WM8941
Pre Production
RECOMMENDED VIDEO BUFFER INITIALISATION SEQUENCE
Power Up (Video signal AC coupled to Video Buffer input):
1.
2.
3.
4.
5.
6.
7.
8.
9.
Turn on external power supplies. Wait for supply voltages to settle.
Reset internal registers to default state (software reset).
Set VMIDSEL[1:0] bits for 50kΩ reference string impedance. *Note 1.
Enable bias (BIASEN=1) and Level Shift circuits (LVLSHIFT_EN=1).
Set Video Buffer Gain (VBGAIN) as required.
Set Video Buffer Filter Q Boost (QBOOST) as required.
Enable Video Buffer Clamp (VBCLAMPEN=1).
Enable Video Buffer Pulldown to High Impedance (VBPULLDWN=1).
Enable video buffer (VBUFEN=1).
10.
11.
Wait for 1.5seconds.
Disable Video Buffer Pulldown (VBPULLDWN=0).
Power Up (Video signal DC coupled to Video Buffer input):
1.
2.
3.
4.
5.
6.
7.
Turn on external power supplies. Wait for supply voltages to settle.
Reset internal registers to default state (software reset).
Set VMIDSEL[1:0] bits for 50kΩ reference string impedance. *Note 1.
Enable bias (BIASEN=1) and Level Shift circuits (LVLSHIFT_EN=1).
Set Video Buffer Gain (VBGAIN) as required.
Set Video Buffer Filter Q Boost (QBOOST) as required.
Enable video buffer (VBUFEN=1).
Notes:
1. Choose the value of VMIDSEL bits based on the startup time (VMIDSEL = 10 for the slowest
startup, VMIDSEL = 11 for the fastest startup). Startup time is defined by the value of the
VMIDSEL bits (the reference impedance) and the external decoupling capacitor on VMID.
PP, Rev 3.3, December 2007
56
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
