A/D Converter Circuit - Epson LQ-510 Technical Manual

PRINCIPLES OF OPERATION

2.3.7 A/D CONVERTER CIRCUIT

Figure 2-68 shows the A/D converter circuit. The functions of this converter are as follows:
Monitors the +24 V line to determine the drive pulse width for the printhead.
l
Reads the initial DIP switch settings.
l
Reads value of the setting of the bidirectional adjustment (DIP switches).
l
Reads the control panel switches.
l
The circuit's reference voltage
2.5 v
VREF =
R45
NOTE: The shunt regulator reference voltage value is 2.5 V.
With this voltage serving as the reference, the +24 V line is monitored by AN6, the head temperature is
monitored by AN7, and the DIP switches, bidirectional adjustment (DIP switches), and control panel switches
are read using AN0 through AN5.
2-60
is set, based on shunt regulator TL431 CLPB, R44, and R45, as follows:
V
REF
(R45 + R44) = 4.5 V
REV.-A
LQ-510