V, Io = 0A, with BTL Load 5 8 mA (max) 0.1 1 µA (max) IDD Quiescent Power Supply Current ISD Shutdown Current VSDIH Shutdown Voltage Input High 1.2 V (min) VSDIL Shutdown Voltage Input Low 0.4 V (max) Po Output Power THD = 2% (max); f = 1 kHz THD+N Total Harmonic Distortion+Noise Power Supply Rejection Ratio PSRR Vshutdown = GND (Note 8) 1 W Po = 0.4 Wrms; f = 1kHz 0.1 % Vripple = 200mV sine p-p fripple = 217Hz fripple = 1kHz 62 66 dB dB Vripple = 200mV sine p-p Input Floating 75 68 dB Electrical Characteristics VDD = 3.3V (Notes 1, 2) The following specifications apply for VDD = 3.3V, AV = 2, and 8Ω load unless otherwise specified. Limits apply for TA = 25˚C. LM4889 Symbol Parameter Conditions Typical Limit (Note 6) (Notes 7, 9) Units (Limits) VIN = 0V, Io = 0A, no Load 3.5 7 mA (max) VIN = 0V, Io = 0A, with BTL Load 4.5 7 mA (max) Vshutdown = GND (Note 8) 0.01 1 µA (max) 1.2 V (min) 0.4 V (max) IDD Quiescent Power Supply Current ISD Shutdown Current VSDIH Shutdown Voltage Input High VSDIL Shutdown Voltage Input Low Po Output Power THD = 1% (max); f = 1kHz 0.4 W THD+N Total Harmonic Distortion+Noise Po = 0.25Wrms; f = 1kHz 0.1 % PSRR Power Supply Rejection Ratio Vripple = 200mV sine p-p fripple = 217Hz fripple =1kHz 60 62 dB dB 3 www.national.com LM4889 Absolute Maximum Ratings LM4889 Electrical Characteristics VDD = 2.6V (Notes 1, 2) The following specifications apply for VDD = 2.6V, AV = 2, and 8Ω load unless otherwise specified. Limits apply for TA = 25˚C. LM4889 Symbol IDD Parameter Quiescent Power Supply Current Conditions Typical Limit Units (Limits) (Note 6) (Notes 7, 9) VIN = 0V, Io = 0A, no Load 2.6 6 mA (max) VIN = 0V, Io = 0A, with BTL Load 3.0 6 mA (max) 1 µA (max) ISD Shutdown Current Vshutdown = GND (Note 8) 0.01 P0 Output Power ( 8Ω ) Output Power ( 4Ω ) THD = 1% (max); f = 1 kHz THD = 1% (max); f = 1 kHz 0.2 0.22 W W THD+N Total Harmonic Distortion+Noise Po = 0.1Wrms; f = 1kHz 0.08 % Power Supply Rejection Ratio Vripple = 200mV sine p-p fripple = 217Hz fripple = 1kHz 44 44 dB dB PSRR 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. For the LM4889, see power derating currents for additional information. Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Note 5: Machine Model, 220 pF–240 pF 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: 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: Datasheet min/max specification limits are guaranteed by design, test or statistical analysis. Note 10: All bumps have the same thermal resistance and contribute equally when used to lower thermal resistance. The LM4889ITL demo board (views featured in the Application Information section) has two inner layers, one for VDD and one for GND. The planes each measure 600mils x 600mils (15.24mm x 15.24mm) and aid in spreading heat due to power dissipation within the IC. 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/(2π 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/(2π 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. AVD = 2*(Rf/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. www.national.com 4 THD+N vs Frequency at VDD = 3.3V, 8Ω RL, and PWR = 150mW THD+N vs Frequency at VDD = 5V, 8Ω RL, and PWR = 250mW 20035837 20035838 THD+N vs Frequency at VDD = 2.6V, 4Ω RL, and PWR = 100mW THD+N vs Frequency at VDD = 2.6V, 8Ω RL, and PWR = 100mW 20035839 20035840 THD+N vs Power Out at VDD = 3.3V, 8Ω RL, 1kHz THD+N vs Power Out at VDD = 5V, 8Ω RL, 1kHz 20035875 20035842 5 www.national.com LM4889 Typical Performance Characteristics LM4889 Typical Performance Characteristics (Continued) THD+N vs Power Out at VDD = 2.6V, 8Ω RL, 1kHz THD+N vs Power Out at VDD = 2.6V, 4Ω RL, 1kHz 20035843 20035844 Power Supply Rejection Ratio (PSRR) at VDD = 5V Power Supply Rejection Ratio (PSRR) at VDD = 5V 20035845 20035873 Input terminated with 10Ω R Input Floating Power Supply Rejection Ratio (PSRR) at VDD = 2.6V Power Supply Rejection Ratio (PSRR) at VDD = 3.3V 20035847 20035846 Input terminated with 10Ω R www.national.com Input terminated with 10Ω R 6 LM4889 Typical Performance Characteristics (Continued) Power Dissipation vs Output Power VDD = 5V Power Dissipation vs Output Power VDD = 3.3V 20035849 20035848 Power Dissipation vs Output Power VDD = 2.6V Output Power vs Load Resistance 20035874 20035850 Supply Current vs Shutdown Voltage Clipping (Dropout) Voltage vs Supply Voltage 20035852 20035853 7 www.national.com LM4889 Typical Performance Characteristics (Continued) Open Loop Frequency Response Frequency Response vs Input Capacitor Size 20035855 20035854 Noise Floor Power Derating Curves (PDMAX = 670mW) 20035832 20035856 Power Derating Curves - 10 Pin LD pkg (PDMAX = 670mW) Power Derating Curves - 8 bump µSMD (PDMAX = 670mW) 20035833 www.national.com 20035834 8 BRIDGE CONFIGURATION EXPLANATION As shown in Figure 1, the LM4889 has two operational amplifiers internally, allowing for a few different amplifier configurations. 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 20kΩ 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) POWER SUPPLY BYPASSING As with any amplifier, proper supply bypassing is critical for low noise performance and high power supply rejection. The capacitor location on both the bypass and power supply pins should be as close to the device as possible. Typical applications employ a 5V regulator with 10 µF tantalum or electrolytic capacitor and a ceramic bypass capacitor which aid in supply stability. This does not eliminate the need for bypassing the supply nodes of the LM4889. 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. 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. SHUTDOWN FUNCTION In order to reduce power consumption while not in use, the LM4889 contains a shutdown pin to externally turn off the amplifier’s bias circuitry. This shutdown feature turns the amplifier off when a logic low is placed on the shutdown pin. By switching the shutdown pin to ground, the LM4889 supply current draw will be minimized in idle mode. While the device will be disabled with shutdown pin voltages less than 0.5VDC, the idle current may be greater than the typical value of 0.1µA. (Idle current is measured with the shutdown pin grounded). In many applications, a microcontroller or microprocessor output is used to control the shutdown circuitry to provide a quick, smooth transition into shutdown. Another solution is to use a single-pole, single-throw switch in conjunction with an external pull-up resistor. When the switch is closed, the shutdown pin is connected to ground and disables the amplifier. If the switch is open, then the external pull-up resistor will enable the LM4889. This scheme guarantees that the shutdown pin will not float thus preventing unwanted state changes. A bridge amplifier design has an advantage over the singleended 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 closed-loop gain without causing excessive clipping, please refer to the Audio Power Amplifier Design section. A bridge configuration, such as the one used in LM4889, also creates a second advantage over single-ended amplifiers. Since the differential outputs, Vo1 and Vo2, are biased at half-supply, no net DC voltage exists across the load. This eliminates the need for an output coupling capacitor which is required in a single supply, single-ended amplifier configuration. Without an output coupling capacitor, the half-supply bias across the load would result in both increased internal IC power dissipation and also possible loudspeaker damage. 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 LM4889 is tolerant of external component combinations, consideration to component values must be used to maximize overall system quality. The LM4889 is unity-gain stable which gives the designer maximum system flexibility. The LM4889 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 closedloop 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 reasons. 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 LM4889 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. (1) PDMAX = 4*(VDD)2/(2π2RL) It is critical that the maximum junction temperature TJMAX of 150˚C is not exceeded. TJMAX can be determined from the power derating curves by using PDMAX and the PC board foil area. By adding additional copper foil, the thermal resistance of the application can be reduced from a free air value of 150˚C/W, resulting in higher PDMAX. Additional copper foil can be added to any of the leads connected to the LM4889. It is especially effective when connected to VDD, GND, and the output pins. Refer to the application information on the LM4889 reference design board for an example of good heat sinking. If TJMAX still exceeds 150˚C, then additional changes must be made. These changes can include re9 www.national.com LM4889 duced 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. Application Information LM4889 Application Information supply voltage would be (Vopeak + (VODTOP + VODBOT)), where VODBOT and VODTOP are extrapolated from the Dropout Voltage vs Supply Voltage curve in the Typical Performance Characteristics section. (Continued) 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 100 Hz to 150 Hz. Thus, using a large input capacitor may not increase actual system performance. (2) 5V is a standard voltage in most applications, it is chosen for the supply rail. Extra supply voltage creates headroom that allows the LM4889 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. 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 LM4889 turns on. The slower the LM4889’s outputs ramp to their quiescent DC voltage (nominally 1/2 VDD), the smaller the turn-on pop. Choosing CB equal to 1.0 µF along with a small value of Ci (in the range of 0.1 µF to 0.39 µF), should produce a virtually clickless and popless shutdown function. While the device will function properly, (no oscillations or motorboating), with CB equal to 0.1 µF, the device will be much more susceptible to turn-on clicks and pops. Thus, a value of CB equal to 1.0 µF is recommended in all but the most cost sensitive designs. (3) Rf/Ri = AVD/2 From Equation 3, the minimum AVD is 2.83; use AVD = 3. Since the desired input impedance was 20 kΩ, and with a AVD impedance of 2, a ratio of 1.5:1 of Rf to Ri results in an allocation of Ri = 20 kΩ and Rf = 30 kΩ. 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. AUDIO POWER AMPLIFIER DESIGN fL = 100 Hz/5 = 20 Hz A 1W/8Ω AUDIO AMPLIFIER fH = 20 kHz * 5 = 100 kHz Given: Power Output Load Impedance Input Level Input Impedance Bandwidth As stated in the External Components section, Ri in conjunction with Ci create a highpass filter. 1 Wrms 8Ω 1 Vrms Ci ≥ 1/(2π*20 kΩ*20 Hz) = 0.397 µF; use 0.39 µF 20 kΩ 100 Hz–20 kHz ± 0.25 dB 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 = 100 kHz, the resulting GBWP = 300kHz which is much smaller than the LM4889 GBWP of 2.5MHz. This calculation shows that if a designer has a need to design an amplifier with a higher differential gain, the LM4889 can still be used without running into bandwidth limitations. 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. A second way to determine the minimum supply rail is to calculate the required Vopeak using Equation 2 and add the output voltage. Using this method, the minimum www.national.com 10 LM4889 Application Information (Continued) 20035824 FIGURE 2. Higher Gain Audio Amplifier The LM4889 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 2 to bandwidth limit the amplifier. This feedback capacitor creates a low pass filter that elimi- nates 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 = 20kΩ and C4 = 25pf. These components result in a -3dB point of approximately 320kHz. 11 www.national.com LM4889 Application Information (Continued) 20035829 FIGURE 3. Differential Amplifier Configuration for LM4889 www.national.com 12 LM4889 Application Information (Continued) 20035880 FIGURE 4. Reference Design Board and Layout - micro SMD 13 www.national.com LM4889 Application Information LM4889 micro SMD DEMO BOARD ARTWORK (Continued) Composite View Silk Screen 20035886 20035881 Top Layer Bottom Layer 20035882 20035883 Inner Layer Ground Inner Layer VDD 20035885 www.national.com 20035884 14 LM4889 Application Information (Continued) REFERENCE DESIGN BOARD and PCB LAYOUT GUIDELINES - MSOP & SO Boards 20035868 FIGURE 5. Reference Design Board 15 www.national.com LM4889 Application Information (Continued) LM4889 MSOP DEMO BOARD ARTWORK LM4889 SO DEMO BOARD ARTWORK Silk Screen Silk Screen 20035877 20035876 Top Layer Top Layer 20035866 20035863 Bottom Layer Bottom Layer 20035867 20035864 www.national.com 16 LM4889 Physical Dimensions inches (millimeters) unless otherwise noted 8-Bump micro SMD Order Number LM4889ITL, LM4889ITLX NS Package Number TLA08AAA X1 = 1.514 ± 0.03 X2 = 1.514 ± 0.03 X3 = 0.600 ± 0.075 MSOP Order Number LM4889MM NS Package Number MUA08A 17 www.national.com LM4889 Physical Dimensions inches (millimeters) unless otherwise noted (Continued) LLP Order Number LM4889LD NS Package Number LDA10B www.national.com 18 LM4889 1 Watt Audio Power Amplifier Physical Dimensions inches (millimeters) unless otherwise noted (Continued) SO Order Number LM4889MA NS Package Number M08A 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.