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2 POWER SUPPLY
In this section, we will explain the operating voltage and the configuration of the internal power
supply circuit of the S1C88650.
2.1 Operating Voltage
The S1C88650 operating power voltage is as
follows:
1.8 V to 3.6 V
2.2 Internal Power Supply Circuit
The S1C88650 incorporates the power supply
circuit shown in Figure 2.2.1. When voltage within
the range described above is supplied to V
and V
(GND), all the voltages needed for the
SS
internal circuit are generated internally in the IC.
Roughly speaking, the power supply circuit is
divided into three sections.
Table 2.2.1 Power supply circuit
Circuit
Power supply circuit
Oscillation circuits,
Internal logic
Internal circuits
voltage regulator
LCD system voltage
Power voltage
regulator
booster
LCD driver
LCD system voltage
regulator
The internal logic voltage regulator generates the
operating voltage <V
D1
logic circuits and the oscillation circuit.
The V
voltage value is fixed at 1.8 V (Typ.).
D1
The power voltage booster generates the operating
voltage <V
> for the LCD system voltage
D2
regulator.
External
power
supply
S1C88650 TECHNICAL MANUAL
(+)
DD
Output voltage
V
D1
V
V
or
DD
D2
V
V
–
C1
C5
> for driving the internal
V
DD
Internal logic
V
D1
voltage regulator
V
D2
CF
Power voltage
CG
booster
V
V
C1
V
C2
V
C3
V
C4
LCD system
V
C5
voltage regulator
CA
CB
CC
CD
CE
V
SS
Fig. 2.2.1 Configuration of power supply circuit
Either <V
> or <V
DD
power source for the LCD system voltage regulator
according to the <V
level.
Table 2.2.2 Power source for LCD system
Supply voltage
V
DD
1.8–2.5 V
2.5–3.6 V
The V
voltage is about double the V
D2
level. Refer to Chapter 8, "ELECTRICAL
CHARACTERISTICS", for details.
The LCD system voltage regulator generates the 1/
5-bias LCD drive voltages <V
<V
> and <V
C4
C5
CHARACTERISTICS" for the voltage values.
In the S1C88650, the LCD drive voltage is supplied
to the built-in LCD driver which drives the LCD
panel connected to the SEG and COM terminals.
Notes: • Under no circumstances should V
V
, V
C1
output be used to drive external circuit.
• If V
DD
LCD system voltage regulator when V
2.5 V or less, the V
cannot be generated within specifications.
Oscillation circuit
V
D1
Internal circuit
D2
V
V
C1–
C5
LCD driver
EPSON
2 POWER SUPPLY
> can be selected as the
D2
> power supply voltage
DD
voltage regulator
Power source for
LCD system voltage regulator
V
D2
V
DD
DD
>, <V
C1
C2
>. See Chapter 8, "ELECTRICAL
, V
, V
and V
, terminal
C2
C3
C4
C5
is used as the power source for the
to V
voltages
C1
C5
OSC1, OSC2
OSC3, OSC4
COM0–COM31
SEG0–SEG125
voltage
>, <V
>,
C3
,V
,
D1
D2
is
DD
7
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