Real Time Clock; Rtc Backup Battery Charging; Vibra Alerting Device - Nokia NSE-6 SERIES Service Manual

NSE–6
System Module

Real Time Clock

Requirements for a real time clock implementation are a basic clock
(hours and minutes), a calender and a timer with alarm and power on/off
–function and miscellaneous calls. The RTC will contain only the time
base and the alarm timer but all other functions will be implemented with
the MCU software. The RTC needs a power backup to keep the clock
running when the phone battery is disconnected. The backup power is
supplied from a rechargable polyacene battery that can keep the clock
running some ten minutes. If the backup has expired, the RTC clock re-
starts after the main battery is connected. The CCONT keeps MCU in re-
set until the 32kHz source is settled (1s max).
The CCONT is an ideal place for an integrated real time clock as the asic
already contains the power up/down functions and a sleep control with
the 32kHz sleep clock, which is running always when the phone battery is
connected. This sleep clock is used for a time source to a RTC block.

RTC backup battery charging

CHAPS has a current limited voltage regulator for charging a backup bat-
tery. The regulator derives its power from VOUT so that charging can take
place without the need to connect a charger. The backup battery is only
used to provide power to a real time clock when VOUT is not present so it
is important that power to the charging circuitry is derived from VOUT and
that the charging circuitry does not present a load to the backup battery
when 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 of
the regulation voltage.

Vibra Alerting Device

A vibra alerting device is used for giving silent signal to the user of an in-
coming call. The device is placed in the phone. The vibra is controlled by
the MAD via the UI–switch asic.
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PAMS
Technical Documentation
Original 08/98