
I-8
EPSON
S1C62740 TECHNICAL HARDWARE
CHAPTER 2: POWER SUPPLY AND INITIAL RESET
VD1 is the voltage of the oscillation circuit and the internal logic
circuit, and is generated by the oscillation system regulated voltage
circuit for stabilizing the oscillation.
Making VSS the standard (logic level 0), the oscillation system
regulated voltage circuit generates VD1 from the supply voltage that
is input from the VDD–VSS terminals.
Voltage <VD1> for
oscillation circuit
and internal circuit
Voltage <VC1, VC2
and VC3> for LCD
driving
VC1, VC2 and VC3 are the voltages for LCD drive, and are generated
by the LCD system regulated voltage circuit and the voltage booster
circuit to stabilize the display quality.
VC1 is generated by the LCD system regulated voltage circuit with
VSS as the standard from the supply voltage input from the VDD–
VSS terminals.
VC2 and VC3 are respectively double and triple obtained from the
voltage booster circuit.
The VC1 voltage can be adjusted to match the LCD panel character-
istics by applying feedback to the VCA terminal using resistances
RA1 and RA2 as shown in Figure 2.1.2.
The voltage VC (
≈VC1–VSS) of VC1 at this time is shown by the
following expression:
VC
≈ 1 × (RA1 + RA2) / RA1
Example:
VC
RA1
RA2
About 1 V
∞
0
About 1.5 V
2 M
1 M
See Chapter 7, "ELECTRICAL CHARAC-
TERISTICS" for voltage values.
+
–
VC1
VCA
RA2
RA1
VSS
+
–
VC1
VCA
VSS
VC = 1.5 V
VC = 1 V
(1 M )
(2 M )
Fig. 2.1.2
VC Adjustment circuit
VR1 and VR2 are the reference voltage of the A/D converter. VR1 is
generated by the regulated voltage circuit and VR2 by resistance
splitting of VR1. VR1 and VR2 may also be adjusted from outside.
Use of the external adjustment or the internal adjustment can be
selected by the mask option. In addition, it is possible to impress
VR1 externally.
VR1 is used to generate VR2 and the reference voltage during
resistance measurement using an A/D converter and VR2 becomes
the reference voltage at the time of voltage measurement by the A/
D converter.
Reference voltage
<VR1 and VR2> for
A/D converter