WM8991 datasheet(91/174 Pages) WOLFSON

91 / 174 page

Pre-Production

WM8991

PP, May 2008, Rev 3.1

TEMPERATURE SENSOR OUTPUT

The WM8991 output drivers can generate a large amount of heat. To protect the device from

overheating a thermal shutdown function is provided (see "Thermal Shutdown" section for more

information).

The polarity of the Thermal Shutdown sensor may be controlled by register bit TEMPOK_POL. Note

that this polarity inversion bit applies to the Interrupt register behaviour only; it does not affect the

direct GPIO output of the Temperature Sensor function. The associated interrupt event may be

masked or enabled by register bit TEMPOK_IRQ_ENA. The Temperature status bit contained in the

IRQ Register (R18) may be read at any time or else in response to an Interrupt event. See Table 55

for more details of the Interrupt function.

If direct output of the Temperature status bit is required to the external pins of the WM8991, the

following register settings are required:

•

ALRCGPIO1 = 1 (only required if using GPIO1)

•

MCLK_SRC = 0 (only required if using GPIO2)

•

AIF_SEL = 0 (only required if using GPIO3, GPIO4 or GPIO5)

•

ALRCGPIO6 = 0 (only required if using GPIO6)

•

AIF_TRIS = 0

•

GPIOn_SEL = 0101 for the selected GPIO Temperature status output pin

•

GPIOn_PU = 0 for the selected GPIO Temperature status output pin

•

GPIOn_PD = 0 for the selected GPIO Temperature status output pin

The register fields used to configure the Temperature Sensor GPIO function are described in Table

51.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R23 (17h)

TEMPOK_POL

(rw)

Temperature Sensor polarity

0 = Non-inverted

1 = Inverted

R22 (16h)

TEMPOK_IRQ_

ENA

Temperature Sensor IRQ Enable

0 = disabled

1 = enabled

Table 51 Temperature Sensor GPIO Control

The temperature sensor function operates according to the following truth table:

LABEL

VALUE

DESCRIPTION

Temperature Sensor output

Overheat temperature exceeded

Temperature Sensor output

Overheat temperature not exceeded

Table 52 Truth table for GPIO Output of Temperature Sensor Function

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