LM4663 2 Watt Stereo Class D Audio Power Amplifier with Stereo Headphone Amplifier General Description The LM4663 is a fully integrated single supply, high efficiency Class D audio power amplifier solution. The LM4663 utilizes a continuous time delta-sigma modulation technique that lowers output noise and THD when compared to conventional pulse width modulators. The LM4663 also features a stereo headphone amplifier that delivers 80mW into a 32Ω headset with less than 0.5% THD. The LM4663 has two stereo inputs that can be selected to drive either the headphone amplifier or the Class D amplifier. All amplifiers are protected with thermal shutdown. In standby mode, the LM4663 draws an extremely low 2µA supply current. With a 4Ω load, the IC’s efficiency for a 250mW power level is 69%, reaching 83% at a power level of 2W. The IC features click and pop reduction circuitry that minimizes audible popping during device turn-on and turn-off. The LM4663 is available in a 24-lead TSSOP package, ideal for portable and desktop computer applications. Key Specifications n PO at THD+N = 1% n THD+N at 1kHz at 1 Watt into 4Ω (Power Amp) n n n n n n Efficiency at 2 Watt into 4Ω Efficiency at 250mW into 4Ω Total quiescent power supply current Total shutdown power supply current THD+N 1kHz, 20mW, 32Ω (Headphone) Single supply range 83% (typ) 69% (typ) 22mA (typ) 2µA (typ) 0.15% (typ) 4.5V to 5.5V Features n n n n n n Delta-sigma modulator. Two stereo input selector. “Click and pop” suppression circuitry. Micropower shutdown mode. 24 lead TSSOP package (No heatsink required). Stereo headphone amplifier. Applications n Portable computers n Desktop computers n Multimedia Monitors 2.1W (typ) 0.2% (typ) Block Diagram Connection Diagram TSSOP Package DS101269-2 DS101269-1 Top View Order Number LM4663MT See NS Package Number MTC24 (TSSOP Package) BOOMER™ is a trademark of National Semiconductor Corporation. © 2000 National Semiconductor Corporation DS101269 www.national.com LM4663 2 Watt Stereo Class D Audio Power Amplifier with Stereo Headphone Amplifier January 2000 LM4663 Absolute Maximum Ratings (Note 2) Soldering Information TSSOP Package Vapor Phase (60 sec.) 215˚C Infrared (15 sec.) 220˚C See AN-450 “Surface Mounting and their Effects on Product Reliability” for other methods of soldering surface mount devices. If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Input Voltage Power Dissipation (Note 3) Load Resistance ESD Susceptibility(Note 4) Pins 5,7,18,20 ESD Susceptibility (Note 5) Pins 5,7,18,20 Junction Temperature (Note 6) Storage Temperature 6.0V −0.3V to VDD +0.3V Internally Limited 2.5Ω, min 2000V 600V 200V 50V 150˚C −65˚C ≤ TA ≤ 150˚C Operating Ratings(Notes 1, 2) Temperature Range TMIN ≤ TA ≤ TMAX −40˚C ≤ TA ≤ +85˚C Supply Voltage 4.5V ≤ VDD ≤ 5.5V Thermal Resistance (TSSOP Package) 80˚C/W θJA 20˚C/W θJC Electrical Characteristics (Notes 1, 2, 7) The following specifications apply for VDD = 5V, RL = 4Ω, LC filter values as shown in Figure 1, unless otherwise specified. Limits apply for TA = 25˚C. Symbol Parameter Conditions LM4663 Typical Max Min 5 5.5 4.5 Units VS Operating Supply Voltage Range IS Quiescent Power Supply Current, Class D Mode VIN = 0VRMS, VHPSEL = 0V 22 35 mA IS Quiescent Power Supply Current, Headphone Mode VIN = 0VRMS, VHPSEL = VS 5 10 mA ISD Quiescent Power Supply Current, Shutdown Mode VSD = 5V 2 µA RIN Input Resistance in Both Modes 20 kΩ VIH Minimum High Level Input Voltage Shutdown Pin & Input Select Pin VIL Maximum Low Level Input Voltage Shutdown Pin & Input Select Pin VIH Minimum High Level Input Voltage Headphone Select Pin VIL Maximum Low Level Input Voltage Headphone Select Pin 4.5 0.5 V V V 4.5 0.5 V V Power Amplifiers POR Output Power, Per Channel PD1 Power Dissipation PD2 Power Dissipation PD3 Power Dissipation EFF1 Efficiency THD+N ≤ 1%, fIN = 1kHz PO = 2W/Chan, fIN = 1kHz PO = 1W/Chan, fIN = 1kHz PO = .25W/Chan, fIN = 1kHz PO = 2W/Chan, fIN = 1kHz EFF2 Efficiency EFF3 Efficiency THD+N Harmonic Distortion + Noise PO = 1W/Chan, RL = 8Ω, fIN = 1kHz PO = .25W/Chan, fIN = 1kHz PO = 1W/Chan, fIN = 1kHz VNOISE PSRR 2.1 W 0.82 W 0.49 W 0.23 W 83 % 85 80 % 69 % 0.2 % Output Noise Voltage, RMS. A−Weighted RSOURCE = 50Ω, CIN = 1µF, BW = 8Hz to 22kHz 200 µV Power Supply Rejection Ratio (Referred to Input) 200mV, 1kHz, VIN = 0 44 1kHz, VIN = 100mV, RL = 4Ω 1kHz, VIN = 100mV, RL = 4Ω 13 dB 0.1 dB AV Voltage Gain AVL−AVR Stereo Gain Tracking www.national.com 2 dB (Continued) The following specifications apply for VDD = 5V, RL = 4Ω, LC filter values as shown in Figure 1, unless otherwise specified. Limits apply for TA = 25˚C. Symbol Parameter LM4663 Conditions Typical Max Units Min Headphone Amplifiers AV Voltage Gain THD+N ≤ 1%, RL = 32Ω, fIN = 1kHz PO = 20mW, RL = 32Ω, fIN = 1kHz RIN = 50Ω, CIN = 1µF, BW = 8Hz to 22kHz 200mV, 1kHz, VIN = 0, RL = 32Ω 1kHz, VIN = 100mV, RL = 32Ω AVL−AVR Stereo Gain Tracking 1kHz, VIN = 100mV, RL = 32Ω PO Power Out Per Channel THD+N Distortion + Noise VNOISE Output Noise Voltage, RMS PSRR Power Supply Rejection Ratio (Referred to Input) 80 mW 60 0.15 % 30 µV 44 dB 5.5 dB 0.1 dB 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: For operating at case temperatures above 25˚C, the device must be derated based on a 150˚C maximum junction temperature and a thermal resistance of θJA = 80˚C/W (junction to ambient). Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Note 5: Machine Model 220pF−240pF discharged through all pins. Note 6: The operating junction temperature maximum is 150˚C. Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Typical Performace Characteristics Efficiency vs Output Power Power Dissipation vs Output Power DS101269-10 DS101269-11 3 www.national.com LM4663 Electrical Characteristics (Notes 1, 2, 7) LM4663 Typical Performace Characteristics (Continued) Class D Amplifier In-Band Output Spectrum Class D Amplifier In-Band Output Spectrum DS101269-12 DS101269-13 Class D Amplifier THD + N vs Power vs Frequency Class D Amplifier THD + N vs Frequency vs Power DS101269-15 DS101269-14 Headphone THD + N vs Frequency vs Power DS101269-16 www.national.com 4 LM4663 Applications Information DS101269-3 FIGURE 1. Operating on a single 5V supply, this recommended application circuit is a complete solution with 2W Class D amplifiers that drive 4Ω speakers and 80mW amplifiers drive 32Ω headphones. Suggested Application Circuit The LM4663 achieves its specified performance using the recommended application circuit shown in Figure 1. The circuit provides full access to the stereo 2W/channel power amplifiers and the 80mW/channel stereo headphone amplifier. The HPSELECT (headphone select ) input is controlled by a stereo mini-plug/jack with additional control contact. Other applications of this device may use external generated logic signals to control this function. Control Pins The LM4663 has three control pins: INSEL, SD, and HPSEL. The INSEL pin is used to select between the two stereo inputs, VIN1 and VIN2. Connecting the INSEL pin to the positive supply selects VIN1, whereas pulling it to ground selects VIN2. Micropower shutdown operation is selected by pulling the SD to the positive supply. Applying the positive supply to the HPSEL pin selects the headphone amplifiers and grounding the HPSEL pin selects the Class D amplifiers. Table 1 is a summary of the function selected when applying ground or VDD to the control pins. TABLE 1. Function selected when applying VDD or GND to the INSEL, SD, and HPSEL control pins. Control Function Pin Apply GND INSEL 10 VIN1 L & R VIN2 L & R SD 9 Full power operation Micropower shutdown HPSEL 16 Deactivate headphone amps and activate Class D amps Deactivate Class D amps and activate headphone amps Apply VDD Output Filters The LM4663’s 2W power amplifiers use a Class D switching topology that requires a filter between the amplifier outputs and the load. The balanced, L-C filters shown in Figure 1 use component values recommended for a maximally flat magnitude in the pass-band and a cut-off frequency of 18kHz with a load impedance of 4Ω. We do not recommend omitting the filter because considerable out-of-band energy is present in the Class D output waveform. This energy would be dissipated in the load impedance’s resistive component, which diminishes efficiency. 5 www.national.com LM4663 Applications Information the power amp outputs and their associated pins. Short connections reduce inductance and EMI radiation from the output switching currents. Also, the distance from the switching outputs to the filter inductors is similarly minimized to reduce radiated noise. Table 4 is the recommended circuit’s bill-of-materials (BOM). Figure 8 is a photograph of the recommended four-layer PC board. (Continued) Bypass Pin Capacitor In order to achieve the largest unclipped output voltage swing, a DC reference voltage for the circuit is derived internally by a resistor divider from the power supply voltage. To reduce sensitivity to audio frequency variations on the reference voltage, a de-coupling capacitor is recommended between the BYPASS pin and the best available AC ground reference. This is typically the shield connection from the signal source. A poor choice is the power ground because considerable current flows from the LM4663 through pins 4,8,17, and 21 to the power supply return. This current is rich in harmonic frequencies related to the input audio frequency. These harmonics can easily couple into the signal path by sharing power ground conductors with the bypass capacitor connection. The result is increased THD. Minimum Load Resistance As specified in the Absolute Maximum Ratings, the minimum load resistance supported by the LM4663 at the output of the filters is 2.5 Ohms. Loads (usually loudspeakers) should be tested over the audio band to determine whether or not there are resonant points of diminshed impedance less than this limit. Output Filter Components Table 2 shows suggested standard values of the capacitor (C) and the inductor (L) used in Figure 1’s output filter for 4Ω and 8Ω loads. The bandwidth for each case is typically 18kHz. The board is designed for use with an external 5V supply, 4Ω speakers, and 32Ω headphones. Apply the supply voltage to the VDD pad and ground to the GND pad. Connect the left channel speaker between the Lout+ and Lout− pads and the right channel speaker between the Rout+ and Rout− pads. Connect the left and right headphone speakers to the HPL and HPR pads, respectively. The board has two sets of HPL and HPR pads. Use the set found across the top edge for a headphone jack like that shown in Figure 1. The other set found along the right edge can be used for a three terminal headphone jack. Ensure that a speaker’s + terminal is connected to an amplifier’s + output. This preserves the phase relationship between the left and right channels. The board accepts two stereo inputs. Apply channel 1’s right and left input signals to the Rin1 and Lin1 pads, respectively. Apply channel 2’s right and left input signals to the Rin2 and Lin2 pads, respectively. The board’s bottom edge has seven jumpers. From left to right, these jumpers select micropower shutdown, input channel, headphone amplifier, Class D amplifier, and headphone amplifier when plugging in headphones. Table 3 is a guide for selecting the various functions. TABLE 3. These are the functions selected by the jumpers on the recommended PC board. TABLE 2. Output filter component values for different load resistance. Load Resistance (Ω) Capacitor C (µF) Inductor L (µH) 4 2 22 8 1 44 Short Circuit Tolerance The LM4663, when used in the recommended application circuit, is tolerant of limited duration short circuit connections between the filtered positive and negative outputs. Shorts from either output to ground or supply voltage, or from the unfiltered outputs to any other low impedance node can result in permanent damage to the IC. Start-up Current The LM4663 exhibits abnormally high quiescent current drain when the supply voltage is below the specified operating range of 4.5 to 5.5V. It is, therefore, recommended that the IC be initially powered up in the shutdown mode (SD = VDD). Normal application of power from laboratory bench supplies is not usually a problem unless the current limit of the supply is set too low ( < 1A); however, some applications have a much lower current capability (such as USB applications). In these cases power must be applied with shutdown asserted and switched to the operating mode after power is present and settled. An external circuit that provides this condition automatically is given in Figure 2, and is recommended for those current-critical applications. Printed Circuit Board Layout Figures 3 through 7 show the layout of a recommended four-layer PC board that is optimized for the LM4663 and associated external components. This layout emphasizes short connections between the power reservoir capacitors near www.national.com 6 Jumper Function SD-L Shorting selects normal operation. SD-H Jumper is open. SD-H Shorting activates shutdown: micropower operation. SD-L Jumper is open. INSEL-L Shorting selects stereo input 1. INSEL-H Jumper is open. INSEL-H Shorting selects stereo input 2. INSEL-L Jumper is open. Class AB Shorting activates the headphone amplifier and deactivates the Class D amplifier. Class D and HP jack jumpers are open Class D Shorting activates the Class D amplifier and deactivates the headphone amplifier. Class AB and HP jack jumpers are open HP Jack Shorting allows the act of plugging in headphones to activate the headphone amplifier and deactivate the Class D amplifier. Removing headphones restores Class D amplifier operation and deactivates the headphone amplifier. Class AB and Class D jumpers are open. (Requires the use of a headphone jack like that shown in Figure 1.) LM4663 Applications Information (Continued) DS101269-4 FIGURE 2. At power-up, the LP3740 forces the LM4663 into shutdown, which prevents abnormal quiescent current flow through the amplifier. Once VCC rises above 4V and after a 200ms delay set by C1, normal amplifier operation is restored. DS101269-7 DS101269-5 FIGURE 5. Recommended PC board layout: Inner Layer ground plane layout FIGURE 3. Recommended PC board layout: Component side silkscreen DS101269-6 DS101269-8 FIGURE 4. Recommended PC board layout: Component side layout FIGURE 6. Recommended PC board layout: Inner Layer supply plane layout 7 www.national.com LM4663 Applications Information (Continued) DS101269-9 FIGURE 7. Recommended PC board layout: Bottom side layout TABLE 4. Suggested PC Board Bill-of-Materials for recommended PC boards. (See Figures 1 and 3 through 7) Component Footprint Type Value C1-C4 0805 SMD/Top 1µF C5-C7 7243 SMD/Top 220µF C8,C10,C12,C14 0805 SMD/Top .47µF C9,C11,C13,C15 3216 SMD/Top 2.2µF C16-C18 0805 SMD/Top 1µF C19-C22 0805 SMD/Bot 1µF R5a,R6a 0805 SMD 100k R7a 0805 SMD 1k L1-L4 D03316P−223 SMD 22µH U1 LM4663MT TSSOP www.national.com Size Comment ’D’ Tan./10V ’A’ Tan. No Silkscreen Coilcraft: (847)639−6400 http://www.coilcraft.com 24 Pin 8 National 2W Class D amplifier LM4663 Applications Information (Continued) DS101269-35 FIGURE 8. Recommended LM4663 PC Board 9 www.national.com LM4663 2 Watt Stereo Class D Audio Power Amplifier with Stereo Headphone Amplifier Physical Dimensions inches (millimeters) unless otherwise noted Order Number LM4663MT NS Package Number MTC24 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 Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: [email protected] www.national.com National Semiconductor Europe Fax: +49 (0) 1 80-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Français Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80 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 Response Group Tel: 65-2544466 Fax: 65-2504466 Email: [email protected] National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 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.