ST7533 datasheet(22/60 Pages) SITRONIX

22 / 60 page

ST7533

Ver 1.0

22/60

2003/07/21

The Voltage Regulator Circuit

The step-up voltage generated at VOUT outputs the LCD

driver voltage V5 through the voltage regulator circuit.

Because the ST7533 chips have an internal high-accuracy

fixed voltage power supply with a 64-level electronic volume

function and internal resistors for the V5 voltage regulator,

systems can be constructed without having to include

high-accuracy voltage regulator circuit components.

(VREG thermal gradients approximate -0.15%/°C)

(A) When the V5 Voltage Regulator Internal Resistors Are Used

Through the use of the V5 voltage regulator internal resistors

and the electronic volume function the liquid crystal power

supply voltage V5 can be controlled by commands alone

(without adding any external resistors), making it possible to

adjust the liquid crystal display brightness. The V5 voltage

can be calculated using equation A-1 over the range where

| V5 | < | VOUT |.

Figure 8

()

VEV

V5 =

()

(1-

162 )

VREG

[∵VEV = (1-

162 )

VREG

]

Internal Ra

Internal Rb

VEV(constant voltage supply+electronic volume)

VDD

ST7533 Datasheet(PDF) 22 Page - Sitronix Technology Co., Ltd.