User Guide

PAMS Technical Documentation 3. System Module
NSD-5
Issue 1 05/02 Nokia Corporation Page 33
Power Up by IBI
IBI can power CCONT up by setting BTEMP to logical “1”. The recommended pulse width
of the pulse is longer than 10 msec. After that, BTEMP acts as normal A/D input. Other-
wise, the power-up procedure is the same as with the charger.
Power Up With RTC
RTC can power up the phone by setting the CCONT internal signal RTCPwr to logical “1”
Otherwise, the power-up procedure is the same as with the charger.
Charging – CHAPS
CHAPS comprises the hardware for charging the battery and protecting the phone from
over–voltage in charger connector. CHAPS operates in temperature ranges from -30
o
to
130
o
C. The software can stop charging based on the battery temperature to protect the
battery from being damaged (e.g., the cutoff temperature for the nickel battery is 47
o
C;
the cutoff temperature for the lithium battery is 85
o
C). Figure 17 gives a brief block dia-
gram of the charging submodule.
The main functions of CHAPS are:
• protection against transient, over–voltage, and reverse charger voltage
• limited start–up charge current for a totally empty battery
• limit voltage when battery removed
• software protection against overcharging current
CHAPS is basically a PWM (Pulse Width Modulation) controlled switch, which connects
the charger to VBAT. MAD4 controls CHAPS by writing PWM values to CCONT PWM reg-
ister over a serial bus. CCONT then outputs a PWM, which is used by CHAPS to control
the switch. In the case of an external fast charger, the PWM is not available at the sys-
tem connector to control the charger. There are only two wires connected to the
charger. In the case of a dead battery, shorted battery, or a battery below 3.0V, CHAPS
supplies a controlled leakage current of about 180mA through the switch to attempt to
bring the battery voltage up.
Figure 17: Charging block