8
EPSON
S1C63455 TECHNICAL MANUAL
CHAPTER 2: POWER SUPPLY AND INITIAL RESET
2.1.1 Voltage <VD1> for oscillation circuit and internal circuits
VD1 is a voltage for the oscillation circuit and the internal logic circuits, and is generated by the oscillation
system voltage regulator for stabilizing the oscillation.
The S1C63455 is designed with twin clock specification; it has two types of oscillation circuits OSC1 and
OSC3 built-in. Use OSC1 clock for normal operation, and switch it to OSC3 by the software when high-
speed operation is necessary. When switching the clock, the operating voltage VD1 must be switched by
the software to stabilize the operation of the oscillation circuit and internal circuits.
The oscillation system voltage regulator can output the following two types of VD1 voltage. It should be
set at the value according to the oscillation circuit and oscillation frequency by the software.
Single clock operation (OSC1 crystal oscillation):
VD1 = 1.3 V
Single clock operation (OSC1 CR oscillation):
VD1 = 2.2 V
Twin clock operation (OSC3, 4 MHz ceramic oscillation or 1.8 MHz CR oscillation): VD1 = 2.2 V
Refer to Section 4.3, "Oscillation Circuit", for the VD1 switching procedure.
However, since the VD1 voltage value is fixed at 2.2 V when the CR oscillation circuit has been selected as
the OSC1 oscillation circuit by mask option, it is not necessary to switch VD1 by software.
2.1.2 Voltage <VC1, VC2, VC4, VC5> for LCD driving
VC1, VC2, VC4 and VC5 are the LCD drive voltages generated by the LCD system voltage circuit. These
four output voltages can only be supplied to the externally expanded LCD driver.
The LCD system voltage circuit generates VC1 or VC2 with the voltage regulator built-in, and generates
three other voltages by boosting or reducing the voltage of VC1 or VC2. Table 2.1.2.1 shows the VC1, VC2,
VC4 and VC5 voltage values and boost/reduce status.
Table 2.1.2.1 LCD drive voltage when generated internally
LCD drive voltage
VC1 (0.975–1.2 V)
VC2 (1.950–2.4 V)
VC4 (2.925–3.6 V)
VC5 (3.900–4.8 V)
VDD = 1.8–6.4 V
VC1 (standard)
2
× VC1
3
× VC1
4
× VC1
VDD = 2.6–6.4 V
1/2
× VC2
VC2 (standard)
3/2
× VC2
2
× VC2
Note: The LCD drive voltage can be adjusted by the software (see Section 4.7.5). Values in the above
table are typical values.
Either the VC1 or VC2 used for the standard is selected according to the supply voltage by the software.
The VC2 standard improves the display quality and reduces current consumption, however, the power
supply voltage VDD must be 2.6 V or more.
Refer to Section 4.7, "LCD Driver", for control of the LCD drive voltage.