User Guide

PAMS
Technical Documentation
NSE–3
System Module
Original 11/97
Page 3 – 46
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 not placed in the phone but it will be added to a
special battery pack. The vibra is controlled with a PWM signal by the
MAD via the BTEMP battery terminal.
A 15kohm BSI resistor is needed to detect the vibra battery. It is only used
to enable vibra selection in user menu. When alerting, VibraPWM signal
is delivered to battery.
47k
NTC
BATTERY
Vibra
10n
100k
VREF
TRANSCEIVER
BTEMP
GND
BSI
VBAT
10n
1k
MAD
BTEMP
CCONT
VIBRAPWM
C1
R3
MCUGenIO4
10k
22k
R
T
100n
1k