WM8961
Pre-Production
REGISTER
ADDRESS
BIT
LABEL
OUT1VU
DEFAULT
DESCRIPTION
R2 (02h)
LOUT1
Volume
8
0
Headphone Volume Update
0 = Store LOUT1VOL in intermediate
latch (no gain change)
1 = Update left and right channel gains
(left = LOUT1VOL, right = intermediate
latch)
7
LO1ZC
0
Left zero cross enable
0 = Change gain immediately
1 = Change gain on zero cross only
6:0
LOUT1VOL
[6:0]
0000000
(MUTE)
LOUT1 Volume
1111111 = +6dB
… 1dB steps down to
0110000 = -73dB
0101111 to 0000000 = Analogue
MUTE
R3 (03h)
ROUT1
Volume
8
7
OUT1VU
RO1ZC
0
0
Headphone Volume Update
0 = Store ROUT1VOL in intermediate
latch (no gain change)
1 = Update left and right channel gains
(left = intermediate latch, right =
ROUT1VOL)
Right zero cross enable
0 = Change gain immediately
1 = Change gain on zero cross only
6:0
6
ROUT1VOL
[6:0]
0000000
(MUTE)
ROUT1 Volume
Similar to LOUT1VOL
R26 (1Ah)
Power
LOUT1_PGA
0
LOUT1 left headphone PGA Output
Enable
Management
(2)
5
ROUT1_PGA
0
ROUT1 right headphone PGA Output
Enable
Table 28 Headphone Output PGA Volume Control
See "Volume Updates" section for a description of the volume update function, the zero cross function
and the timeout operation.
HEADPHONE OUTPUT DRIVE STAGE
The headphone output drive stage is a stereo differential to single-ended amplifier. It is capable of
driving 16Ω or 32Ω headphones without the need for large AC coupling capacitors, which is achieved
by having separate positive and negative supplies, generated by a charge pump, detailed in the
“Charge Pump” section. It also permits power up and power down with minimised ‘pop’ operation
through the use of a DC Servo to null out any offset on the outputs.
A secondary volume PGA in the output drive stage permits an improvement in SNR for applications
that limit the maximum output voltage. This PGA can be set to attenuate by up to 7dB, as detailed in
Table 29.
Because the secondary volume PGA controlled by HPL_VOL[2:0] and HPR_VOL[2:0] does not have
a Zero Cross functionality, it is designed to be adjusted only during initialisation or periods of silence.
For volume adjustments with a signal playing, it is recommended to use LOUT1VOL and ROUT1VOL.
PP, August 2009, Rev 3.1
w
43
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
