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MAX9880A View Datasheet(PDF) - Maxim Integrated

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MAX9880A Datasheet PDF : 70 Pages
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Low-Power, High-Performance
Dual I2S Stereo Audio Codec
Table 16. Microphone Input Registers (continued)
BITS
PGAML/
PGAMR
FUNCTION
Left/Right Microphone Programmable Gain Amplifier
SETTING
GAIN (dB)
SETTING
0x00
+20
0x0B
0x01
+19
0x0C
0x02
+18
0x0D
0x03
+17
0x0E
0x04
+16
0x0F
0x05
+15
0x10
0x06
+14
0x11
0x07
+13
0x12
0x08
+12
0x13
0x09
+11
0x14 to 0x1F
0x0A
+10
GAIN (dB)
+9
+8
+7
+6
+5
+4
+3
+2
+1
0
ADC
The MAX9880A includes two 18-bit ADCs. The first
ADC is used to record left-channel microphone and
line-input audio signals. The second ADC can be used
to record right-channel microphone and line-input sig-
nals or it can be configured to accurately measure DC
voltages.
When measuring DC voltages both the left and right ADC
must be enabled by setting ADLEN and ADREN in regis-
ter 0x26. The input to the second ADC is JACKSNS/
AUX and the output is reported in AUX (registers 0x02
and 0x03). Since the audio ADC is used to perform the
measurement, the digital audio interface must be prop-
erly configured. If the left ADC is being used to convert
audio, then the DC measurement is performed at the
same sample rate. When not using the left ADC, config-
ure the digital interface for a 48kHz sample rate to
ensure the fastest possible settling time.
To ensure accurate results, the MAX9880A includes
two calibration routines. Calibrate the ADC each time
the MAX9880A is powered on. Calibration settings are
not lost if the MAX9880A is placed in shutdown. When
making a measurement, set AUXCAP to 1 to prevent
AUX from changing while reading the registers.
Setup Procedure
1) Ensure a valid MCLK signal is provided and config-
ure PSCLK appropriately.
2) Choose a clocking mode. The following options are
possible:
a. Slave mode with LRCLK and BCLK signals
provided. The measurement sample rate is
determined by the external clocks.
b. Slave mode with no LRCLK and BCLK signals
provided. Configure the device for normal clock
mode using the NI ratio. Select fS = 48kHz to
allow for the fastest settling times.
c. Master mode with audio. Configure the device
in normal mode using the NI ratio or exact inte-
ger mode using FREQ1 as required by the audio
signal.
d. Master mode without audio. Configure the
device in normal mode using the NI ratio. Select
fS = 48kHz to allow for the fastest settling times.
3) Ensure jack sense is disabled.
4) Enable the left and right ADC; take the MAX9880A
out of shutdown.
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