Production Data
WM8737L
Note: The 3D enhancement function is not supported at sample frequencies of 88.2kHz, 88.235kHz,
and 96kHz. When using these sample frequencies the 3D enhancement function should be bypassed
by first setting register R13 (0Dh) to 1_110x_xxxx (1C0h), where x_xxxx represents the required
values for the ALC in the application, and then setting register R28 (1Ch) to 0_0000_0100 (004h).
Note that the above sequence uses test bits that are not documented and the use of these test bits,
other than as described above, is not recommended and is not supported.
REGISTER
ADDRESS
BIT
LABEL
3DEN
DEFAULT
DESCRIPTION
3D function enable
R4 (04h)
0
0
3D Control
0: disable
1: enable
4:1
3DDEPTH[3:0]
0000
Stereo depth
0000: 0% (minimum 3D effect)
0001: 6.67%
....
1110: 93.3%
1111: 100% (maximum 3D effect)
Upper Cut-off frequency
0 = High (2.2kHz at 48kHz sampling)
1 = Low (1.5kHz at 48kHz sampling)
Lower Cut-off frequency
0 = Low (200Hz at 48kHz sampling)
1 = High (500Hz at 48kHz sampling)
ADC 6dB attenuate enable
0: disabled (0dB)
5
6
7
3DUC
3DLC
DIV2
0
0
0
1: -6dB enabled
Table 11 Stereo Enhancement Control
AUTOMATIC LEVEL CONTROL (ALC)
The WM8737L has an automatic level control that aims to keep a constant recording volume
irrespective of the input signal level. This is achieved by continuously adjusting the PGA gain so that
the signal level at the ADC input remains constant. A digital peak detector monitors the ADC output
and changes the PGA gain if necessary.
input
signal
PGA
gain
signal
after
ALC
ALC
target
level
hold decay
time time
attack
time
Figure 8 ALC Operation
PD, Rev 4.4, January 2012
21
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