WM8325 Datasheet, PDF (137/254 Pages) Wolfson Microelectronics plc – Processor Power Management Subsystem

Production Data
WM8325
26 TEMPERATURE SENSING
The WM8325 provides temperature monitoring as status information and also for self-protection of the
device. Temperature monitoring is always enabled in the ON and SLEEP states.
The thermal warning temperature can be set using the THW_TEMP register field. The thermal
warning hysteresis ensures that the THW_TEMP is not reset until the device temperature has
dropped below the threshold by a suitable margin. The extent of the hysteresis can be selected using
the THW_HYST register field.
The Thermal Warning condition can be read using the THW_STS register bit. An overtemperature
condition causes the thermal warning interrupt (TEMP_THW_CINT) to be set. The thermal warning
interrupt is also set when the overtemperature condition clears, ie. when the device has returned to its
normal operating limits.
The thermal shutdown temperature is set at a fixed level. If a thermal shutdown condition is detected
whilst in the ON or SLEEP states, then a System Reset is triggered, as described in Section 24.1,
forcing a transition to the OFF state.
The temperature sensing circuit is configured and monitored using the register fields described in
Table 81.
ADDRESS
R16386
(4002h)
BIT
LABEL
3 THW_HYST
1:0 THW_TEMP
[1:0]
DEFAULT
1
10
R16397
15 THW_STS
0
(400Dh)
Table 81 Temperature Sensing Control
DESCRIPTION
Thermal Warning hysteresis
0 = 8 degrees C
1 = 16 degrees C
Thermal Warning temperature
00 = 90 degrees C
01 = 100 degrees C
10 = 110 degrees C
11 = 120 degrees C
Thermal Warning status
0 = Normal
1 = Overtemperature Warning
(warning temperature is set by THW_TEMP)
The thermal warning interrupt event is indicated by the TEMP_THW_CINT register field. This
secondary interrupt triggers a primary Thermal Interrupt, TEMP_INT (see Section 23). This can be
masked by setting the mask bit as described in Table 82.
ADDRESS
R16401
(4011h)
Interrupt Status
1
R16410
(4019h)
Interrupt Status
1 Mask
BIT
LABEL
1
TEMP_THW_CINT
1
IM_TEMP_THW_CINT
Table 82 Thermal Interrupts
DESCRIPTION
Thermal Warning interrupt
(Rising and Falling Edge triggered)
Note: Cleared when a ‘1’ is written.
Interrupt mask.
0 = Do not mask interrupt.
1 = Mask interrupt.
Default value is 1 (masked)
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PD, February 2012, Rev 4.0
137