Pre Production
WM8941
POP MINIMISATION
Power-On-Bias Control (POB_CTRL) selects the bias current source for the output stages of the
WM8941. 0 selects the VMID derived bias source (normal operation), 1 selects a non-VMID derived
source which allows the output amplifiers to be enabled before VMID at start-up. This feature can be
used to minimise pops. Once VMID is enabled and has stabilised, POBCTRL should be set to 0.
Register SOFT_START is the enable bit for the VMID soft-start function. Setting the bit to 1 causes
charging of the VMID decoupling cap to follow a soft-start profile which minimises pops. This soft-
start profile has minimal impact on VMID charge time.
Fast VMID discharge is enabled using TOGGLE. Setting to 1 opens a low impedance discharge path
from VMID to GND. This function can be used during power down to reduce the discharge time of
the VMID decoupling cap. Must be set to 0 for normal operation.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
Power on Bias Control
R7
Additional Control
6
5
4
POB_CT
RL
0
0=normal (current bias based on VMID)
1=Startup (current bias not based on VMID)
VMID Soft Start
SOFT_ST
ART
0
0
0=disabled
1=enabled
TOGGLE
Fast VMID Discharge
0=normal
1=enable (used during power-down)
Table 61 POP Minimisation Control
PP, Rev 3.3, December 2007
75
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
