WM8352
Production Data
Chip Temperature Monitoring
The WM8352 has a built-in temperature sensor to monitor the silicon die temperature. If the chip
temperature reaches the thermal warning level, the WM8352 sets the SYS_CHIP_GT115_EINT (see
Section 25) and Battery Charger operation may be paused (this is programmable in Trickle Charge
mode). The charger operation will resume once the chip temperature has dropped below the thermal
warning level.
If the chip temperature reaches the thermal shutdown level, the WM8352 sets the
SYS_CHIP_GT140_EINT interrupt and shuts down. (Battery charging is always terminated in this
case.)
Battery Voltage Detection / Defective Battery Detection
A low battery voltage is an indicator that the battery may be defective or removed.
In trickle charge mode, the battery voltage is checked after 30 minutes of charging, or after a quarter
of the charging time CHG_TIME (the larger of these two times applies). If the battery voltage is less
than the defective battery threshold (nominal value 2.85V) at this time, then the battery charging
stops and the WM8352 sets the CHG_BATT_FAIL_EINT interrupt as defined in Table 111.
The battery failure condition is cleared if the battery voltage rises above the defective battery
threshold. It is also cleared if any of the WM8352 power sources (including BATT) is removed and re-
applied, or if the host processor invokes USB Suspend mode. When the failure condition is cleared,
the charger then reverts back to its initial state, and may re-start if the conditions for charging are
fulfilled (see Section 17.7.2).
If fast charging mode is selected, and the battery voltage is less than the defective battery threshold,
then the WM8352 immediately reverts to trickle charging. If the fault persists, then trickle charging
stops as described above.
PD, February 2011, Rev 4.4
166
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
