wm8988 Wolfson Microelectronics plc, wm8988 Datasheet - Page 17

• Manufacturer Part Number: wm8988
• Description: Stereo Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

Production Data
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The signal inputs are biased internally to the reference voltage VREF. Whenever the line inputs are
muted or the device placed into standby mode, the inputs are kept biased to VREF using special
anti-thump circuitry. This reduces any audible clicks that may otherwise be heard when changing
inputs.
DC MEASUREMENT
For DC measurements (for example, battery voltage monitoring), the input signal at the LINPUT1
and/or RINPUT1 pins can be taken directly into the respective ADC, bypassing both PGA and
microphone boost. The ADC output then becomes unsigned relative to AVDD, instead of being a
signed (two’s complement) number relative to VREF. Setting L/RDCM will override L/RINSEL. The
input range for dc measurement is AGND to AVDD.
Table 4 Input Software Control
Table 5 DC Measurement Select
Table 6 Differential Input Select
R32 (20h)
ADC Signal
Path Control
(Left)
R33 (21h)
ADC Signal
Path Control
(Right)
R31 (1Fh)
ADC input Mode
R31 (1Fh)
ADC Input Mode
REGISTER
REGISTER
REGISTER
ADDRESS
ADDRESS
ADDRESS
7:6
5:4
7:6
5:4
BIT
BIT
BIT
5
4
8
LINSEL
LMICBOOST
RINSEL
RMICBOOST
RDCM
LDCM
DS
LABEL
LABEL
LABEL
00
00
00
00
0
0
0
DEFAULT
DEFAULT
DEFAULT
Left Channel Input Select
00 = LINPUT1
01 = LINPUT2
10 = Reserved
11 = L-R Differential (either LINPUT1-
Left Channel Microphone Gain Boost
00 = Boost off (bypassed)
01 = 13dB boost
10 = 20dB boost
11 = 29dB boost
Right Channel Input Select
00 = RINPUT1
01 = RINPUT2
10 = Reserved
11 = L-R Differential (either LINPUT1-
00 = Boost off (bypassed)
01 = 13dB boost
10 = 20dB boost
11 = 29dB boost
Right Channel DC Measurement
0 = Normal Operation, PGA Enabled
1 = Measure DC level on RINPUT1
Left Channel DC Measurement
0 = Normal Operation, PGA Enabled
1 = Measure DC level on LINPUT1
0: LINPUT1 – RINPUT1
1: LINPUT2 – RINPUT2
Right Channel Microphone Gain Boost
Differential input select
RINPUT1 or LINPUT2-RINPUT2,
selected by DS)
RINPUT1 or LINPUT2-RINPUT2,
selected by DS)
DESCRIPTION
DESCRIPTION
DESCRIPTION
PD, Rev 4.0, October 2008
WM8988
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