The MAX9851/MAX9853 are single-chip, stereo audio
CODECs designed to provide a complete audio solution
for a GSM/GPRS/EDGE cell phone. The MAX9851/MAX9853 provide stereo DirectDrive™ headphone amplifiers, a mono receiver speaker amplifier, stereo Class D speaker amplifiers (MAX9851 only), stereo differential
line outputs (MAX9853 only), microphone input
amplifiers, plus flexible input selection and gain control.
Two serial digital audio interfaces are included, one
intended to accept voiceband data and the other
accepting I²S data. The voiceband interface can be
reconfigured as needed to act as a secondary I²S feed
input—allowing multiple audio source mixing of ringer
tones or other audio at different sample rates. A transducer/vibrator signal can be derived from digital audio.
The stereo digital-to-analog converter (DAC) path
includes filtering and mixing, programmable-gain amplifiers
(PGA), soft muting, and optional voiceband digital
filtering. The MAX9851/MAX9853 accept up to two digital
audio inputs at different sample rates. All analog inputs
have PGAs on the front end, allowing dynamic range
optimization with a wide range of input sources.
The stereo analog-to-digital converter (ADC) converts
audio signals from either internal or external microphones
or stereo line inputs. The microphone amplifiers have a
programmable gain from 0 to 40dB to handle both amplified
microphones and electret modules. In addition to a
digital highpass filter to remove DC offset voltages, the
ADC also features voiceband digital filtering.
The digital audio interfaces support a variety of serial
audio formats. The secondary serial audio interface has
an independent supply voltage to allow integration into
multiple supply systems. Control for volume levels, signal
mixing, and operating modes is done through the
I²C 2-wire interface.
All circuitry is optimized for high PSRR. The MAX9851/MAX9853 use a thermally efficient, space-saving 48-pin thin QFN package (7mm x 7mm x 0.8mm) with an
exposed pad.
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