EPSON Stylus Color 900 Revision C
Operating Principles Electrical Circuit Operation Principles 61
The control circuits are explained in detail below.
[Combined (reset circuit + timer) circuit]
A combined circuit RTC9810 manages both reset signal production and
RTC (Rear Time Controller). It produces reset signals by monitoring the
both 5 VDC line (input to Pin 7) and 42 VDC line (input to Pin 9). When
the voltage level for the 5 VDC line drops to 4.3 V, or the voltage level
for the 42 VDC line drops to 35.5 V, the combined circuit outputs a reset
signal from Pin 2. When the printer is turned on / off or detects abnormal
voltage level, the IC sends the reset signal to the following ICs to avoid
printer damage caused by run-away of the logic line and abnormal
operation of driver systems. Also, to let the motor driver IC execute its
job properly, the reset signal is once input to the convertor (setting
current production IC) on the main board to stop motors in the correct
sequence.
On the other hand, the timer control is done by counting the operation of
the oscillator circuit, and the printer’s power off time can be confirmed
based on the timer at the next power on operation. Also, this count data
is used to manage the timer for the operation such as periodical flashing
during power on time as well as power off time.
While the printer is on, the printer supplies 5 V (input to Pin 7) to operate
the internal oscillation circuit, however, when the printer is turned off,
the external button-cell battery (a lithium battery) immediately starts
supplying voltage (3 V) to the Pin 8.
Figure 2-12. Reset/timer combined circuit
+42 V
Speed up
diode
+5 V
R18 107 K
R20 10 K
BAT1
VIN
VDD
VBK
GND
9
7
8
14
/R S T
CE
SCLK
DATA
43
81
HD64F2357(IC1)
E05B59(IC2)
2456
/R S T
36
E05B60(IC3)
252627
TCE
TCLK
TDATA
RTC 9810(IC8)
/R S T
/R S T
LB1847(IC11)
2
13
VREF1
VREF2
3.0 V
2
13
M 62383(IC 17)
12
/R S T
D/Axx
D/Ayx
D/Axy
3
4
8
LB1847(IC12)
VREF1
VREF2
A3957(IC13)
REF
A3957(IC14)
REF
3
3
Devision
Drops to 35 V
