Production Data
WM8750JL
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.
REGISTER
ADDRESS
BIT
LABEL
LINSEL
DEFAULT
DESCRIPTION
R32 (20h)
00
Left Channel Input Select
00 = LINPUT1
7:6
ADC Signal
Path Control
(Left)
01 = LINPUT2
10 = LINPUT3
11 = L-R Differential (either LINPUT1-
RINPUT1 or LINPUT2-RINPUT2,
selected by DS)
LMICBOOST
RINSEL
00
00
Left Channel Microphone Gain Boost
00 = Boost off (bypassed)
01 = 13dB boost
5:4
7:6
10 = 20dB boost
11 = 29dB boost
R33 (21h)
Right Channel Input Select
00 = RINPUT1
ADC Signal
Path Control
(Right)
01 = RINPUT2
10 = RINPUT3
11 = L-R Differential (either LINPUT1-
RINPUT1 or LINPUT2-RINPUT2,
selected by DS)
RMICBOOST
00
Right Channel Microphone Gain Boost
00 = Boost off (bypassed)
01 = 13dB boost
5:4
10 = 20dB boost
11 = 29dB boost
Table 3 Input Software Control
REGISTER
ADDRESS
BIT
LABEL
RDCM
DEFAULT
DESCRIPTION
R31 (1Fh)
ADC input Mode
0
Right Channel DC Measurement
0 = Normal Operation, PGA Enabled
1 = Measure DC level on RINPUT1
Left Channel DC Measurement
5
LDCM
0
4
0 = Normal Operation, PGA Enabled
1 = Measure DC level on LINPUT1
Table 4 DC Measurement Select
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R31 (1Fh)
ADC Input Mode
DS
0
Differential input select
0: LINPUT1 – RINPUT1
1: LINPUT2 – RINPUT2
8
Table 5 Differential Input Select
PD, April 2012, Rev 4.1
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