MAX9888 Maxim Integrated Products, MAX9888 Datasheet - Page 60

• Manufacturer Part Number: MAX9888
• Description: Stereo Audio CODEC
• Manufacturer: Maxim Integrated Products

DataSheet.in
Stereo Audio CODEC
with FLEXSOUND Technology
The device includes three differential microphone inputs
and a low-noise microphone bias for powering the micro-
phones (Figure 6). One microphone input can also be con-
figured as a digital microphone input accepting signals
from up to two digital microphones. Two microphones,
analog or digital, can be recorded simultaneously.
In the typical application, one microphone input is used
for the handset microphone and the other is used as an
accessory microphone. In systems using a background
noise microphone, INA can be retasked as another
microphone input.
In systems where the codec is not the only device
recording microphone signals, connect microphones to
60
Figure 6. Microphone Input Block Diagram
MICBIAS
MIC1P/
DIGMICDATA
MIC1N/
DIGMICCLK
MIC2P
MIC2N
INA1/EXTMICP
INA2/EXTMICN
MIC2BYP
MBEN
INABYP
REG
Microphone Inputs
MCLK
CONTROL
CLOCK
EXTMIC
EXTMIC
PSCLK
PA1EN:
0/20/30dB
PA2EN:
0/20/30dB
PGAINA:
+20dB TO -6dB
PGAINA:
+20dB TO -6dB
MIC2P/MIC2N and EXTMICP/EXTMICN. MIC1P/MIC1N
then become outputs that route the microphone signals
to an external device as needed. Two devices can then
record microphone signals without needing external
analog switches.
Analog microphone signals are amplified by two stages
of gain and then routed to the ADCs. The first stage offers
selectable 0dB, 20dB, or 30dB settings. The second
stage is a programmable-gain amplifier (PGA) adjustable
from 0dB to 20dB in 1dB steps. To maximize the signal-
to-noise ratio, use the gain in the first stage whenever
possible. Zero-crossing detection is included on the PGA
to minimize zipper noise while making gain changes.
PGAM1:
+20dB TO 0dB
PGAM1:
+20dB TO 0dB
INADIFF
MIXADR
MIXADL
MIX
MIX
ADREN
ADLEN
ADCL
ADCR