Rainbow Electronics MAX9860 - Manual (Page 14)

MAX9860
Detailed Description
The MAX9860 is a low-power, voiceband, mono audio
codec designed to provide a complete audio solution
for wireless voice headsets and other mono audio
devices.
The mono playback path accepts digital audio over a
flexible digital audio interface compatible with I
2 S, TDM,
and left-justified audio signals. An oversampling sigma-
delta DAC converts an incoming digital data stream to
analog audio and outputs through the mono bridge-tied
load headphone amplifier.
The stereo record path has two microphone inputs with
selectable gain. The microphones are powered by an
integrated microphone bias. An oversampling sigma-
delta ADC converts the microphone signals and out-
puts the digital bit stream over the digital audio
interface.
The record path includes automatic gain control (AGC)
to optimize the signal level and a noise gate to reduce
idle noise. The automatic gain control monitors the out-
puts of the ADC and makes constant adjustments to the
input gain to reduce the dynamic range of the incoming
microphone signal by up to 20dB. The noise gate cor-
rects for the increase in noise typically associated with
AGC by lowering the gain when there is no audio signal.
Integrated digital filtering provides a range of notch and
highpass filters for both the playback and record paths
to limit undesirable low-frequency signals and GSM
transmission noise. The digital filtering provides attenu-
ation of out-of-band energy by up to 76dB, eliminating
audible aliasing. A digital sidetone function allows
audio from the record path to be summed into the play-
back path after digital filtering.
The MAX9860’s flexible clock circuitry utilizes a pro-
grammable clock divider and a digital PLL to allow the
DAC and ADC to operate at maximum dynamic range
for all combinations of master clock (MCLK) and sam-
ple rate (LRCLK). Any master clock between 10MHz to
60MHz is supported as are all sample rates from 8kHz
to 48kHz. Master and slave mode are supported for
maximum flexibility.
I 2 C Registers
The MAX9860 audio codec is completely controlled
through software using an I
2 C interface. The power-on
default setting is software shutdown, requiring that the
internal registers be programmed to activate the device.
See Table 1 for the device’s complete register map.
I 2 C Slave Address
The MAX9860 responds to the slave address 0x20 for
all write commands and 0x21 for all read operations.
16-Bit Mono Audio Voice Codec
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