S6B0755 Datasheet, PDF (30/68 Pages) Samsung semiconductor – 128 SEG / 65 COM DRIVER & CONTROLLER FOR STN LCD

S6B0755
PRELIMINARY SPEC. VER. 1.0
128 SEG / 65 COM DRIVER & CONTROLLER FOR STN LCD
Voltage Regulator Circuits
The function of the internal Voltage Regulator circuits is to determine liquid crystal operating voltage, V0, by
adjusting resistors, Ra and Rb, within the range of |V0| < |VOUT|. Because VOUT is the operating voltage of
operational-amplifier circuits shown in Figure 20, it is necessary to be applied internally or externally.
For the Eq. 1, we determine V0 by Ra, Rb and VEV. The Ra and Rb are connected internally or externally by
INTRS pin. And VEV called the voltage of electronic volume is determined by Eq. 2, where the parameter α is the
value selected by instruction, "Set Reference Voltage Register", within the range 0 to 63. VREF voltage at Ta=
25°C is shown in Table 10.
Rb
V0 = (1 +  ) x VEV [V] ------ (Eq. 1)
Ra
(63 - α)
VEV = (1 -  ) x VREF [V] ------ (Eq. 2)
210
REF
1
0
Table 10. . VREF Voltage at Ta = 25°C
Temp. coefficient
-0.05% / °C
External input
VREF [ V ]
2.1
VEXT
VOUT
+
-
V EV
V0
Rb
VR
Ra
VSS
GND
Figure 20. Internal Voltage Regulator Circuit
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