WM8945ECSSLASHR datasheet(64/169 Pages) WOLFSON

64 / 169 page

WM8945

Production Data

PD, May 2011, Rev 4.1

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.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R2 (02h)

Power

management

VMID_BUF_ENA

VMID Buffer Enable.

(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

0 = Disabled

1 = Enabled

SPKL_VMID_OP

_ENA

Buffered VMID to SPKOUTL Enable

0 = Disabled

1 = Enabled

LINEL_VMID_OP

_ENA

Buffered VMID to LINEOUTL

Enable

0 = Disabled

1 = Enabled

SPK_VROI

Buffered VREF to SPKOUTL /

SPKOUTR resistance (Disabled

outputs)

0 = approx 20k

1 = approx 1k

LINE_VROI

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.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R42 (2Ah)

Output ctrl

SPKR_DISCH

Discharges SPKOUTR output via

approx 4k resistor

0 = Not active

1 = Actively discharging SPKOUTR

SPKL_DISCH

Discharges SPKOUTL output via

approx 4k resistor

0 = Not active

1 = Actively discharging SPKOUTL

LINEL_DISCH

Discharges LINEOUTL output via

approx 4k resistor

0 = Not active

1 = Actively discharging LINEOUTL

Table 42 Output Discharge Control

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