WM8945
Production Data
The buffered VMID reference is enabled by setting VMID_BUF_ENA. This is applied to any disabled
outputs, provided that the respective _VMID_OP_ENA bit is also set. The output resistance can be
either 1k or 20k, depending on the respective _VROI register bit.
The disabled output control bits are described in Table 41. See “Output Signal Path” for details of how
to disable any of the audio outputs.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R2 (02h)
VMID_BUF_ENA
VMID Buffer Enable.
2
0
Power
management
1
(The buffered VMID may be applied
to disabled input and output pins.)
0 = Disabled
1 = Enabled
R42 (2Ah)
Output ctrl
SPKR_VMID_OP
_ENA
Buffered VMID to SPKOUTR
Enable
13
0
0 = Disabled
1 = Enabled
SPKL_VMID_OP
_ENA
Buffered VMID to SPKOUTL Enable
0 = Disabled
12
10
0
0
1 = Enabled
LINEL_VMID_OP
_ENA
Buffered VMID to LINEOUTL
Enable
0 = Disabled
1 = Enabled
SPK_VROI
LINE_VROI
Buffered VREF to SPKOUTL /
SPKOUTR resistance (Disabled
outputs)
1
0
0
0
0 = approx 20k
1 = approx 1k
Buffered VREF to LINEOUTL
resistance (Disabled output)
0 = approx 20k
1 = approx 1k
Table 41 Disabled Output Control
OUTPUT DISCHARGE CONTROL
The line outputs and speaker outputs can be actively discharged to GND through internal resistors if
desired. This is desirable at start-up in order to achieve a known output stage condition prior to
enabling the soft-start VMID reference voltage. This is also desirable in shut-down to prevent the
external connections from being affected by the internal circuits.
The individual control bits for discharging each audio output are described in Table 42.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R42 (2Ah)
Output ctrl
SPKR_DISCH
Discharges SPKOUTR output via
approx 4k resistor
7
0
0 = Not active
1 = Actively discharging SPKOUTR
SPKL_DISCH
LINEL_DISCH
Discharges SPKOUTL output via
approx 4k resistor
6
4
0
0
0 = Not active
1 = Actively discharging SPKOUTL
Discharges LINEOUTL output via
approx 4k resistor
0 = Not active
1 = Actively discharging LINEOUTL
Table 42 Output Discharge Control
PD, May 2011, Rev 4.1
64
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
