Table of Contents
Advertisement
Circuit Description
4-6-2 Schematic Description
DC-DC CONTROLLER
KA7500B(U1) is DC-DC Controller. It reads the
voltage difference between E1I+ Port and E1I- Port
and controls time to turn on Q1. E2I+ and E2I-
turn on Q1 in the same way. U1 also supplies +5V
of Reference Voltage(Vref).
STATIC CURRENT
E1I- Port of U1 detects about 1.25V untill Full-
Charge and controls the TURN ON time of Q1 in
order to detect 1.25V at E1I+ Port. To make the
E1I+ Port detect 1.25V continuously, 0.19V of
voltage reduction will be generated on R4. At the
equation of V=I*R, the current of R4 is around
390mA and it will be the charge current.
BATTERY CHARGE CURRENT CUTTING BY
RELATIVE TEMPERATURE
Although every battery sample applied to the
SCH-1000 has almost the same battery
temperature at Full-Charge, it varies according to
the relative temperature.
So the battery temperature at Full-Charge may be
different according to the temperature around the
cellular phone.
If Full-Charge occures at 25°..., the voltage of U3C
to which the battery thermistor is connected is
around 2.11V and the voltage of the parallel
resistance of Th1 and R18 is about 2.11V. PIN 8 of
U3C will be HIGH and turn on Q3 if the
temperature is up. This generates the voltage
detected at E1I- of U1 around 0.1V and the charge
current reduces to 40mA. If Full-Charge occurs at
high temperature and low temperature, the battery
temperature varies and the voltage decline of Th1
and R18 relatively varies. So the battery Full-
Charge condition will be fulfilled.
4-10
PREVENT CHARGE CIRCUIT IN THE CASE
OF MOBILE PHONE CARRIER-ON
In the case of Mobile Phone carrier-on, the voltage
loaded on PIN-13 of U3D is lower than that of
PIN-12. So PIN-14 ouputs HIGH and Q3 is TURN
ON again. It results to the Prevent Charge.
LED-DRIVING CIRCUIT
When battery is inserted to CLC, the voltage
loaded to PIN-2 of U3A is lower than that of PIN-3
and PIN-1 outputs HIGH. This TURN ON Q7 and
drives LED.
Samsung Electronics
Advertisement
Table of Contents
