ST7567 View Datasheet(PDF) - Unspecified
Part Name
Description
MFG CO.
'ST7567' PDF : 73 Pages View PDF
ST7565S
(C) When External Resistors are Used (The V5 Voltage Regulator Internal Resistors Are Not Used) (2)
When the external resistor described above are used, adding
a variable resistor as well makes it possible to perform fine
adjustments on Ra’ and Rb’, to set the liquid crystal drive
voltage V5. In this case, the use of the electronic volume
function makes it possible to control the liquid crystal power
supply voltage V5 by commands to adjust the liquid
crystal display brightness.
In the range where | V5 | < | VOUT | the V5 voltage can be
calculated by equation C-1 below based on the R1 and R2
(variable resistor) and R3 settings, where R2 can
be subjected to fine adjustments (Δ R2).
( ) V5 =
1
+
R3+R2-ΔR2
R1+ΔR2
VEV
( ) ( ) =
1
+
R3+R2-ΔR2
R1+ΔR2
1-
α
162
VREG
[ ( ) ] ∵ VEV =
1-
α
162
VREG
VDD
Ra'
External
resistor R1
VEV(fixed voltage power supply+electronic volume)
External
ΔR2
V5
resistor R2
VR
External
Rb'
resistor R3
Figure 12
Setup example: When selecting Ta = 25°C and V5 = –5 to –9
V (using R2) for an ST7565S the temperature gradient
= –0.05%/°C.
When the central value for the electronic volume register is
set at (D5, D4, D3, D2, D1, D0) = (1, 0, 0, 0, 0, 0), then α =
31 and VREG = –2.1 V so, according to equation C-1, when Δ
R2 = 0 Ω, in order to make V5 = –9 V,
( ) ( ) -9V=
1+
R3+R2
R1
1-
31
162
(-2.1)
When ΔR2 = R2, in order to make V = –5 V,
( ) ( ) -5V=
1+
R3
R1+R2
1-
31
162
(-2.1)
With this, according to equation C-2, C-3 and C-4,
R1 = 264kΩ
R2 = 211kΩ
R3 = 925kΩ
The V5 voltage variable range and notch width based on the
electron volume function is as shown in Table 15.
When the current flowing VDD and V5 is set to 5 uA,
Table 15
V5
Min
Typ
Max
Units
Variable Range
Notch width
–8.7 (63 levels)
–7.0 (central value)
53
–5.3 (0 level)
[V]
[mV]
Ver 0.3c
37/72
2002/07/22
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