Specifications
EPSON 8–19
SED1240 Series
SED1240
Series
Liquid crystal voltage generating circuit
The V
5 potential is resistance-divided by the built-in
resistor of the IC or external resistors Ra and Rb,
generating potentials V
1, V2, V3, and V4 required for
liquid crystal drive. Furthermore, potentials V
1, V2, V3,
and V
4 are impedance-converted by the voltage follower
and supplied to the liquid crystal drive circuit.
Regarding the liquid crystal drive voltage, the 1/5 bias or
1/4 bias can be selected by command. For liquid crystal
power pins, capacitors C2 for voltage stabilization must
be connected to pins V
1 to V5 externally.
A reference circuit example of each case is shown below.
CAP1+
CAP1–
V
OUT
V
5
V
DD
, V
0
C
2
C
2
C
2
C
2
C
2
V
1
V
2
V
3
V
4
V
5
V
S1
V
R
V
SS
V
SS2
SED124XD
XX
C
1
C
1
CAP2–
CAP2+
C
1
[When using a V
5
voltage regulating built-in resistor]
(Example of V
SS2
= V
SS
, triple boosting)
CAP1+
CAP1–
V
OUT
V
5
R
3
R
2
R
1
V
DD
, V
0
C
2
C
2
C
2
C
2
C
2
V
1
V
2
V
3
V
4
V
5
V
S1
V
R
V
SS
V
SS2
SED124XD
XX
C
1
C
1
CAP2–
CAP2+
C
1
[When using no V
5
voltage regulating built-in resistor]
(Example of V
SS2
= V
SS
, triple boosting)
CAP1+
CAP1–
V
OUT
V
5
V
DD
, V
0
C
2
C
2
C
2
C
2
C
2
V
1
V
2
V
3
V
4
V
5
V
S1
V
R
V
SS
V
SS2
SED124XD
XX
C
1
CAP2–
CAP2+
C
1
(Example of V
SS2
= V
SS
, double boosting)
CAP1+
CAP1–
V
OUT
V
5
R
3
R
2
R
1
V
DD
, V
0
C
2
C
2
C
2
C
2
C
2
V
1
V
2
V
3
V
4
V
5
V
S1
V
R
V
SS
V
SS2
SED124XD
XX
C
1
CAP2–
CAP2+
C
1
(Example of V
SS2
= V
SS
, double boosting)
1 Using all of the boosting circuit, power regulating circuit, and voltage follower
Reference set values: C1: 0.47 to 4.7 µF It is recommended to set optimum values suitable for the panel size in
C2: 0.1 to 4.7 µF capacitors C1 and C2 while watching the liquid crystal display and drive
waveforms.