WM8987LGECOSLASHV datasheet(34/58 Pages) WOLFSON

34 / 58 page

WM8987L

Pre-Production

PP Rev 3.0 January 2007

ENABLING THE OUTPUTS

The analogue outputs and output mixers of the WM8987L can be separately enabled or disabled as

shown in Table 29.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

ROUT1

Enables ROUT1 and right mixer

LOUT2

Enables LOUT2 and left mixer

ROUT2

Enables ROUT2 and right mixer

MONO

Enable mono mixer

R26 (1Ah)

Power

Management

(2)

OUT3

Enables OUT3

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

Table 29 Analogue Output Control

All outputs and mixers are disabled by default. To save power, they should remain disabled

whenever possible. 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).

Whenever an analogue output is disabled, it remains connected to the VREF voltage through an

internal 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

Ω), 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

Ω.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R27 (1Bh)

Additional (1)

VROI

VREF to analogue output resistance

0: 1.5 k

Ω

1: 40 k

Ω

Table 30 Disabled Outputs to VREF Resistance

THERMAL SHUTDOWN

The analogue outputs can drive large currents. To protect the WM8987L from overheating, a thermal

shutdown circuit is included. If the device temperature reaches approximately 150

0C and the thermal

shutdown circuit is enabled (TSDEN = 1) then the output amplifiers (pins ROUT1, LOUT2, ROUT2

and OUT3) are disabled.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R23 (17h)

Additional

Control (1)

TSDEN

Thermal Shutdown Enable

0 : thermal shutdown disabled

1 : thermal shutdown enabled

Table 31 Thermal Shutdown

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