User Guide

NSB-5

System Module PAMS Technical Documentation

Page 26 Nokia Mobile Phones Ltd. Issue 1 03/01

When the switch in output overvoltage situation has once turned OFF, it stays OFF until

the the battery voltage falls below VLIM1 (or VLIM2) and PWM = LOW is detected. The

switch can be turned on again by setting PWM = HIGH.

Battery Removal During Charging

Output overvoltage protection is also needed in case the main battery is removed when

charger connected or charger is connected before the battery is connected to the phone.

With a charger connected, if VOUT exceeds VLIM1 (or VLIM2), CHAPS turns switch OFF

until the charger input has sunken below Vpor (nominal 3.0V, maximum 3.4V). MCU soft-

ware will stop the charging (turn off PWM) when it detects that battery has been

removed. The CHAPS remains in protection state as long as PWM stays HIGH after the

output overvoltage situation has occurred.

PWM (32Hz)

VOUT

VLIM1 or VLIM2

SWITCH

ON OFF

VCH

VCH<VOUT