wm8400 Wolfson Microelectronics plc, wm8400 Datasheet - Page 153

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

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Pre-Production
TEMPERATURE SENSING
Table 99 Interrupt Event Control
The WM8400 incorporates a thermal sensor which can be used to prevent damage or hazards in the
event of safe operating temperatures being exceeded. The register fields CHIP_GT115_ERRACT
and CHIP_GT150_ERRACT determine what action is taken at the temperature thresholds 115°C and
150°C respectively. The available options are to signal an Interrupt (IRQ) event only, or to
additionally initiate device shutdown. It is recommended to shut down the WM8400 as soon as
possible if the upper threshold is reached.
If an IRQ event arises from these functions, this causes the NIRQ pin to output a logic low level
(referenced to the MBVDD power domain).
The thermal protection of the audio components of the WM8400 may be controlled independently. If
the device temperature reaches approximately 150ºC and the thermal shutdown circuit is enabled
(TSHUT_ENA = 1; TSHUT_OPDIS = 1) the speaker and headphone amplifiers (LOUT, ROUT,
SPKP, SPKN, OUT3 and OUT4) will be disabled.
Note that TSHUT_ENA must be set to 1 to enable the temperature sensor when using the
TSHUT_OPDIS thermal shutdown function. The output of this temperature sensor can also be output
to the GPIO pins.
Table 100 Thermal Shutdown
When the speaker driver is operating in class AB mode the internal power dissipation of the WM8400
is likely to be significantly higher than when operating in class D mode.
Note: To prevent potential pops and clicks THSUT_ENA and TSHUT_OPDIS need to be configured
while the speaker and headphone outputs are off, i.e. LOUT_ENA, ROUT_ENA, OUT3_ENA,
OUT4_ENA and SPK_ENA are 0 (see also Table 77).
R3 (03h)
R78 (4Eh)
REGISTER
ADDRESS
REGISTER
ADDRESS
BIT
14
13
9
8
BIT
0
TSHUT_ENA
(rw)
TSHUT_OPDIS
(rw)
CHIP_GT150_E
RRACT
CHIP_GT115_E
RRACT
LDO1_UV_LVL
LABEL
LABEL
1b
1b
1b
0b
DEFAULT
DEFAULT
0b
Audio Components Thermal Sensor
Enable
0 = Thermal sensor disabled
1 = Thermal sensor enabled
Audio Components Thermal Shutdown
Enable
(Requires thermal sensor to be
enabled)
0 = Thermal shutdown disabled
1 = Thermal shutdown enabled
Device Overtemperature 2 Action
0 = UVLO generates IRQ only
1 = UVLO generates IRQ and initiates
device shutdown
Device Overtemperature 1 Action
0 = UVLO generates IRQ only
1 = UVLO generates IRQ and initiates
device shutdown
0 = LDO2 voltage normal
1 = LDO2 undervoltage detected
LDO1 Regulator IRQ level
0 = LDO1 voltage normal
1 = LDO1 undervoltage detected
DESCRIPTION
DESCRIPTION
PP, April 2009, Rev 3.0
WM8400
153