WM8973CLGEFLSLASHV datasheet(37/63 Pages) WOLFSON

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Production Data

WM8973L

PD, Rev 4.5, December 2011

ENABLING THE OUTPUTS

Each analogue output of the WM8973L can be separately enabled or disabled. The analogue mixer

associated with each output is powered on or off along with the output pin. All outputs are disabled by

default. To save power, unused outputs should remain disabled.

Outputs can be enabled at any time, except when VREF is disabled (VR=0), as this may cause pop

noise (see “Power Management” and “Applications Information” sections)

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R26 (1Ah)

Power

Management

(2)

LOUT1

LOUT1 Enable

ROUT1

ROUT1 Enable

LOUT2

LOUT2 Enable

ROUT2

ROUT2 Enable

MONO

MONOOUT Enable

OUT3

OUT3 Enable

Note: All “Enable” bits are 1 = ON, 0 = OFF

Table 29 Analogue Output Control

Whenever an analogue output is disabled, it remains connected to VREF (pin 20) through a resistor.

This helps to prevent pop noise when the output is re-enabled. The resistance between VREF and

each output can be controlled using the VROI bit in register 27. The default is low (1.5k

), so that any

capacitors on the outputs can charge up quickly at start-up. If a high impedance is desired for

disabled outputs, VROI can then be set to 1, increasing the resistance to about 40k

.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R27 (1Bh)

Additional (1)

VROI

VREF to analogue output resistance

0: 1.5 k



1: 40 k



Table 30 Disabled Outputs to VREF Resistance

HEADPHONE SWITCH

The RINPUT3/HPDETECT pin can be used as a headphone switch control input to automatically

disable the speaker output and enable the headphone output e.g. when a headphone is plugged into

a jack socket. In this mode, enabled by setting HPSWEN, HPDETECT switches between headphone

and speaker outputs (e.g. when the pin is connected to a mechanical switch in the headphone socket

to detect plug-in). The HPSWPOL bit reverses the pin’s polarity. Note that the LOUT1, ROUT1,

LOUT2 and ROUT2 bits in register 26 must also be set for headphone and speaker output (see Table

31 and Table 32).

Note:

When RINPUT3/HPDETECT is used as the HPDETECT input, the thresholds become CMOS levels

(0.3 AVDD / 0.7 AVDD).

HPSWEN

HPSWPOL HPDETECT

(PIN23)

L/ROUT1

(reg. 26)

L/ROUT2

(reg. 26)

Headphone

enabled

Speaker

enabled

yes

Table 31 Headphone Switch Operation

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