ST7528 Sitronix, ST7528 Datasheet - Page 40

• Manufacturer Part Number: ST7528
• Description: 16 Gray Scale Dot Matrix LCD Controller
• Manufacturer: Sitronix

ST7528
Voltage Converter Circuits
These circuits boost up the electric potential between VDD2 and Vss to 3, 4, 5 or 6 times toward positive side and boosted
voltage is outputted from VOUT pin. It is possible to select the lower boosting level in any boosting circuit by “Set DC-DC
Step-up” instruction. When the higher level is selected by instruction, VOUT voltage is not valid.
Note: we would like to recommend to use the external VOUT when the panel is large than 1.8 inch
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 16, 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
instruction, "Set Reference Voltage Register", within the range 0 to 63. VREF voltage at Ta= 25 C is shown in Table 5.
V0 = (1 +
VEV = (1 -
REF
1
0
Ver2.3
Rb
Ra
(63 - )
210
) x VEV [V] ------ (Eq. 1)
) x VREF [V] ------ (Eq. 2)
V
EV
Figure 16 Internal Voltage Regulator Circuit
Temp. coefficient
-0.125% / C
External input
Table 5 VREF Voltage at Ta = 25°C
40/97
+
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VOUT
VREF [ V ]
2.1
VEXT
GND
VSS
V0
Rb
VR
Ra
is the value selected by
2007/1/3
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