Nokia NSE–3 SERIES Service Manual

Contents

Nokia NSE–3 SERIES Service Manual Manual pdf 26 page image

PAMSTechnical DocumentationNSE–3System ModuleOriginal 11/97Page 3 – 20Battery Removal During ChargingOutput overvoltage protection is also needed in case the main battery isremoved when charger connected or charger is connected before the bat-tery is connected to the phone.With a charger connected, if VOUT exceeds VLIM1 (or VLIM2), CHAPSturns switch OFF until the charger input has sunken below Vpor (nominal3.0V, maximum 3.4V). MCU software will stop the charging (turn offPWM) when it detects that battery has been removed. The CHAPS re-mains in protection state as long as PWM stays HIGH after the outputovervoltage situation has occured.PWMtVOUTt4VVLIM”1””0”SWITCHtONOFF21.1Battery removed, (standard) charger connected, VOUT rises (follows charger voltage)2. VOUT exceeds limit VLIM(X), switch is turned immediately OFF3.3VOUT falls (because no battery) , also VCHoutput). When VCH > Vpor and VOUT < VLIM(X) –> switch turned on again (also PWMis still HIGH) and VOUT again exceeds VLIM(X).44. Software sets PWM = LOW –> CHAPS does not enter PWM modeVstart55. PWM low –> Startup mode, startup current flows until Vstart limit reachedVCH(StandardCharger)VporVstarthysDroop depends on loadIstart off due to VCH& C in phone66. VOUT exceeds limit Vstart, Istart is turned off7. VCH falls below Vpor7