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REV.-A
2.3.1.5 ST-RAM (1
Battery Backup Circuit
The ST-RAM (1
employes a lithium battery (3.00 to 3.35
for backup, and is used to maintain
the initial data for the printer mechanism and settings for the control panel
when the printer power
is turned off.
Figure 2-41 shows the ST-RAM (1
battery backup circuit, and Table 2-32 shows the ST-RAM
conditions when the power is turned on or off.
+ 5
4
ZD6
Q19
CN7
D17
2 2
B A T T E R Y 1
-
--- ‘
u
-
‘ ;
/
2 8
m
3.00
-
-
-
‘-
-
-’
S T - R A M
–
3.35(v)
4
(1
—
\
777
Figure 2-41. Battery Backup Circuit
When the power is turned on under normal conditions, + 5V is applied to
of the ST-RAM, and the
CPU starts read/write operations. When the power is turned off, and the voltage on the + 5V line drops
to about 3.3V or less, transistors Q 19 and Q20 turn off, and the voltage from the external lithium battery
is applied to the
terminal of the ST-RAM. In this way, the data in the ST-RAM is maintained.
When the voltage from the lithium battery drops, the message “RAM CLEAR” is displayed on the LCD
when the printer power is turned on.
Table 2-32. ST-RAM Conditions with Power ON/OFF
Printer Power
+5 V Line
22)
[v]
S T - R A M M o d e
OFF
L
2.4- 2.7*
2
Standby*
3
H
H
I
+5
Normal
I
Must be 0.2 V or less
Must be 2.0 V or
m o r e
Data hold
N O T E : L = O V, H = 5V
Reference: Power consumption at standby: 0.002 [mA] TYP.
2-47
Summary of Contents for LQ-2550
Page 1: ...L Q 2 5 5 0 TECHNICAL MANUAL EPSON ...
Page 240: ...REV A P r cl Figure 6 3 LQ 2550 Lubrication and Adhesive Application Points Diagram 2 6 3 ...
Page 241: ...REV A 7 i_ Figure 6 4 LQ 2550 Lubrication and Adhesive Application Points Diagram 3 6 4 ...
Page 252: ...REV A I 1 I 7 v m o m x b Figure A 6 PPD781OHG Block Diagram A 7 ...
Page 297: ...REV A 1 L I Irl N I i t 1 I I x Figure A 50 ROPSE Board Circuit Diagram A 52 ...