Production Data
WM9715L
RECORD GAIN
The amplitude of the signal that enters the audio ADC is controlled by the Record PGA
(Programmable Gain Amplifier). The PGA gain can be programmed either by writing to the Record
Gain register, or by the Automatic Level Control (ALC) circuit (see next section). When the ALC is
enabled, any writes to the Record Gain register have no effect.
Two different gain ranges can be implemented: the standard gain range defined in the AC’97
standard, or an extended gain range with smaller gain steps. The ALC circuit always uses the
extended gain range, as this has been found to result in better sound quality.
The output of the Record PGA can also be mixed into the phone and/or headphone outputs (see
“Audio Mixers”). This makes it possible to use the ALC function for the microphone signal in a
smartphone application.
REGISTER
ADDRESS
BIT
15
LABEL
RMU
DEFAULT
DESCRIPTION
1Ch
1
Mute Audio ADC (both channels)
1: Mute (OFF)
Record Gain
0: No Mute (ON)
14
GRL
0
Gain range select (left)
0: Standard (0 to 22.5dB, 1.5dB step size)
1: Extended (-17.25 to +30dB, 0.75dB steps)
Record Volume (left)
13:8
RECVOLL
000000
Standard (GRL=0)
XX0000: 0dB
Extended (GRL=1)
000000: -17.25dB
000001: -16.5dB
… (0.75dB steps)
111111: +30dB
XX0001: +1.5dB
… (1.5dB steps)
XX1111: +22.5dB
Zero Cross Enable
7
ZC
0
0
0: Record Gain changes immediately
1: Record Gain changes when signal is zero
or after time-out
6
GRR
Gain range select (right)
Similar to GRL
5:0
RECVOLR 000000
Record Volume (right)
Similar to RECVOLL
Table 8 Record Gain Register
PD Rev 4.0 December 2007
21
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
