wm8350 Wolfson Microelectronics plc, wm8350 Datasheet - Page 63

• Manufacturer Part Number: wm8350
• Description: Wolfson Audioplus? Stereo Codec With Power Management
• Manufacturer: Wolfson Microelectronics plc

Production Data
13.4 INPUT SIGNAL PATH
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Power Down:
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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
The microphone inputs of the WM8350 are designed to accommodate electret condenser
microphones or analogue line-in signals. They comprise the following pins:
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.
Mute all outputs
Enable anti-pop circuits by setting ANTI_POP = 01.
Disable circuits down-stream on outputs
Disable VMID by setting VMID_ENA = 0.
Wait for VMID to discharge (typically 500ms)
Disable the anti-pop circuits by setting ANTI_POP = 00.
Disable all outputs
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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
MICROPHONE INPUTS
PD, June 2009, Rev 4.1
WM8350
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