wm8400 Wolfson Microelectronics plc, wm8400 Datasheet - Page 106

• Manufacturer Part Number: wm8400
• Description: Wolfson Audioplustm Hi-fi Audio Codec And Power Management Unit For Mobile Multimedia
• Manufacturer: Wolfson Microelectronics plc

WM8400
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TEMPERATURE SENSOR OUTPUT
The WM8400 incorporates a temperature sensor which detects when the device temperature is
within normal limits or if the device is approaching a hazardous temperature condition. The
temperature status may be output directly on a GPIO pin, and may also be used to generate CODEC
Interrupt events. Configuration of the GPIO pins for Temperature Sensor output is described in Table
63 and Table 64 and also in the example settings below.
The temperature sensor signal is an input to the CODEC Interrupt function, with selectable enable
and polarity control. The associated interrupt bit (TEMPOK) is latched once set and can be polled at
any time or used to trigger the CODEC IRQ output. The interrupt bit is reset by writing a logic ‘1’ to
the TEMPOK register bit. See “CODEC Interrupt Event Output” for more details of the CODEC
Interrupt event handling.
Note that the temperature sensor can be configured to automatically disable the audio outputs of the
WM8400 (see “Thermal Shutdown”). In some applications, it may be preferable to manage the
temperature sensor event through GPIO or Interrupt functions, allowing a host processor to
implement a controlled system response to an over-temperature condition.
The temperature sensor must be enabled by setting the TSHUT_ENA register bit. When the
TSHUT_OPDIS is also set, then a device over-temperature condition will cause the audio outputs of
the WM8400 to be disabled.
The Temperature Sensor output is asserted when the device is within normal operating limits. When
configured to generate an interrupt event, the default polarity (TEMPOK_POL = 1) will cause an
interrupt event when an overtemperature condition has been reached.
If direct output of the Temperature status bit is required to the external pins of the WM8400, the
following register settings are required:
When GPIOn_SEL = 0101, the Temperature Sensor status is output on the GPIOn pin. A logic 0
indicates that an overtemperature condition has been reached. Note that the polarity is not
programmable for GPIO output; the GPIO_POL and TEMPOK_POL fields affect the Interrupt
behaviour only.
The register fields used to configure the Temperature Sensor GPIO function are described in Table
66.
Note that the Temperature Sensor also provides input to the Main Interrupt circuit on the WM8400,
configured in Registers R79 - R81, and signalled externally on the NIRQ pin. Two different
temperature thresholds can be monitored in this way. See “Interrupt Events” for details.
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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
PP, April 2009, Rev 3.0
Pre-Production
106