S1C88650 TECHNICAL MANUAL EPSON 7
2 POWER SUPPLY
2POWER 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 VDD (+)
and VSS (GND), all the voltages needed for the
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
Oscillation circuits,
Internal circuits
LCD system voltage
regulator
LCD driver
Power supply circuit
Internal logic
voltage regulator
Power voltage
booster
LCD system voltage
regulator
Output voltage
VD1
VDD or VD2
VC1–VC5
The internal logic voltage regulator generates the
operating voltage <VD1> for driving the internal
logic circuits and the oscillation circuit.
The VD1 voltage value is fixed at 1.8 V (Typ.).
The power voltage booster generates the operating
voltage <V
D2> for the LCD system voltage
regulator.
Either <V
DD> or <VD2> can be selected as the
power source for the LCD system voltage regulator
according to the <VDD> power supply voltage
level.
Table 2.2.2 Power source for LCD system
voltage regulator
Supply voltage
VDD
1.8–2.5 V
2.5–3.6 V
Power source for
LCD system voltage regulator
VD2
VDD
The VD2 voltage is about double the VDD voltage
level. Refer to Chapter 8, "ELECTRICAL
CHARACTERISTICS", for details.
The LCD system voltage regulator generates the 1/
5-bias LCD drive voltages <VC1>, <VC2>, <VC3>,
<VC4> and <VC5>. See Chapter 8, "ELECTRICAL
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 VD1,VD2,
VC1, VC2, VC3, VC4 and VC5, terminal
output be used to drive external circuit.
• If VDD is used as the power source for the
LCD system voltage regulator when VDD is
2.5 V or less, the VC1 to VC5 voltages
cannot be generated within specifications.
VDD
VD1
VD2
CF
CG
V
C1
VC2
VC3
VC4
VC5
CA
CB
CC
CD
CE
V
SS
Internal logic
voltage regulator
LCD system
voltage regulator
Oscillation circuit
LCD driver
VD1
VC1–VC5
Power
voltage
booster
External
power
supply
OSC1, OSC2
OSC3, OSC4
COM0–COM31
SEG0–SEG125
Internal circuit
VD2
Fig. 2.2.1 Configuration of power supply circuit
