LM48311TLX

LM48311 Ultra-Low EMI, Filterless, 2.6W, Mono, Class D Audio Power Amplifier with E2S LM48311  June 25, 2009 Ultra-Low EMI, Filterless, 2.6W, Mono, Class D Audio Power Amplifier with E2S General Description The LM48311 is a single supply, high efficiency, mono, 2.6W, filterless switching audio amplifier. The LM48311 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 LM48311 is designed to meet the demands of portable multimedia devices. Operating from a single 5V supply, the device is capable of delivering 2.6W of continuous output power to a 4Ω load with less than 10% THD+N. Flexible power supply requirements allow operation from 2.4V to 5.5V. The LM48311 features both a spread spectrum modulation scheme, and an advanced, patented edge rate control (ERC) architecture that significantly reduces emissions, while maintaining high quality audio reproduction (THD+N = 0.03%) and high efficiency (η = 88%). The LM48311 features high efficiency compared to conventional Class AB amplifiers, and other low EMI Class D amplifiers. When driving and 8Ω speaker from a 5V supply, the device operates with 88% efficiency at PO = 1W. The gain of the LM48311 is internally set to 6dB, further reducing external component count. A low power shutdown mode reduces supply current consumption to 0.01µA. Advanced output short circuit protection with auto-recovery prevents the device from being damaged during fault conditions. Superior click and pop suppression eliminates audible transients on power-up/down and during shutdown. Key Specifications ■ Efficiency at 3.6V, 400mW into 8Ω ■ Efficiency at 5V, 1W into 8Ω ■ Quiescent Power Supply Current at 5V ■ Power Output at VDD = 5V, RL = 4Ω THD+N ≤ 10% THD+N ≤ 1% ■ Power Output at VDD = 5V, RL = 8Ω THD+N ≤ 10% THD+N ≤ 1% ■ Shutdown current 85% (typ) 88% (typ) 3.1mA 2.6W (typ) 2.1W (typ) 1.6W (typ) 1.3W (typ) 0.01μA (typ) Features ■ Passes FCC Class B Radiated Emissions with 20 inches of cable ■ E2S System Reduces EMI while Preserving Audio Quality ■ ■ ■ ■ ■ ■ ■ ■ and Efficiency Output Short Circuit Protection with Auto-Recovery No output filter required Internally Configured Gain (6dB) Low power shutdown mode Minimum external components "Click and pop" suppression Micro-power shutdown Available in space-saving microSMD package Applications ■ Mobile phones ■ PDAs ■ Laptops Boomer® is a registered trademark of National Semiconductor Corporation. © 2009 National Semiconductor Corporation 300975 www.national.com LM48311 Typical Application 300975a8 FIGURE 1. Typical Audio Amplifier Application Circuit www.national.com 2 LM48311 Connection Diagrams TL Package 1.539mm x 1.565mm x 0.6mm 9–Bump micro SMD Marking 300975a7 Top View X = Date Code T = Die Traceability G = Boomer Family N1 = LM48311TL 300975a3 Top View Order Number LM48311TL See NS Package Number TLA09BCA Ordering Information Order Number LM48311TL LM48311TLX Package 9 Bump micro SMD 9 Bump micro SMD Package DWG # TLA09BCA TLA09BCA Transport Media 250 units on tape and reel 3000 units on tape and reel MSL Level 1 1 Green Status RoHS & no Sb/Br RoHS & no Sb/Br Pin Descriptions TABLE 1. Bump Description Pin A1 A2 A3 B1 B2 B3 C1 C2 C3 Name IN+ SD OUTA VDD PVDD PGND INGND OUTB Non-Inverting Input Active Low Shutdown Input. Connect to VDD for normal operation. Non-Inverting Output Power Supply H-Bridge Power Supply Power Ground Inverting Input Ground Inverting Output Description 3 www.national.com LM48311 Absolute Maximum Ratings (Notes 1, 2) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Storage Temperature Input Voltage Power Dissipation (Note 3) ESD Rating (Note 4) ESD Rating (Note 5) 6.0V −65°C to +150°C − 0.3V to VDD +0.3V Internally Limited 2000V 200V Junction Temperature Thermal Resistance 150°C 70°C/W  θJA Soldering Information See AN-1112 "Micro SMD Wafer Level Chip Scale Package." Operating Ratings Temperature Range TMIN ≤ TA ≤ TMAX Supply Voltage (VDD, PVDD) (Notes 2, 8) (Notes 1, 2) −40°C ≤ TA ≤ +85°C 2.4V ≤ VDD ≤ 5.5V The following specifications apply for AV = 6dB, RL = 8Ω, f = 1kHz, unless otherwise specified. Limits apply for TA = 25°C. LM48311 Symbol VDD IDD ISD VOS VIH VIL CMVR TWU fSW AV RIN RSD Parameter Supply Voltage Range Quiescent Power Supply Current Shutdown Current Differential Output Offset Voltage Logic Input High Voltage Logic Input Low Voltage Common Mode Input Voltage Range Wake Up Time Switching Frequency Gain Input Resistance Input Resistance (SD) SD to GND RL = 4Ω, THD = 10% f = 1kHz, 22kHz BW VDD = 5V VDD = 3.6V VDD = 2.5V RL = 8Ω, THD = 10% f = 1kHz, 22kHz BW VDD = 5V VDD = 3.6V VDD = 2.5V RL = 4Ω, THD = 1% f = 1kHz, 22kHz BW VDD = 5V VDD = 3.6V VDD = 2.5V RL = 8Ω, THD = 1% f = 1kHz, 22kHz BW VDD = 5V VDD = 3.6V VDD = 2.5V THD+N Total Harmonic Distortion + Noise PO = 200mW, RL = 8Ω, f = 1kHz PO = 100mW, RL = 8Ω, f = 1kHz 4 Electrical Characteristics VDD = PVDD = 5V Conditions VIN = 0 VIN = 0, RL = ∞ VDD = 3.6V VDD = 5V Shutdown enabled VIN = 0 Min (Note 7) 2.4 Typ (Note 6) Max (Note 7) 5.5 Units (Limits) V mA mA μA mV V V V ms kHz 2.7 3.1 0.01 –3 1.4 1 3.4 3.9 1.0 3 0.4 0 7.5 SYNC_IN = VDD (Spread Spectrum) 5 17 300±30 6 20 300 VDD–0.25 7 dB kΩ kΩ 2.6 1.3 555 W W mW PO Output Power 1.6 800 354 W mW mW 2.1 1 446 W W mW 1.1 1.3 640 286 0.03 0.03 W (min) mW mW % % www.national.com LM48311 LM48311 Symbol Parameter Conditions VRIPPLE = 200mVP-P Sine, PSRR Power Supply Rejection Ratio (Input Referred) Common Mode Rejection Ratio (Input Referred) Efficiency Signal to Noise Ratio Output Noise (Input Referred) Inputs AC GND, CIN = 1μF fRIPPLE = 217Hz fRIPPLE = 1kHz VRIPPLE = 1VP-P fRIPPLE = 217Hz VDD = 5V, POUT = 1W VDD = 3.6V, POUT = 400mW PO = 1W Un-weighted A-weighted 78 76 86 88 85 97 28 22 Min (Note 7) Typ (Note 6) Max (Note 7) Units (Limits) dB dB dB % % dB μV μV CMRR η SNR εOS 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 Maximum Ratings or other conditions beyond those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating Conditionsindicate 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. 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, 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, applicable std. JESD22-A114C. Note 5: Machine model, applicable std. JESD22-A115-A. Note 6: Typical values represent most likely parametric norms at TA = +25°C, 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: RL is a resistive load in series with two inductors to simulate an actual speaker load. For RL = 8Ω, the load is 15µH + 8Ω, +15µH. For RL = 4Ω, the load is 15µH + 4Ω + 15µH. 30097528 FIGURE 2. PSRR Test Circuit 30097527 FIGURE 3. CMRR Test Circuit 5 www.national.com LM48311 Typical Performance Characteristics For all performance graphs, the Output Gains are set to 0dB, unless otherwise noted. THD+N vs Frequency VDD = 2.5V, PO = 250mW, RL = 4Ω THD+N vs Frequency VDD = 3.6V, PO = 600mW, RL = 4Ω 30097504 30097505 THD+N vs Frequency VDD = 5 .0V, PO = 1.2W, RL = 4Ω THD+N vs Frequency VDD = 2.5V, PO = 175mW, RL = 8Ω 30097506 30097507 THD+N vs Frequency VDD = 3.6V, PO = 400mW, RL = 8Ω THD+N vs Frequency VDD = 3.6V, PO = 600mW, RL = 8Ω 30097508 30097509 www.national.com 6 LM48311 THD+N vs Frequency VDD = 3.6V, PO = 1.25W, RL = 3Ω THD+N vs Output Power f = 1kHz, RL = 4Ω 30097510 30097501 THD+N vs Output Power f = 1kHz, RL = 8Ω THD+N vs Output Power f = 1kHz, RL = 3Ω 30097502 30097503 Efficiency vs Output Power f = 1kHz, RL = 4Ω Efficiency vs Output Power f = 1kHz, RL = 8Ω 30097511 30097512 7 www.national.com LM48311 Power Dissipation vs Output Power f = 1kHz, RL = 4Ω Power Dissipation vs Output Power f = 1kHz, RL = 8Ω 30097513 30097514 Output Power vs Supply Voltage f = 1kHz, RL = 4Ω Output Power vs Supply Voltage f = 1kHz, RL = 8Ω 30097515 30097516 CMRR vs Frequency VDD= 5.0V, VRIPPLE = 1VP-P, RL = 8Ω PSRR vs Frequency VDD= 5.0V, VRIPPLE = 200mVP-P, RL = 8Ω 30097529 30097517 www.national.com 8 LM48311 Spread Spectrum Output Spectrum vs Frequency VDD= 5.0V, VIN = 1VRMS, RL = 8Ω Wideband Spread Spectrum Output Spectrum vs Frequency VDD= 5.0V, RL = 8Ω 30097519 30097520 Supply Current vs Supply Voltage No Load Shutdown Supply Current vs Supply Voltage No Load 30097521 30097522 9 www.national.com LM48311 Application Information GENERAL AMPLIFIER FUNCTION The LM48311 mono 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 (VOUTA and VOUTB) 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. With the input signal applied, the duty cycle (pulse width) of the LM48311 outputs changes. For increasing output voltage, the duty cycle of VOUTA increases, while the duty cycle of VOUTB decreases. For decreasing output voltages, the converse occurs. The difference between the two pulse widths yields the differential output voltage. ENHANCED EMISSIONS SUPPRESSION SYSTEM (E2S) The LM48311 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 LM48311 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. The overall result of the E2S system is a filterless Class D amplifier that passes FCC Class B radiated emissions standards with 20in of twisted pair cable, with excellent 0.03% THD+N and high 88% efficiency. SPREAD SPECTRUM The spread spectrum modulation reduces the need for output filters, ferrite beads or chokes. The switching frequency varies randomly 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 LM48311 spreads that energy over a larger bandwidth (See Typical Performance Characteristics). The cycle-to-cycle variation of the switching period does not affect the audio reproduction, efficiency, or PSRR. 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 LM48311 features a fully differential speaker amplifier. 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 LM48311 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 POWER DISSIPATION AND EFFICIENCY The major benefit of a Class D amplifier is increased efficiency versus a Class AB. The efficiency of the LM48311 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 onresistance, along with switching losses due to gate charge. SHUTDOWN FUNCTION The LM48311 features a low current shutdown mode. Set SD = GND to disable the amplifier and reduce supply current to 0.01µA. Switch SD between GND and VDD for minimum current consumption is shutdown. The LM48311 may be disabled with shutdown voltages in between GND and VDD, the idle current will be greater than the typical 0.1µA value. Increased THD +N may also be observed when a voltage of less than VDD is applied to SD. The LM48311 shutdown input has and internal pulldown resistor. The purpose of this resistor is to eliminate any 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. AUDIO AMPLIFIER POWER SUPPLY BYPASSING/ FILTERING Proper power supply bypassing is critical for low noise performance and high PSRR. Place the supply bypass capacitors as close to the device as possible. Typical applications employ a voltage regulator with 10µF and 0.1µF bypass capacitors that increase supply stability. These capacitors do not eliminate the need for bypassing of the LM48311 supply pins. A 1µF capacitor is recommended. 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 LM48311. The input capacitors create a highpass filter with the input resistors RIN. The -3dB point of the high pass filter is found using Equation (1) below. f = 1 / 2πRINCIN Where RIN is the value of the input resistor given in the Electrical Characteristics table. 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 LM48311 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. AUDIO AMPLIFIER GAIN The gain of the LM48311 is internally set to 6dB. The gain can be reduced by adding additional input resistance (Figure 6). In this configuration, the gain of the device is given by: www.national.com 10 LM48311 AV = 2 x [RF / (RINEXT + RIN)] Where RF is 40kΩ, RIN is 20kΩ, and RINEXT is the value of the additional external resistor. used to block and DC component at the input of the device. Figure 5 shows the typical single-ended applications circuit. 30097561 FIGURE 4. Reduced Gain Configuration SINGLE-ENDED AUDIO AMPLIFIER CONFIGURATION The LM48311 is compatible with single-ended sources. When configured for single-ended inputs, input capacitors must be 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 LM48311 and the load results in lower output power and decreased efficiency. Higher trace resistance between the supply and the LM48311 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. The use of power and ground planes will give the best THD +N performance. In addition to reducing trace resistance, the BUILD OF MATERIALS 300975a6 FIGURE 5. Single-Ended Input Configuration use of power planes creates parasitic capacitors that help to filter the power supply line. 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. wires or traces acting as antennas become more efficient with length. Ferrite chip inductors places close to the LM48311 outputs may be needed to reduce EMI radiation. LM48311TL Demoboard Bill of Materials Designator C1 C2 C3, C4 JU1 LM48311TL Quantity 1 1 2 1 1 Description 10µF ±10% 16V Tantalum Capacitor (B Case) AVX TPSB106K016R0800 1µF ±10% 16V X5R Ceramic Capacitor (603) Panasonic ECJ-1VB1C105K 1µF ±10% 16V X7R Ceramic Capacitor (1206) Panasonic ECJ-3YB1C105K 3-Pin Header LM48311TL (9-Bump microSMD) 11 www.national.com LM48311 LM48311 Demo Board Schematic 30097530 FIGURE 6. LM48311 DEMO BOARD SCHEMATIC www.national.com 12 LM48311 Demo Boards 30097526 30097525 FIGURE 7. Top Silkscreen FIGURE 8. Top Layer 30097524 30097523 FIGURE 9. Bottom Silkscreen FIGURE 10. Bottom Layer 13 www.national.com LM48311 Revision History Rev 1.0 Date 06/25/09 Initial released. Description www.national.com 14 LM48311 Physical Dimensions inches (millimeters) unless otherwise noted 9 Bump micro SMD Order Number LM48311TL NS Package Number TLA09BCA X1 = 1.539mm X2 = 1.565mm X3 = 0.6mm 15 www.national.com LM48311 Ultra-Low EMI, Filterless, 2.6W, Mono, 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 Amplifiers Audio Clock and Timing Data Converters Interface LVDS Power Management Switching Regulators LDOs LED Lighting Voltage Reference PowerWise® Solutions Temperature Sensors Wireless (PLL/VCO) www.national.com/amplifiers www.national.com/audio www.national.com/timing www.national.com/adc www.national.com/interface www.national.com/lvds www.national.com/power www.national.com/switchers www.national.com/ldo www.national.com/led www.national.com/vref www.national.com/powerwise WEBENCH® Tools App Notes Reference Designs Samples Eval Boards Packaging Green Compliance Distributors Quality and Reliability Feedback/Support Design Made Easy Solutions Mil/Aero PowerWise® Design University Design Support www.national.com/webench www.national.com/appnotes www.national.com/refdesigns www.national.com/samples www.national.com/evalboards www.national.com/packaging www.national.com/quality/green www.national.com/contacts www.national.com/quality www.national.com/feedback www.national.com/easy www.national.com/solutions www.national.com/milaero www.national.com/solarmagic www.national.com/training Serial Digital Interface (SDI) www.national.com/sdi www.national.com/wireless www.national.com/tempsensors SolarMagic™ THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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