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3. Technical Brief
3.15.2.2 MAX9877 audio interface
The MAX9877 combines a high-efficiency Class D audio power amplifier with a stereo Class AB
capacitorless DirectDrive® headphone amplifier. Maxim’s 3rd
generation, filterless Class D amplifier with active emissions limiting technology provides Class AB
performance with Class D efficiency.
The MAX9877 delivers up to 725mW from a 3.7V supply into an 8 load with 87% efficiency to extend
battery life. The filterless modulation scheme combined with active
emissions limiting circuitry and spread-spectrum modulation greatly reduces EMI while eliminating the
need for output filtering used in traditional Class D devices.
The stereo Class AB headphone amplifier in the MAX9877 uses Maxim’s patented DirectDrive architecture,
that produces a ground-referenced output from a single supply, eliminating the need for large DC-
blocking capacitors, saving cost, space, and component height.
The device utilizes a user-defined input architecture, three preamplifier gain settings, an input mixer,
volume control, comprehensive click-and-pop suppression, and I2C control. A bypass mode feature
disables the integrated Class D amplifier and utilizes an internal DPST switch to allow an external amplifier
to drive the speaker that is connected at the outputs of the MAX9877.
The MAX9877 is available in a thermally efficient, space-saving 20-bump WLP package.
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