5 POWeR SuPPlY
5-2
Seiko epson Corporation
S1C63003/004/008/016 TeChniCal Manual
(Rev. 1.1)
The power supply circuit is broadly divided into three blocks.
2.1 Power supply circuit
Table 5.
Power supply circuit/power supply voltage
Output
voltage
Circuits to be driven
3 V normal type
1.5 V low-voltage type
Internal operating voltage regulator
V
D1
CPU, internal circuits,
and OSC3 oscillation circuit
OSC3 oscillation circuit
OSC1 oscillation circuit voltage regulator
V
OSC
OSC1 oscillation circuit
LCD system voltage regulator
V
C1
–V
C3
LCD driver
Power supply voltage V
DD
–
Power supply circuit, and I/O
Power supply circuit, CPU,
internal circuits, and I/O
internal operating voltage regulator
This voltage regulator always operates to generate the V
D1
operating voltage for the CPU, internal logic circuits
and the OSC3 oscillation circuits.
(The CPU and internal logic circuits in the 1.5 V low-voltage type operate with the power supply voltage V
DD
.)
OSC1 oscillation circuit voltage regulator
This voltage regulator always operates to generate the V
OSC
operating voltage for the OSC1 oscillation circuit.
lCD system voltage regulator
The LCD system voltage regulator generates the LCD drive voltages V
C1
to V
C3
. See "Electrical Characteristics"
for the voltage values. In the S1C63003/004/008/016, the LCD drive voltage is supplied to the built-in LCD driver
that drives the LCD panel connected to the SEG and COM terminals.
The LCD system voltage regulator can be disabled by mask option to supply external voltages. In this case, ex-
ternal elements can be minimized because the external capacitors for the LCD system voltage regulator are not
necessary. However when the LCD system voltage regulator is not used, the display quality of the LCD panel,
when the supply voltage fluctuates (drops), is inferior to when the LCD system voltage regulator is used.
Figure 5.2.2 shows the external element configuration when an external LCD power supply is used.
V
DD
V
C1
V
C2
V
C3
CA
CB
V
SS
3.0 V
4.5 V LCD panel, 1/3 bias
3 V LCD panel, 1/3 bias
3 V LCD panel, 1/2 bias
4.5 V LCD panel, 1/3 bias
3 V LCD panel, 1/3 bias
3 V LCD panel, 1/2 bias
4.5 V LCD panel, 1/3 bias
3 V LCD panel, 1/2 bias
(3 V normal type, single power supply)
C
2
C
3
C
1
V
DD
V
C1
V
C2
V
C3
CA
CB
V
SS
3.0 V
C
2
C
3
C
1
V
DD
V
C1
V
C2
V
C3
CA
CB
V
SS
3.0 V
C
2
C
1
V
DD
V
C1
V
C2
V
C3
CA
CB
V
SS
3.0 V
1.1–
1.7 V
1.1–
1.7 V
(1.5 V low-voltage type, dual power supply)
(1.5 V low-voltage type, single power supply)
C
2
C
3
C
1
V
DD
V
C1
V
C2
V
C3
CA
CB
V
SS
C
2
C
3
C
1
V
DD
V
C1
V
C2
V
C3
CA
CB
V
SS
C
2
C
1
V
DD
V
C1
V
C2
V
C3
CA
CB
V
SS
1.5 V
C
2
C
2
C
3
C
1
V
DD
V
C1
V
C2
V
C3
CA
CB
V
SS
1.5 V
C
1
3.0 V
1.1–
1.7 V
3.0 V
2.2 External elements when an external LCD power supply is used
Figure 5.