SED1565 Datasheet, PDF (44/87 Pages) Epson Company – Direct display of RAM data through the display data RAM

SED1565 Series
(B) When an External Resistance is Used
(i.e., The V5 Voltage Regulator Internal
Resistors Are Not Used) (1)
The liquid crystal power supply voltage V5 can also be
set without using the V5 voltage regulator internal
resistors (IRS terminal = “L”) by adding resistors Ra’
and Rb’ between VDD and VR, and between VR and V5,
respectively. When this is done, the use of the electronic
volume function makes it possible to adjust the brightness
of the liquid crystal display by controlling the liquid
crystal power supply voltage V5 through commands.
In the range where | V5 | < | VOUT |, the V5 voltage can
be calculated using equation B-1 based on the external
resistances Ra’ and Rb’.
V₅
=
_{1 +}
Rb'
Ra'


⋅ V_EV
=
_{1 +}
Rb'
Ra'


⋅ ^1 –
α
162 ^
⋅ V_REG
[ ^{( )} ] ^QVEV ^{= 1 − α} 162 ^{⋅ V}REG
( Equation B-1)
External
resistor Ra'
VDD
VEV (fixed voltage power supply + electronic volume)
+
V5
–
External
resistor Rb'
Figure 20
Setup example: When selecting Ta = 25°C and V5 = –
7 V for an SED1567 Series model where the temperature
gradient = –0.05%/°C.
When the central value of the electron volume register
is (D5, D4, D3, D2, D1, D0) = (1, 0, 0, 0, 0, 0), then α
= 31 and VREG = –2.1 V so, according to equation B-1,
Consequently, by equations B-2 and B-3,
Rb' _{= 3.12}
Ra'
Ra' = 340kΩ
Rb' = 1060kΩ
V₅
=
_{1 +}
Rb'
Ra'


⋅1 −
α
162 ^
⋅ V_REG
−11V
=
_{1 +}
Rb'
Ra'


⋅1 −
31 
162 ^
⋅ (−2.1)
(Equation B-2)
Moreover, when the value of the current running through
Ra’ and Rb’ is set to 5 µA,
Ra' +Rb' = 1.4MΩ
(Equation B-3)
At this time, the V5 voltage variable range and notch
width, based on the electron volume function, is as
given in Table 14.
V5
Variable Range
Notch width
Min
–8.6 (63 levels)
Table 14
Typ
Max
–7.0 (central value) –5.3 (0 level)
52
Units
[V]
[mV]
8–42
EPSON