KX-FT57E - Panasonic Fax Service Manual (repair manual). Page 124

|

125

|

VCC

28

43

IC1

6

VCC

8

1

C64

IC9

+5V

VOLTAGE
DETECTION

BATT

R 76

4

J1

BATT

5V/BATT

48

46

C43

C42

X2

47

RTC

SRAM

IC403

CS

C41

This unit has a lithium battery (BATT) which works for the RAM (IC3) and Real Time Clock IC (RTC, Integrated into the
ASIC:IC1).
The user parameters of the autodial numbers, transmission ID, and system setup data and so on are stored in the RAM
(IC3). The RTC continues functioning even when the power switch is OFF backed up by the lithium battery.

When the power switch is turned ON, power is supplied through IC9 to the RAM (IC3) and RTC.
At this time, the voltages at pin 28 of the RAM and pin 43 of the RTC are +5 V. When the power switch is turned OFF, the
BATT supplies the power to the RAM and RTC through J1, R76 and IC9. At that time, the voltages at pin 28 of the RAM
and pin 43 of the RTC are about +2.5 V. When the power switch is OFF and a voltage of +5 V decreases, the Reset IC
(IC9) outputs the reset signals. Pin 28 of the RAM (IC3) and pin 43 of the RTC become low , then the RAM and RTC go
into the back up mode when the power consumption is lower.