Memory Back-Up Circuit - Aficio 5000L Service Manual

November 29, 1999

1.4.2 MEMORY BACK-UP CIRCUIT

+5V
+
CN51
IC Card
+5VE
The +5VBAT supply from the lithium battery [BAT2] backs up the system RAM,
which contains system parameters, programmed telephone numbers, and the real
time clock in the main CPU. The 5RTCCS signal tells the main CPU whether the
back-up power (+5VBAT) is coming from the battery or from the +5V power supply.
A rechargeable lithium battery [BAT1] and the DC/DC converter on the FCU back
up the DRAM (SAF memory) for one hour, if there is data in the SAF memory and
the power is switched off. While the main power is on, the +5VE supply recharges
the battery. The battery recharges in 5 or 6 days.
There is no battery switch for the battery [BAT1].
5 P O W E R S
Switching
5 R T C C S
Circuit
-
System
R A M
+5VD
1-17
POWER DISTRIBUTION
1SAFFG
S C P
1 V D E T
D R A M
+ 5 V B A T
+5VD +5VE
D C / D C
Converter
Comparator
F C U
H306V507.WMF