LM48511 - 3W, Ultra Low EMI, Mono Class D Audio Amplifier with Spread Spectrum

The LM48511 device integrates a boost converter with ahigh-efficiency Class D audio power amplifier to provide 3-W continuous power into an 8-Ω speakerwhen operating from a 5-V power supply.

When operating from a 3-V to 4-V power supply, the LM48511 can beconfigured to drive 1 to 2.5 W into an 8-Ω load with less than 1% distortion (THD+N). The Class Damplifier features a low-noise PWM architecture that eliminates the output filter, reducingexternal component count, board area consumption, system cost, and simplifying design. A selectablespread spectrum modulation scheme suppresses RF emissions, further reducing the need for outputfilters.

The switching regulator of the LM48511 is a current-mode boostconverter operating at a fixed frequency of 1 MHz. Two selectable feedback networks allow theLM48511 regulator to dynamically switch between two different output voltages,improving efficiency by optimizing the amplifier’s supply voltage based on battery voltage andoutput power requirements.

The LM48511 is designed for use in portable devices, such as GPS,mobile phones, and MP3 players. The high, 80% efficiency at 5 V, extends battery life when comparedto Boosted Class AB amplifiers. Independent regulator and amplifier shutdown controls optimizepower savings by disabling the regulator when high-output power is not required.

The gain of the LM48511 is set by external resistors, which allowsindependent gain control from multiple sources by summing the signals. Output short circuit andthermal overload protection prevent the device from damage during fault conditions. Superior clickand pop suppression eliminates audible transients during power-up and shutdown.

• 3-W Output into 8 Ω at 5 V With THD+N = 1%
• Selectable Spread Spectrum Mode Reduces EMI
• 80% Efficiency
• Independent Regulator and Amplifier Shutdown Controls
• Dynamically Selectable Regulator Output Voltages
• Filterless Class D
• 3-V to 5.5-V Operation
• Low Shutdown Current
• Click and Pop Suppression
• Key Specifications
  • Quiescent Power Supply Current
    • V_DD = 3 V 9 mA (Typical)
    • V_DD = 5 V 13.5 mA (Typical)
  • P_O at V_DD = 5 V, PV1 = 7.8 V, R_L = 8 Ω,
    THD+N = 1% 3 W (Typical)
  • P_O at V_DD = 3 V, PV1 = 4.8 V, R_L = 8 Ω,
    THD+N = 1% 1 W (Typical)
  • P_O at V_DD = 5 V, PV1 = 7.8 V, R_L = 4 Ω,
    THD+N = 1% 5.4 W (Typical)
  • Shutdown Current at V_DD = 3 V, 0.01 µA (Typical)

All trademarks are the property of their respective owners.