Production Data
WM8352
17.7.7 BATTERY FAULT CONDITIONS
The WM8352 continuously monitors battery temperature, chip temperature and battery voltage. In
case of a fault condition, it autonomously takes appropriate action, and alerts the host processor via
the applicable interrupt flags.
Battery Temperature Monitoring
The WM8352 can monitor the battery temperature via the NTC (negative temperature coefficient)
resistor which is incorporated into suitable battery packs. The NTC resistor must be connected to the
AUX1 pin as shown in Section 17.7.1. Typical NTC resistor values vary over a range of temperature
(source of information is Vishay Dale’s “R-T Curve 2”).
The NTC monitoring circuit is designed to detect temperature conditions outside the typical 0oC and
45oC safe battery charging conditions. The WM8352 indicates a cold battery temperature condition is
indicated by setting the CHG_BATT_COLD_EINT interrupt. A hot battery temperature is indicated by
setting the CHG_BATT_HOT_EINT interrupt. Battery charging is suspended when either of these
conditions is set. (Note that trickle charging will resume once the battery temperature has returned to
within normal levels.)
It is possible to disable the NTC detection circuit and associated flags. This option is protected by a
security key. The associated register bits are described in Table 110.
Safety warning - The battery temperature sensor is a safety mechanism and it is strongly
recommended that it be used, as directed, in all applications requiring charger functionality. Disabling
this feature by any means, intentional or otherwise, could result in incorrect behaviour of the battery
charger function.
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R168 (A8h)
3
CHG_NTC_M
ON
1
Enable charger battery NTC detection
(some batteries may not need this - turn
off with caution)
Battery
Charger
Control 1
0 = Charger ignores NO_NTC detection.
1 = Charger monitors NO_NTC detection.
Protected by user key, read-only in ROM
configs.
2
CHG_BATT_H
OT_MON
1
Enable charger battery temperature high
detection (some batteries may not need
this - turn off with caution)
0 = Charger ignores battery temperature
too high.
1 = Charger monitors battery temperature
too high.
Protected by user key, read-only in ROM
configs.
1
CHG_BATT_C
OLD_MON
1
Enable charger battery temperature low
detection (some batteries may not need
this - turn off with caution)
0 = Charger ignores battery temperature
low.
1 = Charger monitors battery temperature
low.
Protected by user key, read-only in ROM
configs.
Note: Some batteries may not require battery temperature monitoring. Disable with caution.
Table 110 Battery Temperature Monitoring
PD, February 2011, Rev 4.4
165
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
