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
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 filters.
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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