ST7565R datasheet(33/72 Pages) SITRONIX

33 / 72 page

ST7565R

Ver 1.7c

33/72

2009/09/14

The Voltage Regulator Circuit

The step-up voltage generated at VOUT outputs the LCD

driver voltage V0 through the voltage regulator circuit.

Because the ST7565R chips have an internal high-accuracy

fixed voltage power supply with a 64-level electronic volume

function and internal resistors for the V0 voltage regulator,

systems can be constructed without having to include

high-accuracy voltage regulator circuit components.

(VREG thermal gradients approximate -0.05%/°C)

(A) When the V0 Voltage Regulator Internal Resistors Are Used

Through the use of the V0 voltage regulator internal resistors

and the electronic volume function the liquid crystal power

supply voltage V0 can be controlled by commands alone

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

adjust the liquid crystal display brightness. The V0 voltage

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

| V0 | < | VOUT |.

(

)

VEV

V0 =

(

)

(1 -

162)

VREG

[∵ VEV = (1 -

162)

VREG

]

Internal Ra

VEV(constant voltage supply+electronic volume)

VSS

Internal Rb

Figure 8

VREG is the IC-internal fixed voltage supply, and its voltage at Ta = 25°C is as shown in Table 9.

Table 9

Part no.

Equipment Type

Thermal Gradient

VREG

ST7565R

Internal Power Supply

–0.05 %/°C

2.1V

α is set to 1 level of 64 possible levels by the electronic volume function depending on the data set in the 6-bit electronic

volume registers. Table 10 shows the value for α depending on the electronic volume register settings.

Rb/Ra is the V0 voltage regulator internal resistor ratio, and can be set to 8 different levels through the V0 voltage regulator

internal resistor ratio set command. The (1 + Rb/Ra) ratio assumes the values shown in Table 11 depending on the 3-bit data

settings in the V0 voltage regulator internal resistor ratio register.

ST7565R Datasheet(PDF) 33 Page - Sitronix Technology Co., Ltd.

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