WM8350 Datasheet, PDF (63/340 Pages) Wolfson Microelectronics plc – Wolfson AudioPlus™ Stereo CODEC with Power Management

Production Data
Power Down:
1. Mute all outputs
2. Enable anti-pop circuits by setting ANTI_POP = 01.
3. Disable circuits down-stream on outputs
4. Disable VMID by setting VMID_ENA = 0.
5. Wait for VMID to discharge (typically 500ms)
6. Disable the anti-pop circuits by setting ANTI_POP = 00.
7. Disable all outputs
WM8350
13.4 INPUT SIGNAL PATH
The WM8350 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 WM8350 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.
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PD, February 2011, Rev 4.4
63