LM4674A LM4674A Filterless 2.5W Stereo Class D Audio Power Amplifier Literature Number: SNAS366 LM4674A Filterless 2.5W Stereo Class D Audio Power Amplifier General Description Key Specifications The LM4674A is a single supply, high efficiency, 2.5W/ channel, filterless switching audio amplifier. A low noise PWM architecture eliminates the output filter, reducing external component count, board area consumption, system cost, and simplifying design. The LM4674A is designed to meet the demands of mobile phones and other portable communication devices. Operating from a single 5V supply, the device is capable of delivering 2.5W/channel of continuous output power to a 4 load with less than 10% THD+N. Flexible power supply requirements allow operation from 2.4V to 5.5V. j Efficiency at 3.6V, 100mW into 8 80% (typ) j Efficiency at 3.6V, 500mW into 8 85% (typ) j Efficiency at 5V, 1W into 8 85% (typ) The LM4674A features high efficiency compared to conventional Class AB amplifiers. When driving an 8 speaker from a 3.6V supply, the device features 85% efficiency at PO = 500mW. Four gain options are pin selectable through the GAIN0 and GAIN1 pins. Output short circuit protection prevents the device from being damaged during fault conditions. Superior click and pop suppression eliminates audible transients on power-up/down and during shutdown. Independent left/right shutdown controls maximizes power savings in mixed mono/stereo applications. j Shutdown current j Quiescent Power Supply Current at 3.6V supply j Power Output at VDD = 5V, RL = 4, THD 10% j Power Output at VDD = 5V, RL = 8, THD 10% 4mA 2.5W (typ) 1.5W (typ) 0.1A (typ) Features n n n n n n n n n Output Short Circuit Protection Stereo Class D operation No output filter required Logic selectable gain Independent shutdown control Minimum external components Click and Pop suppression Micro-power shutdown Available in space-saving 2mm x 2mm x 0.6mm micro SMD package Applications n Mobile phones n PDAs n Laptops Boomer (R) is a registered trademark of National Semiconductor Corporation. (c) 2006 National Semiconductor Corporation DS201961 www.national.com LM4674A Filterless 2.5W Stereo Class D Audio Power Amplifier September 2006 LM4674A Typical Application 20196103 FIGURE 1. Typical Audio Amplifier Application Circuit www.national.com 2 LM4674A Connection Diagrams TL Package (2mmx2mmx0.6mm) 20196101 Top View Order Number LM4674ATL See NS Package Number TL1611A LM4674ATL Markings 20196125 Top View XY = 2 digit datecode TT = Die traceability G = Boomer Family I2 = LM4674ATL 3 www.national.com LM4674A Absolute Maximum Ratings (Notes 1, 2) Junction Temperature (TJMAX) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Thermal Resistance Supply Voltage (Note 1) Operating Ratings (Note 1) (Note 2) JA 6.0V Storage Temperature -65C to +150C Power Dissipation (Note 3) ESD Susceptibility, all other pins (Note 4) ESD Susceptibility (Note 5) 45.7C/W Temperature Range -0.3V to VDD +0.3V Input Voltage 150C TMIN TA TMAX Internally Limited -40C TA 85C 2.4V VDD 5.5V Supply Voltage 2000V 200V Electrical Characteristics VDD = 3.6V (Notes 1, 2) The following specifications apply for AV = 6dB, RL = 15H + 8 + 15H, f = 1kHz unless otherwise specified. Limits apply for TA = 25C. LM4674A Symbol VOS IDD Parameter Differential Output Offset Voltage Quiescent Power Supply Current ISD Shutdown Current VSDIH Shutdown Voltage Input High VSDIL Shutdown Voltage Input Low TWU Wake Up Time AV RIN Gain Input Resistance www.national.com Conditions Typical Limit (Note 6) (Note 7) Units (Limits) VIN = 0, VDD = 2.4V to 5.0V 5 VIN = 0, RL = , Both channels active, VDD = 3.6V 4 6 mA VIN = 0, RL = , Both channels active, VDD = 5V 5 7.5 mA VSD1 = VSD2 = GND VSHUTDOWN = 0.4V 0.03 mV 1 A 1.4 V (min) 0.4 V (max) 4.2 ms GAIN0, GAIN1 = GND 6 6 0.5 dB GAIN0 = VDD, GAIN1 = GND 12 12 0.5 dB GAIN0 = GND, GAIN1 = VDD 18 18 0.5 dB GAIN0, GAIN1 = VDD 24 24 0.5 AV = 6dB 28 k AV = 12dB 18.75 k AV = 18dB 11.25 k AV = 24dB 6.25 k 4 dB LM4674A Symbol Parameter Conditions Typical Limit (Note 6) (Note 7) Units (Limits) RL = 15H + 4 + 15H, THD = 10% f = 1kHz, 22kHz BW VDD = 5V 2.5 W VDD = 3.6V 1.2 W VDD = 2.5V 0.530 W 1.5 W RL = 15H + 8 + 15H, THD = 10% f = 1kHz, 22kHz BW VDD = 5V PO Output Power VDD = 3.6V 0.78 VDD = 2.5V 0.350 W 1.9 W VDD = 3.6V 1 W VDD = 2.5V 0.430 W 0.6 W RL = 15H + 4 + 15H, THD = 1% f = 1kHz, 22kHz BW VDD = 5V RL = 15H + 8 + 15H, THD = 1% f = 1kHz, 22kHz BW THD+N PSRR Total Harmonic Distortion Power Supply Rejection Ratio VDD = 5V 1.25 W VDD = 3.6V 0.63 W VDD = 2.5V 0.285 W PO = 500mW, f = 1kHz, RL = 8 0.07 % PO = 300mW, f = 1kHz, RL = 8 0.05 % VRIPPLE = 200mVP-P Sine, fRipple = 217Hz, Inputs AC GND, CI = 1F, input referred 75 dB VRIPPLE = 1VP-P Sine, fRipple = 1kHz, Inputs AC GND, CI = 1F, input referred 75 dB CMRR Common Mode Rejection Ratio VRIPPLE = 1VP-P fRIPPLE = 217Hz 67 dB Efficiency PO = 1W, f = 1kHz, RL = 8, VDD = 5V 85 % Crosstalk PO = 500mW, f = 1kHz 84 dB SNR Signal to Noise Ratio VDD = 5V, PO = 1W 96 dB eOS Output Noise Input referred, A-Weighted Filter 20 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, JA, and the ambient temperature, TA. The maximum allowable power dissipation is PDMAX = (TJMAX - TA)/ JA or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4674A see power derating currents for more information. Note 4: Human body model, 100pF discharged through a 1.5k resistor. Note 5: Machine Model, 220pF-240pF discharged through all pins. Note 6: Typicals are measured at 25C and represent the parametric norm. Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level). 5 www.national.com LM4674A Electrical Characteristics VDD = 3.6V (Notes 1, 2) The following specifications apply for AV = 6dB, RL = 15H + 8 + 15H, f = 1kHz unless otherwise specified. Limits apply for TA = 25C. (Continued) LM4674A 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. CI Input AC coupling capacitor which blocks the DC voltage at the amplifier's input terminals. www.national.com 6 LM4674A Block Diagrams 20196137 7 www.national.com LM4674A Block Diagrams (Continued) 20196138 Differential Input Configuration www.national.com 8 LM4674A Typical Performance Characteristics THD+N vs Output Power f = 1kHz, AV = 6dB, RL = 8 THD+N vs Output Power f = 1kHz, AV = 24dB, RL = 8 20196139 20196140 THD+N vs Output Power f = 1kHz, AV = 6dB, RL = 4 THD+N vs Output Power f= 1kHz, AV = 24dB, RL = 4 20196141 20196142 THD+N vs Frequency VDD = 3.6V, POUT = 250mW, RL = 8 THD+N vs Frequency VDD = 2.5V, POUT = 100mW, RL = 8 20196143 20196144 9 www.national.com LM4674A Typical Performance Characteristics (Continued) THD+N vs Frequency VDD = 5V, POUT = 375mW, RL = 8 THD+N vs Frequency VDD = 2. 5V, POUT = 100mW, RL = 4 20196145 20196146 THD+N vs Frequency VDD = 5V, POUT = 375mW, RL = 4 THD+N vs Frequency VDD = 3.6V, POUT = 250mW, RL = 4 20196147 20196148 Efficiency vs. Output Power RL = 8, f = 1kHz Efficiency vs. Output Power RL = 4, f = 1kHz 20196149 www.national.com 20196150 10 (Continued) Power Dissipation vs. Output Power RL = 4, f = 1kHz Power Dissipation vs. Output Power RL = 8, f = 1kHz 20196151 20196152 Output Power vs. Supply Voltage RL = 8, f = 1kHz Output Power vs. Supply Voltage RL = 4, f = 1kHz 20196153 20196154 Crosstalk vs. Frequency VDD = 3.6V, VRIPPLE = 1VP-P, RL = 8 PSRR vs. Frequency VDD = 3.6V, VRIPPLE= 200mVP-P, RL = 8 20196122 20196155 11 www.national.com LM4674A Typical Performance Characteristics LM4674A Typical Performance Characteristics (Continued) CMRR vs. Frequency VDD = 3.6V, VCM = 1VP-P, RL = 8 Supply Current vs. Supply Voltage No Load 20196157 www.national.com 20196158 12 unwanted state changes when /SD_ is floating. To minimize shutdown current, /SD_ should be driven to GND or left floating. If /SD_ is not driven to GND or floating, an increase in shutdown supply current will be noticed. GENERAL AMPLIFIER FUNCTION The LM4674A stereo Class D audio power amplifier features a filterless modulation scheme that reduces external component count, conserving board space and reducing system cost. The outputs of the device transition from VDD to GND with a 300kHz switching frequency. With no signal applied, the outputs (OUT_A and OUT_B) switch with a 50% duty cycle, in phase, causing the two outputs to cancel. This cancellation results in no net voltage across the speaker, thus there is no current to the load in the idle state. SINGLE-ENDED AUDIO AMPLIFIER CONFIGURATION The LM4674A is compatible with single-ended sources. When configured for single-ended inputs, input capacitors must be used to block and DC component at the input of the device. Figure 3 shows the typical single-ended applications circuit. With the input signal applied, the duty cycle (pulse width) of the LM4674A outputs changes. For increasing output voltage, the duty cycle of OUT_A increases, while the duty cycle of OUT_B decreases. For decreasing output voltages, the converse occurs. The difference between the two pulse widths yields the differential output voltage. AUDIO AMPLIFIER POWER SUPPLY BYPASSING/FILTERING Proper power supply bypassing is critical for low noise performance and high PSRR. Place the supply bypass capacitor as close to the device as possible. Typical applications employ a voltage regulator with 10F and 0.1F bypass capacitors that increase supply stability. These capacitors do not eliminate the need for bypassing of the LM4674A supply pins. A 1F capacitor is recommended. DIFFERENTIAL AMPLIFIER EXPLANATION As logic supplies continue to shrink, system designers are increasingly turning to differential analog signal handling to preserve signal to noise ratios with restricted voltage signs. The LM4674A features two fully differential amplifiers. A differential amplifier amplifies the difference between the two input signals. Traditional audio power amplifiers have typically offered only single-ended inputs resulting in a 6dB reduction of SNR relative to differential inputs. The LM4674A also offers the possibility of DC input coupling which eliminates the input coupling capacitors. A major benefit of the fully differential amplifier is the improved common mode rejection ratio (CMRR) over single ended input amplifiers. The increased CMRR of the differential amplifier reduces sensitivity to ground offset related noise injection, especially important in noisy systems. AUDIO AMPLIFIER INPUT CAPACITOR SELECTION Input capacitors may be required for some applications, or when the audio source is single-ended. Input capacitors block the DC component of the audio signal, eliminating any conflict between the DC component of the audio source and the bias voltage of the LM4674A. The input capacitors create a high-pass filter with the input resistors RI. The -3dB point of the high pass filter is found using Equation 1 below. (1) f = 1 / 2RINCIN The values for RI can be found in the EC table for each gain setting. The input capacitors can also be used to remove low frequency content from the audio signal. Small speakers cannot reproduce, and may even be damaged by low frequencies. High pass filtering the audio signal helps protect the speakers. When the LM4674A is using a single-ended source, power supply noise on the ground is seen as an input signal. Setting the high-pass filter point above the power supply noise frequencies, 217Hz in a GSM phone, for example, filters out the noise such that it is not amplified and heard on the output. Capacitors with a tolerance of 10% or better are recommended for impedance matching and improved CMRR and PSRR. POWER DISSIPATION AND EFFICIENCY The major benefit of a Class D amplifier is increased efficiency versus a Class AB. The efficiency of the LM4674A is attributed to the region of operation of the transistors in the output stage. The Class D output stage acts as current steering switches, consuming negligible amounts of power compared to their Class AB counterparts. Most of the power loss associated with the output stage is due to the IR loss of the MOSFET on-resistance, along with switching losses due to gate charge. SHUTDOWN FUNCTION The LM4674A features independent left and right channel shutdown controls, allowing each channel to be disabled independently. /SDR controls the right channel, while /SDL controls the left channel. Driving either low disables the corresponding channel, reducing supply current to 0.03A. It is best to switch between ground and VDD for minimum current consumption while in shutdown. The LM4674A may be disabled with shutdown voltages in between GND and VDD, the idle current will be greater than the typical 0.03A value. Increased THD+N may also be observed when a voltage of less than VDD is applied to /SD_ for logic levels between GND and VDD Bypass /SD_ with a 0.1F capacitor. The LM4674A shutdown inputs have internal pulldown resistors. The purpose of these resistors is to eliminate any AUDIO AMPLIFIER GAIN SETTING The LM4674A features four internally configured gain settings. The device gain is selected through the two logic inputs, G0 and G1. The gain settings are as shown in the following table. G1 G0 GAIN V/V 13 dB 0 0 2 6 0 1 4 12 1 0 8 18 1 1 16 24 www.national.com LM4674A Application Information LM4674A Application Information The inductive nature of the transducer load can also result in overshoot on one of both edges, clamped by the parasitic diodes to GND and VDD in each case. From an EMI standpoint, this is an aggressive waveform that can radiate or conduct to other components in the system and cause interference. In is essential to keep the power and output traces short and well shielded if possible. Use of ground planes beads and micros-strip layout techniques are all useful in preventing unwanted interference. (Continued) PCB LAYOUT GUIDELINES As output power increases, interconnect resistance (PCB traces and wires) between the amplifier, load and power supply create a voltage drop. The voltage loss due to the traces between the LM4674A and the load results in lower output power and decreased efficiency. Higher trace resistance between the supply and the LM4674A has the same effect as a poorly regulated supply, increasing ripple on the supply line, and reducing peak output power. The effects of residual trace resistance increases as output current increases due to higher output power, decreased load impedance or both. To maintain the highest output voltage swing and corresponding peak output power, the PCB traces that connect the output pins to the load and the supply pins to the power supply should be as wide as possible to minimize trace resistance. As the distance from the LM4674A and the speaker increases, the amount of EMI radiation increases due to the output wires or traces acting as antennas become more efficient with length. Ferrite chip inductors places close to the LM4674A outputs may be needed to reduce EMI radiation. The use of power and ground planes will give the best THD+N performance. In addition to reducing trace resistance, the use of power planes creates parasitic capacitors that help to filter the power supply line. www.national.com 14 LM4674A Application Information (Continued) 20196126 Differential Input Configuration FIGURE 2. 15 www.national.com LM4674A Application Information (Continued) 20196138 Single-Ended Input Configuration FIGURE 3. www.national.com 16 LM4674A Revision Table Rev Date Description 1.0 9/13/06 Initial WEB release. 17 www.national.com LM4674A Filterless 2.5W Stereo Class D Audio Power Amplifier Physical Dimensions inches (millimeters) unless otherwise noted 16 Bump micro SMD Order Number LM4674ATL NS Package Number TLA1611A X1 = 2mm X2 = 2mm X3 = 0.6mm 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. For the most current product information visit us at www.national.com. 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. 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. BANNED SUBSTANCE COMPLIANCE National Semiconductor follows the provisions of the Product Stewardship Guide for Customers (CSP-9-111C2) and Banned Substances and Materials of Interest Specification (CSP-9-111S2) for regulatory environmental compliance. Details may be found at: www.national.com/quality/green. Lead free products are RoHS compliant. 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 Francais 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 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI's terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety-critical applications. TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated products in automotive applications, TI will not be responsible for any failure to meet such requirements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Applications Audio www.ti.com/audio Communications and Telecom www.ti.com/communications Amplifiers amplifier.ti.com Computers and Peripherals www.ti.com/computers Data Converters dataconverter.ti.com Consumer Electronics www.ti.com/consumer-apps DLP(R) Products www.dlp.com Energy and Lighting www.ti.com/energy DSP dsp.ti.com Industrial www.ti.com/industrial Clocks and Timers www.ti.com/clocks Medical www.ti.com/medical Interface interface.ti.com Security www.ti.com/security Logic logic.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Power Mgmt power.ti.com Transportation and Automotive www.ti.com/automotive Microcontrollers microcontroller.ti.com Video and Imaging RFID www.ti-rfid.com OMAP Mobile Processors www.ti.com/omap Wireless Connectivity www.ti.com/wirelessconnectivity TI E2E Community Home Page www.ti.com/video e2e.ti.com Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright (c) 2011, Texas Instruments Incorporated