Nokia NSE–3 SERIES Service Manual

Contents

Nokia NSE–3 SERIES Service Manual Manual pdf 52 page image

PAMSTechnical DocumentationNSE–3System ModuleOriginal 11/97Page 3 – 46RTC backup battery chargingCHAPS has a current limited voltage regulator for charging a backup bat-tery. The regulator derives its power from VOUT so that charging can takeplace without the need to connect a charger. The backup battery is onlyused to provide power to a real time clock when VOUT is not present so itis important that power to the charging circuitry is derived from VOUT andthat the charging circuitry does not present a load to the backup batterywhen VOUT is not present.It should not be possible for charging current to flow from the backup bat-tery into VOUT if VOUT happens to be lower than VBACK. Charging cur-rent will gradually diminish as the backup battery voltage reaches that ofthe regulation voltage.Vibra Alerting DeviceA vibra alerting device is used for giving silent signal to the user of an in-coming call. The device is not placed in the phone but it will be added to aspecial battery pack. The vibra is controlled with a PWM signal by theMAD via the BTEMP battery terminal.A 15kohm BSI resistor is needed to detect the vibra battery. It is only usedto enable vibra selection in user menu. When alerting, VibraPWM signalis delivered to battery.47kNTCBATTERYVibra10n100kVREFTRANSCEIVERBTEMPGNDBSIVBAT10n1kMADBTEMP CCONTVIBRAPWMC1R3MCUGenIO410k22kR T100n 1k