ST7567 View Datasheet(PDF) - Unspecified
Part Name
Description
MFG CO.
'ST7567' PDF : 73 Pages View PDF
ST7565S
(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'
VDD
VEV(fixed voltage power supply+electronic volume)
V5
External
resistor Rb'
Figure 11
Setup example: When selecting Ta = 25°C and V5 = –7 V for
ST7565S 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 = –2.1V so, according to equation B-1,
( ) ( ) V5 =
1+
Rb'
Ra'
1
-
α
162
VREG
( ) ( ) -7V=
1+
Rb'
Ra'
1
-
31
162
(-2.1)
Moreover, when the value of the current running through
Ra’ and Rb’ is set to 5 uA,
Rb'
Ra'
= 3.12
Ra' = 340kΩ
Rb' = 1060kΩ
At this time, the V5 voltage variable range and notch
width, based on the electron volume function, is as
given in Table 14.
Consequently, by equations B-2 and B-3,
V5
Variable Range
Notch width
Min
–8.6 (63 levels)
Table 14
Typ
–7.0 (central value)
52
Max
–5.3 (0 level)
Units
[V]
[mV]
Ver 0.3c
36/73
2002/07/22
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