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Fabricante

NT7501

33 X 100 RAM-Map LCD Controller/Driver

Novatek Microelectronics 

NT7501

Voltage Regulator Circuit

The function of the internal voltage regulator circuits is to determine the liquid crystal operating voltage V0, by adjusting resistors

Ra and Rb, within the range V0 < VOUT. VOUT is the operating voltage of the operational amplifier circuits shown in Figure 6.

Feedback gain control for initial LCD voltage. External resistors are connected between V0 and VR, and between VR and VSS

and these resistors are chosen to give the desired V0 according to the following equation:

V0 = (1 + Rb/Ra) X VREG + Rb X Iref

TPS1

0

0

1

1

TPS0

0

1

0

1

Thermal Gradient (% / °C)

-0.05 (Internal VREG used)

-0.2 (Internal VREG used)

0

0

VREG (V)

2.2

2.45

VDD

VDD

Voltage Regulator Using the Electronic Volume Control Function

The Electronic Volume Control Function can adjust the intensity (brightness level) of the LCD screen by electronic control

command.

Software controls the 32 voltage levels of V0. This yields the following equation:

V0 = (1+ Rb/Ra) X VREG + Rb X Iref

Where Iref = 0 to 6.5µA ± 40% depending on the 5-bit data set by the electronic control command.

Rb

Vout

Ra

V0

Iref

VREG

Vss

Figure 6.

14

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