Charging; Watchdog - Nokia NSB-7 Series Service Manual

NSB-7
System Module

Charging

Charging can be performed in any operating mode.The battery type/size is indicated by a
resistor inside the battery pack. The resistor value corresponds to a specific battery
capacity. This capacity value is related to the battery technology as different capacity
values are achieved by using different battery technology.
The battery voltage, temperature, size and current are measured by the CCONT controlled
by the charging software running in the MAD.
The power management circuitry controls the charging current delivered from the
charger to the battery. Charging is controlled with a PWM input signal, generated by the
CCONT. The PWM pulse width is controlled by the MAD and sent to the CCONT through a
serial data bus. The battery voltage rise is limited by turning the CHAPS switch off when
the battery voltage has reached 4.2 V. Charging current is monitored by measuring the
voltage drop across a 220 mohm resistor.

Watchdog

The Watchdog block inside CCONT contains a watchdog counter and some additional
logic which are used for controlling the power on and power off procedures of CCONT.
Watchdog output is disabled when WDDisX pin is tied low. The WD–counter runs during
that time, though. Watchdog counter is reset internally to 32 s at power up. Normally it
is reset by MAD writing a control word to the WDReg.
Page 26 ãNokia Mobile Phones Ltd.
PAMS Technical Documentation
Issue 1 06/00