A3.1.6.3 Backup Circuit - OKIDATA OKIFAX 5700 Maintenance Manual

A3.1.6.3 Backup circuit

A rechargeable battery connected to the MCNT board externally supplies 6 V to the IC
inside the MCNT board. This voltage is reduced to 3.3 V to be supplied to the DRAM and
optional add-on memory. Thus, send/received data stored in the DRAM and optional add-
on memory can be retained after power-off.
When the power is turned on, the internal IC reduces the +8 V and +5 V supplied from low-
voltage power supplies down to 3.3 V, which is supplied to the DRAM. At the same time,
+8 V is supplied to the external battery for recharging.
A block diagram is shown below.
+8V
+5V
MCNT board
OKIFAX 5700/5900
6VB
CN18
0V
+3.3V
VOLTAGE
Reg
DRAM
(8MB)
Add-on memory
DRAM
A3 - 13
R76-/R76-2
External
rechargeable
battery