3w, Ultra-low Emi, Filterless, Mono, Class D Audio Power Amplifier With Spread Spectrum - National Semiconductor

The LM48511 integrates a boost converter with a high effi- ciency Class D Audio Power Amplifier to provide 3W continu- ous power into an 8 speaker when operating from a 5V power supply. When operating from a 3V to 4V power supply, the LM48511 CAN be configured to drive 1 to 2.5W into an 8 load with less than 1% distortion (THD+N). The Class D Amplifier features a low noise PWM architecture that elimi- nates the output Filter reducing external component count, board area consumption, system cost, and simplifying design. A selectable spread spectrum modulation scheme suppress- es RF emissions, further reducing the need for output Filters The LM48511s Switching Regulator is a current-mode boost converter operating at a fixed frequency of 1MHz. Two se- lectable feedback networks allow the LM48511 Regulator to dynamically Switch between two different output voltages, im- proving efficiency by optimizing the Amplifiers supply voltage based on battery voltage and output power requirements. The LM48511 is designed for use in portable devices, such as GPs mobile phones, and MP3 players. The high, 80% efficiency at 5V, extends battery life when compared to Boost- ed Class AB Amplifiers Independent Regulator and Amplifier shutdown controls optimize power savings by disabling the Regulator when high output power is not required. The gain of the LM48511 is set by external resistors, which allows independent gain control from multiple sources by summing the signals. Output short circuit and thermal over- load protection prevent the device from damage during fault conditions. Superior click and pop suppression eliminates au- dible transients during power-up and shutdown. By National Semiconductor Corporation