The LM48511 device integrates a boost converter with a
high-efficiency Class D audio power amplifier to provide 3-W continuous power into an 8-Ω speaker
when operating from a 5-V power supply.
When operating from a 3-V to 4-V power supply, the LM48511 can be
configured to drive 1 to 2.5 W into an 8-Ω load with less than 1% distortion (THD+N). The Class D
amplifier features a low-noise PWM architecture that eliminates the output filter, reducing
external component count, board area consumption, system cost, and simplifying design. A selectable
spread spectrum modulation scheme suppresses RF emissions, further reducing the need for output
The switching regulator of the LM48511 is a current-mode boost
converter operating at a fixed frequency of 1 MHz. Two selectable feedback networks allow the
LM48511 regulator to dynamically switch between two different output voltages,
improving efficiency by optimizing the amplifier’s 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 5 V, extends battery life when compared
to Boosted 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 overload protection prevent the device from damage during fault conditions. Superior click
and pop suppression eliminates audible transients during power-up and shutdown.
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