Specifications
SED1220
EPSON 4–17
SED1220
● Voltage Regulation Circuit Using Electronic Volume
Function
The electronic volume function allows to control the
liquid crystal drive voltage V
5 with the commands and
thus to adjust density of the liquid crystal display.
Liquid crystal drive voltage V
5 can have one of 32
voltage values if 5-bit data is set to the electronic volume
register.
[Sample constants setting when electronic volume function is used]
V
5
= (1 +
R
b
) • V
EV
...............................
2
Ra
Where VEV = VREG – α
α = V
REG / 150
When using the electronic volume function, you need to
turn the voltage regulation circuit on using the supply
control command.
R
a
R
b
V
R
V
0
V
EV
V
DD
V
REG
+
-
V
5
0
α
α
n
. . . .
No. Electronic volume register a V5
0 (0, 0, 0, 0, 0) 0 Large
1 (0, 0, 0, 0, 1) 1α •
2 (0, 0, 0, 1, 0) 2α •
3 (0, 0, 0, 1, 1) 3α •
•• ••
•• ••
30 (1, 1, 1, 1, 0) (n-1)α •
31 (1, 1, 1, 1, 1) nα Small
When the electronic volume function is not used, select (0, 0, 0, 0, 0) for the electronic volume register.