ST7565 Datasheet, PDF (26/56 Pages) Sitronix Technology Co., Ltd. – 65 x 132 Dot Matrix LCD Controller/Driver

ST7565
(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 ( R2).
Figure 12
Setup example: When selecting Ta = 25°C and V5 = –5 to –9
V (using R2) for an ST7565-0A the temperature gradient
= –0.15%/°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 =
31 and VREG = –2.1 V so, according to equation C-1, when
R2 = 0 , in order to make V5 = –9 V,
When the current flowing VDD and V5 is set to 5 uA,
With this, according to equation C-2, C-3 and C-4,
When R2 = R2, in order to make V = –5 V,
V5
Variable Range
Notch width
Min
–8.7 (63 levels)
The V5 voltage variable range and notch width based on the
electron volume function is as shown in Table 15.
Table 15
Typ
–7.0 (central value)
53
Max
–5.3 (0 level)
Units
[V]
[mV]
Ver 1.0a
26/56
2002/06/24