wm8351 Wolfson Microelectronics plc, wm8351 Datasheet - Page 64

• Manufacturer Part Number: wm8351
• Description: Wolfson Audioplus? Stereo Codec With Power Management
• Manufacturer: Wolfson Microelectronics plc

WM8351
13.4 INPUT SIGNAL PATH
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The WM8351 has multiple analogue inputs. There are two input channels, Left and Right, each of
which consists of an input PGA stage followed by a boost/mix stage switch into the hi-fi ADC. Each
input PGA path has three input pins which can be configured in a variety of ways to accommodate
single-ended, differential or dual differential microphones. There are two auxiliary input pins which
can be fed into to the input boost/mix stage as well as driving into the output path. A bypass path
exists from the output of the boost/mix stage into the output left/right mixers.
13.4.1
The microphone inputs of the WM8351 are designed to accommodate electret condenser
microphones or analogue line-in signals. They comprise the following pins:
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•
•
•
•
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The non-inverting inputs have constant input impedance to VMID, whereas the inverting input’s
impedance varies with the pre-amplifier’s gain. (Note: the terms “inverting” and “non-inverting” refer
to the microphone pre-amplifiers only. For overall behaviour, the inverting record mixer and the ADC,
whose output can optionally be inverted in the digital domain, must also be taken into account.)
Each
pseudo-differentially connected microphones. The amplified signal for each channel can be digitised
in the audio ADC and/or mixed into the output signal path.
Figure 37 Microphone Inputs and Pre-amplifiers
IN1LP: first non-inverting input, left channel
IN2L: second non-inverting input, left channel
IN1LN: inverting input, left channel
IN1RP: first non-inverting input, right channel
IN2R: second non-inverting input, right channel
IN1RN: inverting input, right channel
channel
MICROPHONE INPUTS
has
a
programmable
pre-amplifier,
which
supports
PD, June 2009, Rev 4.1
single-ended
Production Data
64
or