Samsung SCH-470, Service Manual

Page: 23 / 66

Circuit Description
Samsung Electronics 5-9
DETECTION OF BATTERY TYPE
The battery type in the front port is detected by
R54, R56, and the resistor which is connected
between the battery C/F and ground terminal, and
measured at the pin 15 of the MPU through U26.
The battery type in the rear port is detected by
R53, R57, and the resistor which is connected
between the battery C/F and ground terminal, and
measured at the pin 15 of the MPU through U26.
DETECTION OF AMBIENT TEMPERATURE
TH21 is a thermistor which is used to detect the
ambient temperature. It has a linear characteristic
by R51 and R52, and is measured at the pin 14 of
the MPU through U25.
MEASURING CHARGING CURRENT
The charging current is converted through U23-A
to the voltage Vi which is proportional to the
current. The noise of Vi is eliminated with R71 and
C30. Finally the voltage Vi is measured at the pin
12 of the MPU.
AUTONOMOUS TIMER
If the MPU stops its operation with the charging
port on due to an accidental shock (for example,
drop), the battery may become overcharged. The
external timer U23-B is equipped to protect the
battery from being overcharged. If the timer is not
reset within a specified time by MPU, MPU will be
automatically reset by the timer.