WM8352
Production Data
13.4 INPUT SIGNAL PATH
The WM8352 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 MICROPHONE INPUTS
The microphone inputs of the WM8352 are designed to accommodate electret condenser
microphones or analogue line-in signals. They comprise the following pins:
.
.
.
.
.
.
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
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 channel has
a
programmable pre-amplifier, which supports single-ended or
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
PD, February 2011, Rev 4.4
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
