WM8961
Pre-Production
Figure 27 DC Servo Block Diagram
DC SERVO STARTUP OPERATION
The DC servo contains automatic control circuitry and can be configured using individual register
writes.
The DC servo can also be configured by starting a sequence using the control write sequencer (see
“Control Write Sequencer” section). Starting the pre-defined sequence from line 0 of the control write
sequencer configures the DC servo by default.
The basic startup operation of the DC servo, for example for HP_R, is to
1. Enable the DC Servo operation on the HP_R output by configuring R61[3],
DCS_ENA_CHAN_HPR. (The HP_L, INR/L have similar enables).
2. Trigger
a
start
up
sequence
for
the
HP_R
by
configuring
R61[2]
DCS_TRIG_STARTUP_HPR (The HP_L, INR/L have similar start up sequence enables).
Additionally, to enable the DC servo for L/RINPUT, the headphone charge pump must be enabled
(CP_ENA = 1) and MCLK must be applied.
Note that it is recommended to perform a calibration of the DC Servo input channel before using the
Input PGA Zero Cross Detector.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
DC Servo enabled on channel INL
R60 (3Ch)
DC Servo 1
7
6
DCS_ENA_CHAN_INL
0
0
Perform startup sequence on channel INL*see note
1
DCS_TRIG_STARTUP_INL
DC Servo enabled on channel INR
3
2
DCS_ENA_CHAN_INR
0
0
Perform startup sequence on channel INR *see
note 1
DCS_TRIG_STARTUP_INR
DC Servo enabled on channel HPL
R61 (3Dh)
DC Servo 1
7
6
DCS_ENA_CHAN_HPL
0
0
Perform startup sequence on channel HPL *see
note 1
DCS_TRIG_STARTUP_HPL
DC Servo enabled on channel HPR
3
2
DCS_ENA_CHAN_HPR
0
0
Perform startup sequence on channel HPR *see
note 1
DCS_TRIG_STARTUP_HPR
Table 37 DC Servo Enable and Start-up Configuration
Note:
1. The “startup” bits are automatically reset to ‘0’ after 1 clock cycle.
PP, August 2009, Rev 3.1
w
54
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
