WM8351 datasheet(164/330 Pages) WOLFSON

164 / 330 page

WM8351

Production Data

PD, April 2012, Rev 4.5

164

CHARGER STATUS

CH_IND ACTION

Charger current set to zero

LED off

Trickle charging

LED blinks slowly (0.5Hz)

Fast charging

LED blink s quickly (1Hz)

Table 109 Battery Charger Status via CH_IND

17.7.7

BATTERY FAULT CONDITIONS

The WM8351 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 WM8351 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 0

oC and

oC safe battery charging conditions. The WM8351 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.

WM8351 Datasheet(PDF) 164 Page - Wolfson Microelectronics plc