ST7565 View Datasheet(PDF) - Unspecified
Part Name
Description
MFG CO.
'ST7565' PDF : 56 Pages View PDF
ST7565
(B) When an External Resistance is Used (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'
VEV
( ) ( ) =
1+
Rb'
Ra'
1-
α
162
VREG
[ ( ) ] ∵ VEV =
1-
α
162
VREG
External
resistor Ra'
External
resistor Rb'
VDD
VEV(fixed voltage power supply+electronic volume)
V5
Figure 11
Setup example: When selecting Ta = 25°C and V5 = –7 V for
ST7565-0A the temperature gradient = –0.15%/°C.
Ra'+ Rb'= 1.4MΩ
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 = –2.1V so, according to equation B-1,
Consequently, by equations B-2 and B-3,
Rb'
Ra'
= 3.12
( ) ( ) V5 =
1+
Rb'
Ra'
1-
α
162
VREG
Ra' = 340kΩ
Rb' = 1060kΩ
( ) ( ) -7V=
1+
Rb'
Ra'
1-
31
162
(-2.1)
At this time, the V5 voltage variable range and notch
width, based on the electron volume function, is as
Moreover, when the value of the current running through
given in Table 14.
Ra’ and Rb’ is set to 5 uA,
Table 14
V5
Min
Typ
Max
Units
Variable Range
Notch width
–8.6 (63 levels)
–7.0 (central value)
52
–5.3 (0 level)
[V]
[mV]
Ver 1.0a
25/56
2002/06/24
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