wm8961 Wolfson Microelectronics plc, wm8961 Datasheet - Page 43

• Manufacturer Part Number: wm8961
• Description: Ultra-low Power Stereo Codec With 1w Stereo Class D Speaker Drivers And Ground Referenced Headphone Drivers
• Manufacturer: Wolfson Microelectronics plc

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WM8961
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.
R2 (02h)
LOUT1
Volume
R3 (03h)
ROUT1
Volume
R26 (1Ah)
Power
Management
(2)
REGISTER
ADDRESS
8
7
6:0
8
7
6:0
6
5
BIT
OUT1VU
LO1ZC
LOUT1VOL
[6:0]
OUT1VU
RO1ZC
ROUT1VOL
[6:0]
LOUT1_PGA
ROUT1_PGA
LABEL
0
0
0000000
(MUTE)
0
0
0000000
(MUTE)
0
0
DEFAULT
Headphone Volume Update
0 = Store LOUT1VOL in intermediate
latch (no gain change)
1 = Update left and right channel gains
(left = LOUT1VOL, right = intermediate
latch)
Left zero cross enable
0 = Change gain immediately
1 = Change gain on zero cross only
LOUT1 Volume
1111111 = +6dB
… 1dB steps down to
0110000 = -73dB
0101111 to 0000000 = Analogue
MUTE
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
ROUT1 Volume
Similar to LOUT1VOL
LOUT1 left headphone PGA Output
Enable
ROUT1 right headphone PGA Output
Enable
DESCRIPTION
PP, August 2009, Rev 3.1
Pre-Production
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