LM48411 Ultra-Low EMI, Filterless, 2.5W, Stereo, Class D Audio Power Amplifier with E2S General Description Key Specifications The LM48411 is a single supply, high efficiency, 2.5W/channel Class D audio amplifier. The LM48411 features National's Enhanced Emissions Suppression (E2S) system, that features a unique patent-pending ultra low EMI, spread spectrum, PWM architecture, that significantly reduces RF emissions while preserving audio quality and efficiency. The E2S system improves battery life, reduces external component count, board area consumption, system cost, and simplifying design. The LM48411 is designed to meet the demands of mobile phones and other portable communication devices. Operating on a single 5V supply, it is capable of delivering 2.5W/ channel of continuous output power to a 4 load with less than 10% THD+N. Its flexible power supply requirements allow operation from 2.4V to 5.5V. The wide band spread spectrum architecture of the LM48411 reduces EMI-radiated emissions due to the modulator frequency. The LM48411 features high efficiency compared to a conventional Class AB amplifier. The E2S system includes an advanced, patent-pending edge rate control (ERC) architecture that further reduce emissions by minimizing the high frequency component of the device output, while maintaining high quality audio reproduction and high efficiency ( = 87% at VDD = 3.6V, PO = 500mW). Four gain options are pin selectable through GAIN0 and GAIN1 pins. The LM48411 features a low-power consumption shutdown mode. Shutdown may be enabled by driving the Shutdown pin to a logic low (GND). 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 control maximizes power savings in mixed mono/stereo applications. Efficiency at 3.6V, 500mW into 8 speaker 87% (typ) Efficiency at 3.6V, 100mW into 8 speaker 80% (typ) Efficiency at 5V, 1W into 8 speaker Quiescent current, 3.6V supply 88% (typ) 4.2mA (typ) Power Output at VDD = 5V RL = 4, THD 10% 2.5W (typ) Power Output at VDD = 5V RL = 8, THD 10% 1.5W (typ) Total shutdown power supply current Single supply range 0.01A (typ) 2.4V to 5.5V Features E2S system reduces EMI preserving Audio Quality and Efficiency Output short circuit protection Stereo Class D Operation No output filter required for inductive loads Logic selectable gain Independent shutdown control Minimum external components "Click and pop" suppression circuitry Micro-power shutdown mode Available in space-saving 0.5mm pitch micro SMD package Applications Mobile phones PDAs Portable electronic devices Boomer(R) is a registered trademark of National Semiconductor Corporation. (c) 2008 National Semiconductor Corporation 300095 www.national.com LM48411 Ultra-Low EMI, Filterless, 2.5W, Stereo, Class D Audio Power Amplifier with E2S July 3, 2008 LM48411 LM48411 RF Emissions 30009586 FIGURE 1. RF Emissions -- 3in cable www.national.com 2 LM48411 Typical Application 30009501 FIGURE 2. Typical Audio Amplifier Application Circuit 3 www.national.com LM48411 Connection Diagrams 16 Bump micro SMD Package micro SMD Marking 30009557 Top View X -- Date Code T-- Die Traceability G -- Boomer Family J2 -- LM48411TL 30009502 Top View Order Number LM48411TL See NS Package Number TLA16ACA Pin Descriptions www.national.com Bump Name A1 OUTLB Function Left Channel output B A2 SDL A3 PGND Left channel active low shutdown A4 OUTRB Right channel output B B1 OUTLA Left channel output A B2 SDR Power GND Right channel active low shutdown B3 AGND B4 OUTRA Ground C1 PVDD C2 G1 Gain setting input 1 C3 G0 Gain setting input 0 C4 AVDD Power supply D1 INL+ Non-inverting left channel input D2 INL- Inverting left channel input D3 INR- Inverting right channel input D4 INR+ Non-inverting right channel input Right channel output A Power VDD 4 63.6C/W JA (micro SMD) Soldering Information See AN-1112 "microSMD Wafers Level Chip Scale Package." If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (Note 1) Storage Temperature Voltage at Any Input Pin 6.0V -65C to +150C Operating Ratings VDD + 0.3V V GND - 0.3V Power Dissipation (Note 3) Internally Limited ESD Rating, all other pins (Note 4) 2.0kV ESD Rating (Note 5) 200V Junction Temperature (TJMAX) 150C (Notes 1, 2) Temperature Range TMIN TA TMAX Supply Voltage -40C TA 85C 2.4V VDD 5.5V Electrical Characteristics The following specifications apply for AV = 6dB, RL = 15H+8, f = 1kHz, unless otherwise specified. Limits apply for TA = 25C. VDD = 3.6V. LM48411 Symbol |VOS| IDD Parameter Differential Output Offset Voltage Quiescent Power Supply Current Conditions VI = 0V, AV = 2V/V, VDD = 2.4V to 5.0V Typical Limit (Note 6) (Notes 7, 8) 5 Units (Limits) mV VIN = 0V, No Load, VDD = 5.0V 5.1 7.5 mA (max) VIN = 0V, No Load, VDD = 3.6V 4.2 6.0 mA (max) VIN = 0V, No Load, VDD = 2.4V 3.0 4.5 mA (max) VIN = 0V, RL = 8, VDD = 5.0V 5.2 mA VIN = 0V, RL = 8, VDD = 3.6V 4.2 mA VIN = 0V, RL = 8, VDD = 2.4V 3.0 mA 0.01 A (max) ISD Shutdown Current VSDR = VSDL= GND VSDIH Shutdown voltage input high For SDR, SDL 1.4 V (min) VSDIL Shutdown voltage input low For SDR, SDL 0.4 V (max) 6 60.5 dB 12 120.5 dB 18 180.5 dB RL = 24 240.5 dB AV = 6dB 56 k AV = 12dB 37.5 k AV = 18dB 22.5 k AV = 24dB 12.5 k VSDR/SDL = 0.4V 4.2 ms GAIN0, GAIN1 = GND RL = GAIN0 = VDD, GAIN1 = GND AV Gain RL = GAIN0 = GND, GAIN1 = VDD RL = GAIN0, GAIN1 = VDD RIN TWU Input Resistance Wake Up Time 5 1.0 www.national.com LM48411 Thermal Resistance Absolute Maximum Ratings (Notes 1, 2) LM48411 LM48411 Symbol PO Parameter Output Power Conditions Typical Limit (Note 6) (Notes 7, 8) Units (Limits) RL = 15H + 4 + 15H THD = 10% (max) f = 1kHz, 22kHz BW VDD = 5V VDD = 3.6V VDD = 2.5V 2.5 1.2 530 W W mW RL = 15H + 4 + 15H THD = 1% (max) f = 1kHz, 22kHz BW VDD = 5V VDD = 3.6V VDD = 2.5V 2.0 1.0 430 W W mW VDD = 5V 1.5 W VDD = 3.6V 760 VDD = 2.5V 330 RL = 15H + 8 + 15H THD = 10% (max) f = 1kHz, 22kHz BW PO THD+N Output Power Total Harmonic Distortion + Noise Power Supply Rejection Ratio (Input Referred) mW (min) mW RL = 15H + 8 + 15H THD = 1% (max) f = 1kHz, 22kHz BW VDD = 5V 1.25 W VDD = 3.6V 615 mW VDD = 2.5V 270 mW PO = 500mW, f = 1kHz, RL = 8 0.05 % PO = 300mW, f = 1kHz, RL = 8 0.03 % 78 dB 77 dB VRipple = 200mVPP Sine, fRipple = 217Hz, VDD = 3.6, 5V PSRR 600 Inputs to AC GND, CI = 2F VRipple = 200mVPP Sine, fRipple = 1kHz, VDD = 3.6, 5V Inputs to AC GND, CI = 2F SNR Signal to Noise Ratio VDD = 5V, PO = 1WRMS 96 dB OUT Output Noise (Input Referred) VDD = 3.6V, A Weighted 22 VRMS CMRR Common Mode Rejection Ratio (Input Referred) VDD = 3.6V, VRipple = 1VPP Sine fRipple = 217Hz 64 dB Efficiency RL = 8 88 % Xtalk Crosstalk PO = 500mW, f = kHz 84 dB www.national.com VDD = 5V, POUT = 1W 6 Note 2: The Electrical Characteristics tables list guaranteed specifications under the listed Recommended Operating Conditions except as otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not guaranteed. 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 LMxxxxx, see Power Derating curves for additional information. Note 4: Human body model, applicable std. JESD22-A114C. Note 5: Machine model, applicable std. JESD22-A115-A. Note 6: Typical values represent most likely parametric norms at TA = +25C, and at the Recommended Operation Conditions at the time of product characterization and are not guaranteed. Note 7: Datasheet min/max specification limits are guaranteed by test or statistical analysis. Note 8: Shutdown current is measured in a normal room environment. Exposure to direct sunlight will increase ISD by a maximum of 2A. The Shutdown pin should be driven as close as possible to GND for minimal shutdown current and to VDD for the best THD performance in PLAY mode. See the Application Information section under SHUTDOWN FUNCTION for more information. Note 9: The performance graphs were taken using the Audio Precision AUX-0025 Switching Amplifier measurement Filter in series with the LC filter on the demo board. Typical Performance Characteristics THD+N vs Frequency VDD = 2.5V, RL = 8, PO = 100mW/channel AV = 6dB THD+N vs Frequency VDD = 3.6V, RL = 8, PO = 250mW/channel AV = 6dB 30009546 30009540 THD+N vs Frequency VDD = 5.0V, RL = 8, PO = 375mW/channel AV = 6dB THD+N vs Frequency VDD = 2.5V, RL = 4, PO = 100mW/channel AV = 6dB 30009549 30009552 7 www.national.com LM48411 Note 1: "Absolute Maximum Ratings" indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability and/or performance. Functional operation of the device and/or non-degradation at the Absolute Absolute Maximum Ratings or other conditions beyond those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating Conditions indicate conditions at which the device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect to the ground pin, unless otherwise specified LM48411 THD+N vs Frequency VDD = 3.6V, RL = 4, PO = 250mW/channel AV = 6dB THD+N vs Frequency VDD = 5.0V, RL = 4, PO = 375mW/channel AV = 6dB 30009556 30009558 THD+N vs Output Power VDD = 2.5V, RL = 8, AV = 6dB THD+N vs Output Power VDD = 2.5V, RL = 8, AV = 24dB 30009574 30009575 THD+N vs Output Power VDD = 3.6V, RL = 8, AV = 6dB THD+N vs Output Power VDD = 3.6V, RL = 8, AV = 24dB 30009578 www.national.com 30009579 8 LM48411 THD+N vs Output Power VDD = 5V, RL = 8, AV = 6dB THD+N vs Output Power VDD = 5V, RL = 8, AV = 24dB 30009583 30009582 THD+N vs Output Power VDD = 2.5V, RL = 4, AV = 6dB THD+N vs Output Power VDD = 2.5V, RL = 4, AV = 24dB 30009572 30009573 THD+N vs Output Power VDD = 3.6V, RL = 4, AV = 6dB THD+N vs Output Power VDD = 3.6V, RL = 4, AV = 24dB 30009576 30009577 9 www.national.com LM48411 THD+N vs Output Power VDD = 5.0V, RL = 4, AV = 6dB THD+N vs Output Power VDD = 5.0V, RL = 4, AV = 24dB 30009580 30009581 PSRR vs Frequency VDD = 3.6V, RL = 8 CMRR vs Frequency VDD = 3.6V, RL = 8 30009568 30009571 Quiescent Current vs Power Supply RL = Output Power vs Supply Voltage RL = 4, f = 1kHz 30009561 30009542 www.national.com 10 LM48411 Output Power vs Supply Voltage RL = 8, f = 1kHz Efficiency vs Output Power RL = 4 30009562 30009569 Efficiency vs Output Power RL = 8 Crosstalk vs Frequency VDD = 3.6V, RL = 8 30009563 30009570 Power Dissipation vs Output Power RL = 4 Power Dissipation vs Output Power RL = 8 30009567 30009566 11 www.national.com LM48411 External Components Description (Figure 2) 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 12 GENERAL AMPLIFIER FUNCTION The LM48411 features a filterless modulation scheme. The differential outputs of the device switch at 300kHz from VDD to GND. When there is no input signal applied, the two outputs (VO1 and VO2) switch with a 50% duty cycle, with both outputs in phase. Because the outputs of the LM48411 are differential, the two signals cancel each other. This results in no net voltage across the speaker, thus there is no load current during an idle state, conserving power. With an input signal applied, the duty cycle (pulse width) of the LM48411 outputs changes. For increasing output voltages, the duty cycle of VO1 increases, while the duty cycle of VO2 decreases. For decreasing output voltages, the converse occurs, the duty cycle of VO2 increases while the duty cycle of VO1 decreases. The difference between the two pulse widths yields the differential output voltage. DIFFERENTIAL AMPLIFIER EXPLANATION As logic supply voltages continue to shrink, designers are increasingly turning to differential analog signal handling to preserve signal to noise ratios with restricted voltage swing. The LM48411 is a fully differential amplifier that features differential input and output stages. A differential amplifier amplifies the difference between the two input signals. Traditional audio power amplifiers have typically offered only singleended inputs resulting in a 6dB reduction in signal to noise ratio relative to differential inputs. The LM48411 also offers the possibility of DC input coupling which eliminates the two external AC coupling, DC blocking capacitors. The LM48411 can be used, however, as a single ended input amplifier while still retaining it's fully differential benefits. In fact, completely unrelated signals may be placed on the input pins. The LM48411 simply amplifies the difference between the signals. A major benefit of a differential amplifier is the improved common mode rejection ratio (CMRR) over single input amplifiers. The common-mode rejection characteristic of the differential amplifier reduces sensitivity to ground offset related noise injection, especially important in high noise applications. SPREAD SPECTRUM MODULATION The LM48411 features a fitlerless spread spectrum modulation scheme that eliminates the need for output filters, ferrite beads or chokes. The switching frequency varies by 30% about a 300kHz center frequency, reducing the wideband spectral contend, improving EMI emissions radiated by the speaker and associated cables and traces. Where a fixed frequency class D exhibits large amounts of spectral energy at multiples of the switching frequency, the spread spectrum architecture of the LM48411 spreads that energy over a larger bandwidth. The cycle-to-cycle variation of the switching period does not affect the audio reproduction of efficiency. PCB LAYOUT CONSIDERATIONS As output power increases, interconnect resistance (PCB traces and wires) between the amplifier, load and power supply create a voltage drop. The voltage loss on the traces between the LM48411 and the load results is lower output power and decreased efficiency. Higher trace resistance between the supply and the LM48411 has the same effect as a poorly regulated supply, increased ripple on the supply line also reducing the 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. The use of power and ground planes will give the best THD +N performance. While reducing trace resistance, the use of power planes also creates parasite capacitors that help to filter the power supply line. The inductive nature of the transducer load can also result in overshoot on one or 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. It is essential to keep the power and output traces short and well shielded if possible. Use of ground planes, beads, and micro-strip layout techniques are all useful in preventing unwanted interference. As the distance from the LM48411 and the speaker increase, the amount of EMI radiation will increase since the output wires or traces acting as antenna become more efficient with length. What is acceptable EMI is highly application specific. Ferrite chip inductors placed close to the LM48411 may be needed to reduce EMI radiation. The value of the ferrite chip is very application specific. ENHANCED EMISSIONS SUPPRESSION SYSTEM (E2S) The LM48411 features National's patent-pending E2S system that reduces EMI, while maintaining high quality audio reproduction and efficiency. The E2S system features a synchronizable oscillator with selectable spread spectrum, and advanced edge rate control (ERC). The LM48411 ERC greatly reduces the high frequency components of the output square waves by controlling the output rise and fall times, slowing the transitions to reduce RF emissions, while maximizing THD+N and efficiency performance. POWER DISSIPATION AND EFFICIENCY In general terms, efficiency is considered to be the ratio of useful work output divided by the total energy required to produce it with the difference being the power dissipated, typically, in the IC. The key here is "useful" work. For audio systems, the energy delivered in the audible bands is considered useful including the distortion products of the input signal. Sub-sonic (DC) and super-sonic components (>22kHz) are not useful. The difference between the power flowing from the power supply and the audio band power being transduced is dissipated in the LM48411 and in the transducer load. The amount of power dissipation in the LM48411 is very low. This is because the ON resistance of the switches used to form the output waveforms is typically less than 0.25. This leaves only the transducer load as a potential "sink" for the small excess of input power over audio band output power. The LM48411 dissipates only a fraction of the excess power requiring no additional PCB area or copper plane to act as a heat sink. 13 www.national.com LM48411 Application Information LM48411 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 LM48411. The input capacitors create a highpass filter with the input resistance Ri. The -3dB point of the high pass filter is found using Equation 1 below. SHUTDOWN FUNCTION In order to reduce power consumption while not in use, the LM48411 contains shutdown circuitry that reduces current draw to less than 0.01A. The trigger point for shutdown is shown as a typical value in the Electrical Characteristics Tables and in the Shutdown Hysteresis Voltage graphs found in the Typical Performance Characteristics section. It is best to switch between ground and supply for minimum current usage while in the shutdown state. While the LM48411 may be disabled with shutdown voltages in between ground and supply, the idle current will be greater than the typical 0.01A value. The LM48411 has an internal resistor connected between GND and Shutdown pins. The purpose of this resistor is to eliminate any unwanted state changes when the Shutdown pin is floating. The LM48411 will enter the shutdown state when the Shutdown pin is left floating or if not floating, when the shutdown voltage has crossed the threshold. To minimize the supply current while in the shutdown state, the Shutdown pin should be driven to GND or left floating. If the Shutdown pin is not driven to GND, the amount of additional resistor current due to the internal shutdown resistor can be found by Equation (1) below. (VSD - GND) / 300k f = 1 / 2RiCi (2) 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 LM48411 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, 217 Hz 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. AUDIO AMPLIFIER GAIN SETTING The LM48411 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. (1) With only a 0.5V difference, an additional 1.7A of current will be drawn while in the shutdown state. LOGIC INPUT 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 LM48411 supply pins. A 1F capacitor is recommended. GAIN G1 G0 V/V 0 0 2 6 0 1 4 12 1 0 8 18 1 1 16 24 Build of Materials Designator Footprint Quantity C1, C2 Ceramic Capacitor 0.1F, 50V, 10% 805 2 C3 - C6 Tantalum Capacitors 1F 20V, 10%, Size A 1206 4 Tantalum Capacitors 10F 20V, 10% Size B 1411 1 C11 Description JP1-5, JP8-11 Jumper Header Vertical Mount 2X1 0.100 9 JP6, JP7 Jumper Header Vertical Mount 3x1 0.100 2 www.national.com 14 dB LM48411 Demonstration Board Schematic 30009592 15 www.national.com LM48411 Demonstration Board Layout 30009591 Top Silkscreen Layer 30009590 Top Layer 30009588 Mid 1 Layer www.national.com 16 LM48411 30009589 Mid 2 Layer 30009587 Bottom Layer 17 www.national.com LM48411 Revision History Rev Date 1.0 09/21/07 Initial release. 1.1 10/01/07 Fixed few typos. 1.2 11/30/07 Added the demo boards and BOM. 1.3 12/19/07 Edited the 16-bump micro SMD package diagram and the Pin Description table. 1.4 01/08/08 Edited the 16-bump micro SMD package diagram. 1.5 06/27/08 Text edits. 1.6 07/03/08 Text edits (under SHUTDOWN FUNCTION). www.national.com Description 18 LM48411 Physical Dimensions inches (millimeters) unless otherwise noted 16 Bump micro SMD Order Number LM48411TL NS Package Number TLA16ACA X1 = 1.996mm X2 = 2.047mm X3 = 0.6mm 19 www.national.com LM48411 Ultra-Low EMI, Filterless, 2.5W, Stereo, Class D Audio Power Amplifier with E2S Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH www.national.com/webench Audio www.national.com/audio Analog University www.national.com/AU Clock Conditioners www.national.com/timing App Notes www.national.com/appnotes Data Converters www.national.com/adc Distributors www.national.com/contacts Displays www.national.com/displays Green Compliance www.national.com/quality/green Ethernet www.national.com/ethernet Packaging www.national.com/packaging Interface www.national.com/interface Quality and Reliability www.national.com/quality LVDS www.national.com/lvds Reference Designs www.national.com/refdesigns Power Management www.national.com/power Feedback www.national.com/feedback Switching Regulators www.national.com/switchers LDOs www.national.com/ldo LED Lighting www.national.com/led PowerWise www.national.com/powerwise Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors Wireless (PLL/VCO) www.national.com/wireless THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION ("NATIONAL") PRODUCTS. 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