LM48556 Fully Differential, Mono, Ceramic Speaker Driver General Description Key Specifications The LM48556 is a single supply, mono, ceramic speaker driver with an integrated charge-pump, designed for portable devices, such as cell phones, where board space is at a premium. The LM48556 charge pump allows the device to deliver 17.5VPP (typ) from a single 4.5V supply. Additionally, the charge pump features a soft start function that minimizes transient current during power-up. The LM48556 features high power supply rejection ratio (PSRR) of 80dB at 217Hz, allowing the device to operate in noisy environments without additional power supply conditioning. Flexible power supply requirements allow operation from 2.7V to 5.0V. Additionally, the LM48556 features a differential input function and an externally configurable gain. A low power shutdown mode reduces supply current consumption to 0.1μA. Superior click and pop suppression eliminates audible transients on power-up/down and during shutdown. The LM48556 is available in an ultra-small 12-bump micro SMD package (2mm x 1.5mm). ■ Output Voltage Swing VDD = 3.6V, 1kHz 14.2VPP (typ) VDD = 4.5V, 1kHz 17.5VPP (typ) ■ Power Supply Rejection Ratio f = 217Hz, VDD = 3.6V 80dB (typ) ■ IDD at VDD = 3.6V 4.8mA (typ) ■ Wake-Up Time 0.5ms (typ) Features ■ ■ ■ ■ ■ Fully differential amplifier Externally configurable gain Integrated charge pump Low power shutdown mode Soft start function Applications ■ Mobile phones ■ PDA's ■ Digital cameras Boomer® is a registered trademark of National Semiconductor Corporation. © 2008 National Semiconductor Corporation 300572 www.national.com LM48556 Fully Differential, Mono, Ceramic Speaker Driver December 10, 2008 LM48556 Typical Application 300572d4 FIGURE 1. Typical Audio Amplifier Application Circuit www.national.com 2 LM48556 Connection Diagrams 12 Bump micro SMD 300572d6 Top View Order Number LM48556TL, LM48556TLX See NS Package Number TLA121AA 12 Bump micro SMD Package View 30057231 3 www.national.com LM48556 LM48556TL Marking 300572d5 Top View XY = Date Code TT = Lot Traceability G = Boomer Family K4 = LM48556TL Bump Descriptions Bump Name Description A1 OUT- Amplifier Inverting Output A2 SVDD Signal Power Supply - Positive A3 IN+ Amplifier Non-inverting Input B1 SVSS Signal Power Supply - Negative B2 OUT+ Amplifier Non-inverting Output B3 IN- C1 CPVSS C2 C1P Charge Pump Flying Capacitor Positive Terminal C3 SD Active Low Reset Input. Connect to VDD for normal operation. Drive SD low to disable. Amplifier Inverting Input Charge Pump Output Voltage D1 C1N D2 PGND Charge Pump Flying Capacitor Negative Terminal Power Ground D3 PVDD Power Supply Ordering Information Order Number Package Package Dwg # Transport Media MSL Green Status LM48556TL 12 bump micro SMD TLA121AA 250 units on tape and reel 1 RoHS and no Sb/Br LM48556TLX 12 bump micro SMD TLA121AA 3000 units on tape and reel 1 RoHS and no Sb/Br www.national.com 4 Features If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (SVDD, PVDD) (Note 1) Storage Temperature Input Voltage Power Dissipation (Note 3) ESD Rating(Note 4) ESD Rating (Note 5) 114°C/W θJA (TL) Soldering Information See AN-1112 Micro SMD Wafer Level Chip Scale 5.25V −65°C to +150°C −0.3V to VDD + 0.3V Internally limited 2000V 200V Electrical Characteristics VDD = 3.6V 150°C Operating Ratings Temperature Range TMIN ≤ TA ≤ TMAX −40°C ≤ TA ≤ +85°C 2.7V ≤ _VDD ≤ 5.0V Supply Voltage (SVDD, PVDD) (Note 2) The following specifications apply for VDD = 3.6V, AV-BTL = 20dB (R F = 200kΩ, RIN = 20kΩ), ZL = 15Ω+1μF, unless otherwise specified. Limits apply for TA = 25°C. LM48556 Symbol Parameter Conditions Typical (Note 6) Limit (Note 7) Units (Limits) IDD Quiescent Power Supply Current VIN = 0V 4.8 7 ISD Shutdown Current VSD = GND (Note 8) 0.1 1 µA (max) VOS Output Offset Voltage CIN = 0.47μF, AV = 1V/V (0dB) 0.6 4 mV (max) TWU Wake-up Time 0.5 ms THD+N = 1% (max); f = 1kHz 14.2 VPP THD+N = 1% (max); f = 10kHz 11.5 VOUT Output Voltage Swing 11 mA (max) VPP (min) VOUT = 11VPP, f = 1kHz THD+N Total Harmonic Distortion + Noise AV = 0dB 0.005 % AV = 20dB 0.03 % μV εOS Output Noise A-weighted filter, VIN = 0V Input referred 8 PSRR Power Supply Rejection Ratio VRIPPLE = 200mVPP, f = 217Hz 80 CMRR Common Mode Rejection Ratio Input Referred 70 VLH Logic High Threshold Voltage 1.2 V (min) VLL Logic Low Threshold Voltage 0.45 V (max) Electrical Characteristics VDD = 4.5V 60 dB (min) 60 dB (min) (Note 2) The following specifications apply for VDD = 4.5V, AV-BTL = 20dB (R F = 200kΩ, RIN = 20kΩ), ZL = 15Ω+1μF, unless otherwise specified. Limits apply for TA = 25°C. LM48556 Symbol Parameter Conditions Typical (Note 6) Limit (Note 7) Units (Limits) IDD Quiescent Power Supply Current VIN = 0V 6.5 10 mA (max) ISD Shutdown Current VSD = GND (Note 8) 0.1 1 µA (max) VOS Output Offset Voltage CIN = 0.47μF, AV = 1V/V (0dB) 0.6 4 mV (max) TWU Wake-up Time VOUT Output Voltage Swing THD+N Total Harmonic Distortion + Noise 0.5 THD+N = 1% (max); f = 1kHz 17.5 THD+N = 1% (max); f = 10kHz 14.6 ms (max) VPP 14 VPP (min) VOUT = 14VPP, f = 1kHz εOS Output Noise AV = 0dB 0.005 % AV = 20dB 0.03 % 8 μV A-weighted filter, VIN = 0V Input referred 5 www.national.com LM48556 Junction Temperature Thermal Resistance Absolute Maximum Ratings (Notes 1, 2) LM48556 LM48556 Symbol Parameter Conditions Typical (Note 6) Limit (Note 7) Units (Limits) PSRR Power Supply Rejection Ratio VRIPPLE = 200mVPP, f = 217Hz, 80 60 dB (min) CMRR Common Mode Rejection Ratio Input Referred 70 60 dB (min) VLH Logic High Threshold Voltage 1.2 V (min) VLL Logic Low Threshold Voltage 0.45 V (max) 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 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. 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 = +25ºC, 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. The SD pin should be driven as close as possible to GND for minimum shutdown current. www.national.com 6 LM48556 Typical Performance Characteristics ( ZL = 15Ω+1μF, AV = 20dB, BW = 22kHz) THD+N vs Frequency VDD = 2.7V, VO = 8VPP THD+N vs Frequency VDD = 3.6V, VO = 14.2VPP 300572e2 300572e1 THD+N vs Frequency VDD = 4.5V, VO = 17.5VPP THD+N vs Output Voltage Swing VDD = 2.7V, f = 1kHz 300572d9 300572d8 THD+N vs Output Voltage Swing VDD = 3.6V, f = 1kHz THD+N vs Output Voltage Swing VDD = 4.5V, f = 1kHz 300572d7 300572e0 7 www.national.com LM48556 CMRR vs Frequency VDD = 2.7V, Input referred CMRR vs Frequency VDD = 3.6V, Input referred 300572d0 300572d1 CMRR vs Frequency VDD = 4.5V, Input referred PSRR vs Frequency VDD = 2.7V, Input referred 300572d2 30057274 PSRR vs Frequency VDD = 3.6V, Input referred PSRR vs Frequency VDD = 4.5V, Input referred 30057276 30057275 www.national.com 8 LM48556 Output Voltage vs Frequency VDD = 2.7V, THD+N = 1% Output Voltage vs Frequency VDD = 3.6V, THD+N = 1% 300572e8 300572e9 Output Voltage vs Frequency VDD = 4.5V, THD+N = 1% Supply Current vs Supply Voltage VIN = GND, No Load 300572e3 300572f0 Power Consumption vs Output Voltage Swing VDD = 2.7V, THD+N ≤ 1% Power Consumption vs Output Voltage Swing VDD = 3.6V, THD+N ≤ 1% 300572e4 300572e5 9 www.national.com LM48556 Power Consumption vs Output Voltage Swing VDD = 4.5V, THD+N ≤ 1% 300572e6 www.national.com 10 GENERAL AMPLIFIER FUNCTION The LM48556 is a fully differential ceramic speaker driver that utilizes National’s inverting charge pump technology to deliver the high drive voltages required by ceramic speakers, without the need for noisy, board-space consuming inductive based regulators. The low-noise, inverting charge pump creates a negative supply (CPVSS) from the positive supply (PVDD). Because the amplifiers operate from these bipolar supplies, the maximum output voltage swing for each amplifier is doubled compared to a traditional single supply device. Additionally, the LM48556 is configured as a bridge-tied load (BTL) device, quadrupling the maximum theoretical output voltage range when compared to a single supply, single-ended output amplifier, see Bridged Configuration Explained section. The charge pump and BTL configuration allow the LM48556 to deliver over 17VP-P at 1kHz to a 1µF ceramic speaker while operating from a single 4.5V supply . Charge Pump Hold Capacitor (CSS) The value and ESR of the hold capacitor (CSS) directly affects the ripple on CPVSS. Increasing the value of CSS reduces output ripple. Decreasing the ESR of CSS reduces both output ripple and charge pump output impedance. A lower value capacitor can be used in systems with low maximum output power requirements. Gain Setting Resistor Selection The amplifier gain of the LM48556 is set by four external resistors, two per each input, RIN_ and RF_ (Figure 1). The amplifier gain is given by equation (1): DIFFERENTIAL AMPLIFIER EXPLANATION The LM48556 features a differential input stage, which offers improved noise rejection compared to a single-ended input amplifier. Because a differential input amplifier amplifies the difference between the two input signals, any component common to both signals is cancelled. An additional benefit of the differential input structure is the possible elimination of the DC input blocking capacitors. Since the DC component is common to both inputs, and thus cancelled by the amplifier, the LM48556 can be used without input coupling capacitors when configured with a differential input signal. AV = RF / RIN (V/V) (1) Careful matching of the resistor pairs, RF+ and RF-, and RIN+ and RIN-, is required for optimum performance. Any mismatch between the resistors results in a differential gain error that leads to an increase in THD+N, decrease in PSRR and CMRR, as well as an increase in output offset voltage. Resistors with a tolerance of 1% or better are recommended. The gain setting resistors should be placed as close to the device as possible. Keeping the input traces close together and of the same length increases noise rejection in noisy environments. Noise coupled onto the input traces which are physically close to each other will be common mode and easily rejected. BRIDGE CONFIGURATION EXPLAINED The LM48556 is designed to drive a load differentially, a configuration commonly referred to as a bridge-tied load (BTL). The BTL configuration differs from the single-ended configuration, where one side of the load is connected to ground. A BTL amplifier offers advantages over a single-ended device. Driving the load differentially doubles the output voltage compared to a single-ended amplifier under similar conditions. Any component common to both outputs is cancelled, thus there is no net DC voltage across the load, eliminating the DC blocking capacitors required by single-ended, single-supply amplifiers. Feedback Capacitor Selection Due to their capacitive nature, ceramic speakers poorly reproduce high frequency audio content. At high frequencies, a ceramic speaker presents a low impedance load to the amplifier, increasing the required drive current. The higher output current can drive the device into clipping, increasing THD+N. Low-pass filtering the audio signal improves audio quality by decreasing the signal amplitude at high frequencies, reducing the speaker drive current. Adding a capacitor in parallel with each feedback resistor creates a simple low-pass filter with the -3dB point determined by equation (2): SHUTDOWN FUNCTION The LM48556 features a low current shutdown mode. Set SD = GND to disable the amplifier and reduce supply current to 0.1µA. Switch SD between VDD and GND for minimum current consumption in shutdown. The LM48556 may be disabled with shutdown voltages less than 0.45V, however, the idle current will be greater than the typical 0.1µA value. f−3dB = 1 / 2πRFCF (Hz) PROPER SELECTION OF EXTERNAL COMPONENTS 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. Place a 4.7µF tantalum capacitor in parallel with a 0.1µF ceramic capacitor from VDD to GND. Additional bulk capacitance may be added as required. (2) Where RF is the value of the feedback resistor determined by equation (1) in the Gain Setting Resistors Selection section, and CF is the value of the feedback capacitor. The feedback capacitor is optional and not required for normal operation. Input Capacitor Selection 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 LM48556. The input capacitors create a high-pass filter with the input resistors RIN. The -3dB point of the high pass filter is found using Equation (3) below. Charge Pump Capacitor Selection Use low ESR ceramic capacitors (less than 100mΩ) for optimum performance. 11 www.national.com LM48556 Charge Pump Flying Capacitor (C1) The flying capacitor (C1) affects the load regulation and output impedance of the charge pump. A C1 value that is too low results in a loss of current drive, leading to a loss of amplifier headroom. A higher valued C1 improves load regulation and lowers charge pump output impedance to an extent. Above 4.7µF, the RDS(ON) of the charge pump switches and the ESR of C1 and CSS dominate the output impedance. A lower value capacitor can be used in systems with low maximum output power requirements. Application Information LM48556 f = 1 / 2πRINCIN (Hz) quencies, 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 1% or better are recommended for impedance matching and improved CMRR and PSRR. (3) Where the value of RIN is determined by equation (1) in the Gain Setting Resistor Selection section. When the LM48556 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 fre- SINGLE-ENDED AUDIO AMPLIFIER CONFIGURATION The LM48556 is compatible with single-ended sources. Figure 2 shows the typical single-ended applications circuit. In 30057286 FIGURE 2. Single-Ended Input Configuration www.national.com 12 Component Description LM48556TL LM48556TL Capacitor 4.7μF, ceramic, low ESR (<0.1Ω) 16V, -40°C to +85°C Capacitor Capacitor Capacitor Designator LM48556TL Footprint Quantity LM48556TL 1 C1 CR3216-1206 1 82μF, 16V, -40°C to +85°C CF+ CR2012-0805 1 82μF, 16V, -40°C to +85°C CF- CR2012-0805 1 0.47μF, 16V, -40°C to +85° CIN+ CR2012-0805 1 Capacitor 0.47μF, 16V, -40°C to +85°C CIN- CR2012-0805 1 Capacitor 4.7μF, 16V, -40°C to +85°C CS1 CR3216-1206 1 Capacitor 0.1μF ceramic, 16V, -40°C to +85°C CS2 CR2012-0805 1 Capacitor 10μF ceramic, low ESR (<0.1Ω) 16V, -40°C to +85°C CSS CR3216-1206 1 Header, 2–Pin Header 2 IN HDR1X2 1 Resistor 200kΩ RF+ CR2012-0805 1 Resistor 200kΩ RF+ CR2012-0805 1 Resistor 200kΩ RIN+ CR2012-0805 1 Resistor 200kΩ RIN- CR2012-0805 1 Header, 2–Pin Header 2 SPEAKER HDR1X2 1 Header, 2–Pin Header 2 VDD HDR1X2 1 Header, 3–Pin 3–pole jumper 3–pole jumper 1 J1 13 www.national.com LM48556 Bill Of Materials LM48556 Demonstration Board Schematic 300572b0 FIGURE 3: Demo Board Schematic www.national.com 14 LM48556 Demonstration Board PCB Views 300572b6 FIGURE 4: Top Overlay 300572b5 FIGURE 5: Top Layer 15 www.national.com LM48556 300572b3 FIGURE 6: Mid Layer 1 300572b4 FIGURE 7: Mid Layer 2 www.national.com 16 LM48556 300572b2 FIGURE 8: Bottom Overlay 300572b1 FIGURE 9: Bottom Layer 17 www.national.com LM48556 Revision History Rev Date 1.0 06/03/08 Initial release. 1.01 12/09/08 Changed Power Supply Voltage Limits from 4.5V to 5.0V. www.national.com Description 18 LM48556 Physical Dimensions inches (millimeters) unless otherwise noted 12 Bump micro SMD Order Number LM48556TL, LM48556TLX NS Package Number TLA121AA X1 = 1488μm, X2 = 1996μm, X3 = 600μm 19 www.national.com LM48556 Fully Differential, Mono, Ceramic Speaker Driver 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® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage Reference www.national.com/vref Design Made Easy www.national.com/easy PowerWise® Solutions www.national.com/powerwise Solutions www.national.com/solutions Serial Digital Interface (SDI) www.national.com/sdi Mil/Aero www.national.com/milaero Temperature Sensors www.national.com/tempsensors Solar Magic® www.national.com/solarmagic Wireless (PLL/VCO) www.national.com/wireless Analog University® www.national.com/AU THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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