4 POWER SUPPLY
4-2
EPSON
S1C17704 TECHNICAL MANUAL
4.2 Internal Power Supply Circuit
The S1C17704 has a built-in power supply circuit shown in Figure 4.2.1 to generate all the power voltages required
for the internal circuits. The power supply module consists of three circuits.
Table 4.2.1 Power Supply Circuit
Circuit
Power supply circuit
Output voltage
Oscillator and internal logic circuits Internal logic voltage regulator
V
D1
LCD system voltage regulator
Power voltage booster
V
DD
or V
D2
LCD driver
LCD system voltage regulator
V
C1
to V
C5
V
D1
V
D2
V
DD
External
power
supply
Oscillation circuit
Internal logic
voltage regulator
Power voltage booster
VD1MD
PBON
Internal circuit
OSC1, OSC2
OSC3, OSC4
V
DD
V
D1
V
D2
CF
CG
V
C1
V
C2
V
C3
V
C4
V
C5
CA
CB
CC
CD
CE
V
SS
LCD driver
COM0–COM31
SEG0–SEG55
VDSEL
HVLD
LCD system
voltage regulator
V
C1
~V
C5
LHVLD
Figure 4.2.1 Configuration of Power Supply Circuit
Note
: Be sure to avoid using the V
D1
, V
D2
, and V
C1
–V
C5
pin outputs to drive external circuits.
Internal logic voltage regulator
The internal logic voltage regulator generates the V
D1
operating voltage for the internal logic circuits and
oscillators. The V
D1
voltage value can be switched in the program; set it to 1.8 V for normal operation and 2.5
V for Flash programming.
Power voltage booster
The power voltage booster generates the V
D2
operating voltage for the LCD system voltage regulator. Either
V
DD
or V
D2
can be selected as the power source for the LCD system voltage regulator according to the V
DD
supply voltage value.
Table 4.2.2 Power Source for LCD System Voltage Regulator
Power supply voltage V
DD
Power source for the LCD system voltage regulator
1.8 to 2.5 V
V
D2
(
≅
V
DD
×
2)
2.5 to 3.6 V
V
DD
LCD system voltage regulator
The LCD system voltage regulator generates the 1/5-bias LCD drive voltages V
C1
, V
C2
, V
C3
, V
C4
, and V
C5
.
In the S1C17704, the LCD drive voltage is supplied to the built-in LCD driver that drives the LCD panel
connected to the SEG and COM pins.
Note
: If V
DD
is used as the power source for the LCD system voltage regulator when V
DD
is 2.5 V or
less, the V
C1
to V
C5
voltages cannot be generated within the specifications.
Содержание S1C17704
Страница 1: ...TECHNICAL MANUAL S1C17704 CMOS 16 BIT SINGLE CHIP MICROCOMPUTER ...
Страница 22: ...1 OVERVIEW 1 10 EPSON S1C17704 TECHNICAL MANUAL THIS PAGE IS BLANK ...
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