Specifications
EPSON 7–15
SED1234/35 Series
SED1234/35
Series
Liquid crystal voltage generating circuit
The V
5 potential is resistance-divided inside the IC so
that V
1, V2, V3 and V4 potentials are generated for liquid
crystal drive.
Furthermore, the V
1, V2, V3 and V4 are impedance-
converted by voltage follower and the then supplied to
the liquid crystal drive circuit.
The liquid crystal drive voltage is fixed to 1/5 bias.
As shown in the diagrams below, the capacitor (C2) for
voltage stabilization must be externally connected to the
V
1 to V5 pins of liquid crystal power pins.
V1
V2
V3
V4
V5
External
power
supply
SED123✽D✽✽
VDD
V5
VR
CAP1+
CAP1–
CAP2+
CAP2–
V
OUT
VSS
When a built-in power supply is not used
Reference setting values: C1: 0.1 - 4.7 µF
C2: 0.1 µF
We recommend the user to set the optimum values to capacitors C1
and C2 according to the panel size watching the liquid crystal display
and drive waveforms.
When a built-in power supply is used
Under a triple boosting
CAP1+
CAP1–
V
OUT
V
5
R3
R2
R1
V
DD
, V
0
C2
V
1
V
2
V
3
V
4
V
5
V
R
V
SS
SED123✽D
✽✽
C1
C1
CAP2+
CAP2–
C1
The diagram under a double boosting
CAP1+
CAP1–
V
OUT
V
5
R3
R2
R1
V
DD
, V
0
C2
V
1
V
2
V
3
V
4
V
5
V
R
V
SS
SED123✽D✽✽
C1
CAP2–
CAP2+
C1
When an external power regulator is used
(The built-in power regulator is not used)
CAP1+
CAP1–
V
OUT
V
5
V
DD
, V
0
C2
V
1
V
2
V
3
V
4
V
5
V
R
V
SS
SED123✽D
✽✽
C1
C1
CAP2+
CAP2–
C1
External
power
regulator