HM17CM256 datasheet(39/111 Pages) HYNIX

39 / 111 page

HM17CM256

- 39 -

(24) ELECTRIC VOLUME

The electric volume is within voltage converting circuit and the brightness of LCD can be controlled

by adjusting VLCD level with command.

The LCD driving voltage VLCD is generated by selecting 1 level within 128 step electric volume

controlled levels by setting 7 bit electric volume register.

(25)

VOLTAGE REGULATOR CIRCUIT

The voltage regulator circuit is within voltage converting circuit and generates regulated voltage

using VREF input with magnification by adjusting internal resistor.

The generated voltage by voltage

regulator is output at VREG terminal.

Even though boosted voltage variation, generated regulator

voltage is stable because boosting voltage level is higher than the amplified regulator voltage VREG .

And so, stable voltage level can be generated even if there is load variation.

VREG is used as input voltage of electric volume circuit to generate LCD driving voltage.

(26) REFERENCE VOLTAGE GENERATION CIRCUIT

The reference voltage generation circuit is within voltage converting circuit.

This circuit generates reference voltage VBA terminal for using at regulator circuit through.

The

output voltage level from VBA terminal is as following description.

VBA = VEE x 0.9

The LCD driving voltages can be made by applying reference voltage to reference voltage input

terminal VREF .

(27)

LCD DRIVING VOLTAGE GENERATION CIRCUIT

The generation circuit of LCD driving voltage is within voltage converting circuit and generates

voltages VLCD, V1, V2, V3, V4 by resistively dividing VLCD into 4 levels.

The bias ratio of LCD driving voltages can be one of 1/5, 1/6, 1/7, 1/8, 1/9, 1/10.

When using built-in power supply circuit, you should connect voltage stabilization capacitor CA2 at

each of LCD power terminals.

There is need for selecting the coefficient of capacitor CA2 after

display the LCD.

When using external voltage supply, disable the built-in power supply circuit(AMPON, DCON=‘00’),

supply the VOUT, VLCD, V1, V2, V3, V4 voltages externally and open the C1+ , C1- , C2+ , C2- , C3+ , C3- ,

C4+ , C4- , C5+ , C5- , C6+ , C6- , VEE , VREF , VREG terminals.

When using external voltage source and parts of built-in voltage converting circuit, the terminals of

C1+ , C1- , C2+ , C2- , C3+ , C3- , C4+ , C4- , C5+ , C5- , C6+ , C6- should be open because boosting

circuit is not activated, you should supply reference voltage through VREF terminal and the voltage for

voltage converting circuit at VOUT .

Connecting stabilization capacitor CA3 at VREG terminal is recommended.

HM17CM256 Datasheet(PDF) 39 Page - Hynix Semiconductor

HM17CM256 Datasheet(HTML) 39 Page - Hynix Semiconductor

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