WM8758B datasheet(59/90 Pages) WOLFSON

59 / 90 page

Production Data

WM8758B

PD, Rev 4.4, January 2012

ENABLING THE OUTPUTS

Each analogue output of the WM8758B 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 WM8758B 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

Power

Management

BUFIOEN

Unused input/output bias buffer enable

OUT3MIXEN

OUT3 mixer enable

OUT4MIXEN

OUT4 mixer enable

Power

Management

ROUT1EN

ROUT1 output enable

LOUT1EN

LOUT1 output enable

SLEEP

0 = Normal device operation

1 = Supply current reduced in device

standby mode (see note)

Power

Management

LMIXEN

Left mixer enable

RMIXEN

Right mixer enable

ROUT2EN

ROUT2 output enable

LOUT2EN

LOUT2 output enable

OUT3EN

OUT3 enable

OUT4EN

OUT4 enable

Note:

All “Enable” bits are 1 = ON, 0 = OFF

Table 38 Output Stages Power Management Control

Note: The SLEEP bit R2[6] should only be used when the device is already in standby mode. The

SLEEP bit prevents the MCLK from propagating round the device when the external MCLK signal

cannot be removed.

THERMAL SHUTDOWN

To protect the WM8758B from becoming too hot, a thermal sensor has been built in. If the chip

temperature reaches approximately 150

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 WM8758B 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

R49

Output Control

TSDEN

Thermal Sensor Enable

0 = disabled

1 = enabled

TSOPCTRL

Thermal Shutdown Output enable

0 = Disabled

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

disabled if TI set, i.e. temperature above

150ºC

Table 39 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

.

WM8758B Datasheet(PDF) 59 Page - Wolfson Microelectronics plc

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