Document
LM48520 Boosted Stereo Class D Audio Power Amplifier with Output Speaker Protection and Spread Spectrum
March 20, 2008
LM48520 Boosted Stereo Class D Audio Power Amplifier with Output Speaker Protection and Spread Spectrum
General Description
The LM48520 integrates a boost converter with a high efficiency Class D stereo audio power amplifier to provide up to 1W/ch continuous power into an 8Ω speaker when operating from 2.7V to 5.0V power supply with boost voltage (PV1) of 5.0V. The LM48520 utilizes a proprietary spread spectrum pulse width modulation technique that lowers RF interference and EMI levels. The Class D amplifier is a low noise, filterless PWM architecture that eliminates the output filter, reducing external component count, board area, power consumption, system cost, and simplifying design. The LM48520 is designed for use in mobile phones and other portable communication devices. The high (78%) efficiency extends battery life when compared to Boosted Class AB amplifiers. The LM48520 features a low-power consumption shutdown mode. Shutdown may be enabled by driving the Shutdown pin to a logic low (GND). Also, external leakage is minimized via control of the ground reference via the SWOUT pin . The LM48520 has 4 gain options which are pin selectable via Gain0 and Gain1 pins. Output short circuit prevents the device from damage during fault conditions. Superior click and pop suppression eliminates audible transients during powerup and shutdown.
Key Specifications
■ Quiescent Power Supply Current ■ Output Power
(RL = 8Ω, THD+N ≤ 1%, VDD = 3.3V,PV1 = 5.0V) 11.5mA (typ)
1.1W (typ) 0.04μA (typ)
■ Shutdown Current
Features
■ ■ ■ ■ ■ ■ ■ ■ ■ ■
Click and Pop Suppression Low 0.04μA Shutdown Current 78% Efficiency Filterless Class D 2.7V - 5.0V operation 4 Adjustable Gain settings Adjustable output swing limiter with Soft Clipping Speaker Protection Short circuit protection on Audio Amps Independent Boost and Amplifier shutdown pins
Applications
■ ■ ■ ■ ■
Mobile Phones PDAs Portable media Cameras Handheld games
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2008 National Semiconductor Corporation
201987
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LM48520
Typical Application
20198701
FIGURE 1. Typical LM48520 Audio Amplifier Application Circuit
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LM48520
Connection Diagrams
LM48520TL
20198702
Top View Order Number LM48520TL See NS Package Number TLA25AAA
Micro SMD Marking
20198721
Top View X — Date Code T — Die Traceability G — Boomer Family I5 — LM48520TL
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LM48520
Pin Descriptions
Pin Designator A1 A2 A3 A4 A5 B1 B2 B3 B4 B5 C1 C2 C3 C4 C5 D1 D2 D3 D4 D5 E1 E2 E3 E4 E5 Pin Name VDD BstFB Soft Start SW_GND SW INR+ INRFB_GND INLINL+ V1 BstSD GND Gain0 PV1 AmpSD OUTR+ NC OUTL+ Gain1 VLimit OUTRPGND OUTLNC Power Supply Regulator Feedback Input. Connect BstFB to an external resistive voltage divider to set the boost output voltage. Soft start capacitor Booster ground Drain of the Internal FET switch Non-inverting right channel input Inverting right channel input Ground return for R1, R2 resistor divider Inverting left channel input Non-inverting left channel input Amplifier supply voltage. Connect to PV1. Regulator active low shutdown Ground Gain setting input 0 Amplifier H-bridge power supply. Connect to V1. Amplifier active low shutdown Non-inverting right channel output No connect Non-inverting left channel output Gain setting input 1 Set to control output clipping level Inverting right channel output Power ground Inverting left channel output No connect Pin Function
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LM48520
Absolute Maximum Ratings (Note 2)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (VDD, V1) Storage Temperature Input Voltage Power Dissipation (Note 3) ESD Susceptibility (Note 4) ESD Susceptibility (Note 5) Junction Temperature 6V −65°C to +150°C −0.3V to VDD + 0.3V Internally limited 2000V 200V 150°C
Thermal Resistance θJA (TL) 40.5 °C/W
Operating Ratings
Temperature Range TMIN ≤ TA ≤ TMAX Supply Voltage (VDD) Amplifier Voltage (V1 ) Not under Boosted Condition Amplifier Voltage (PV1 ) Under Boosted Condition (Notes 1, 2) −40°C ≤ TA ≤ +85°C 2.7V ≤ VDD ≤ 5.0V 2.4V ≤ V1 ≤ 5.5V 3.0V ≤ PV1 ≤ 5.0V
Electrical Characteristics VDD = 3.3V
Symbol Parameter
The following specifications apply for VDD = 3.3V, AV = 6dB, RL = 15µH + 8Ω +15µH, fIN = 1kHz, unless otherwise specified. Limits apply for TA = 25°C, R1 = 40.2kΩ, R2 = 16.2kΩ, V1 = PV1 = 5V, Vlimit = GND. All electrical specifications are for amplifier and booster. Conditions LM48520 Typical (Note 6) VIN = 0, RLOAD = ∞ IDD Quiescent Power Supply Current VDD = 2.7V VDD = 3.3V VDD = 5.0V ISD VSDIH VSDIL TWU VOS Shutdown Current Shutdown Voltage Input High Shutdown Voltage Input Low Wake-up Time Output Offset.