Epson S1D16000 Series, Technical Manual

Page: 36 / 86

S1D16400 Series
2–12
EPSON
10. REGARDING THE LCD DRIVING POWER
Methods to obtain necessary voltage levels
In order to obtain necessary voltage levels for driving of the LCD, it should be the best to divide the potential
between V
5
V
DD
resistively to drive by means of the voltage follower by the operation amplifier. In
consideration of the case of using the operation amplifier, the maximum potential level V
0
and V
DD
should
be separated to independent terminals.
Nevertheless, if V
0
potential drops below the V
DD
potential increasing the potential difference, the capacity
of the LCD driver decreases and, therefore, it is suggested that the potential difference between V0
~
V
DD
be
maintained within 0V
~
2.5V. When the operation amplifier is not used, V
0
and V
DD
should be connected.
As shown in the example of the connection, when using the resistive divider, set the resistance as low as the
power capacity of the system allows.
When a series resistance exist in the power line of V
5
(V
DD
), voltage drop of V
5
(V
DD
) at the LSI current end
occurs by I5 at times of signal changes and it becomes unable to maintain the relations of the LCD with
intermediate potentials (V
DD
>
= V
0
>
= V
2
>
= V
3
>
= V
5
) leading to breakage of the LSI. When installing protective
resistors, it is necessary to stabilize the voltage by their capacity.
Cautions when turning the power on and off
Since the LCD drive system voltage with this LSI is comparatively high, when high voltage is applied to the
LCD drive system leaving the logic power floating or leaving V
SS
= –2.6V or over or if LCD drive signals
are output before the applied voltage to the LCD drive system is stabilized, excess current may flow to break
the LSI. It therefore is suggested to bring the potential of the LCD drive output to the V
0
level until the LCD
drive system voltage gets stabilized using the display-off function (
DSPOFF
).
When turning the power on or off, follow the sequence below.
When turning on the power.....Logic systems ON
→
LCD drive system ON
(or turn them on simultaneously).
When turning off the power.....LCD drive system OFF
→
Logic system OFF
(or turn them off simultaneously).
Insert quick melting fuse in series to the LCD power source for prevention of an excess current flow.
It is necessary to choose the optimum value for the protective resistance matching the capacity of the liquid
crystal cells.
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