WM8985GEFLSLASHR datasheet(72/118 Pages) WOLFSON

72 / 118 page

WM8985

Pre-Production

PP, Rev 3.4, October 2006

ENABLING THE OUTPUTS

Each analogue output of the WM8985 can be independently enabled or disabled. The analogue

mixer associated with each output has a separate enable bit. All outputs are disabled by default. To

save power, unused parts of the WM8985 should remain disabled.

Outputs can be enabled at any time, but it is not recommended to do so when BUFIO is disabled

(BUFIOEN=0), as this may cause pop noise (see “Power Management” and “Applications

Information” sections).

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

BUFIOEN

Unused input/output bias buffer enable

OUT3MIXEN

OUT3 mixer enable

R1 (01h)

Power

Management

OUT4MIXEN

OUT4 mixer enable

ROUT1EN

ROUT1 output enable

LOUT1EN

LOUT1 output enable

R2 (02h)

Power

Management

SLEEP

0 = Normal device operation

1 = Supply current reduced in device

standby mode when clock supplied

LMIXEN

Left mixer enable

RMIXEN

Right mixer enable

LOUT2EN

LOUT2 output enable

ROUT2EN

ROUT2 output enable

OUT3EN

OUT3 enable

R3 (03h)

Power

Management

OUT4EN

OUT4 enable

Note:

All “Enable” bits are 1 = ON, 0 = OFF

Table 39 Output Stages Power Management Control

THERMAL SHUTDOWN

To protect the WM8985 from becoming too hot, a thermal sensor has been built in. If the device

junction temperature reaches approximately 125

°C and the TSDEN and TSOPCTRL bit are set, then

all outputs will be disabled to avoid further increase of the chip temperature.

Additionally, when the device is too hot and TSDEN is set, then the WM8985 de-asserts GPIO bit

11, a virtual GPIO that can be set up to generate an interrupt to the CPU (see “GPIO and Interrupt

Control” section).

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

TSDEN

Thermal Sensor Enable

0 = disabled

1 = enabled

R49 (31h)

Output Control

TSOPCTRL

Thermal Shutdown Output enable

0 = Disabled

1 = Enabled, i.e. all outputs will be

disabled if TI set and the device junction

temperature is more than 125ºC.

Table 40 Thermal Shutdown

UNUSED ANALOGUE INPUTS/OUTPUTS

Whenever an analogue input/output is disabled, it remains connected to a voltage source (AVDD1/2)

through a resistor. This helps to prevent pop noise when the output is re-enabled. The resistance

between the voltage buffer and the output pins can be controlled using the VROI control bit. The

default impedance is low, 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 30k

Ω.

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