HM17CM256 datasheet(45/111 Pages) HYNIX

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HM17CM256

- 45 -

(31) SUPPLYING POWER AND ON/OFF SEQUENCE

Special care should be taken to the next notice. Supplying the power at LCD driving voltage

terminal when the logic VDD is floating can cause over-current and damage the IC

(31-1) WHEN USING EXTERNAL POWER SUPPLY

power ON sequence

Reset the IC after supplying the logic power at VDD terminal, and then turn on the LCD driving

voltage at the terminals (VLCD, V1, V2, V3, V4).

And when internal voltage converter is used, reset the IC after supplying the logic power at

VDD terminal, and then supply power to VLCD terminal.

power OFF sequence

Execute HALT command or reset the IC to turn off the outputs of LCD driving output port, and

then turn off the LCD driving voltage after logic power OFF.

Inserting series resistor of 50 ~100

Ω or fuse at V

LCD or VOUT terminal (when only internal

voltage converting circuit is used) is recommended to prevent over-current.

This series resistor should be selected carefully because image quality can be dependent on.

(31-2) WHEN USING BUILT-IN POWER SUPPLY CIRCUIT

power ON sequence

Reset the IC after supplying the logic power at VDD terminal or after supplying power through

voltage common port (VEE) of boosting voltage generation and then operate internal power

circuit by command.

And when internal voltage converter is used, reset the IC after supplying the logic power at

VDD terminal, and then supply power to VLCD terminal.

You should turn on the display after the output level of internal power module is set.

If you do not keep this sequence, LCD can display wrong data.

power OFF sequence

To make off state of LCD driving output, cut the source to voltage common port (VEE) of

boosting voltage generation, the logic power at VDD terminal after reset the IC by HALT

command.

If VEE, and VDD are supplied from different power source, VEE terminal should be turned on/off

during VDD terminal voltage maintain voltage level specified in specification sheet.

Specially, when turn off the power, after cut the source to voltage common port (VEE), and then

turn off the logic power at VDD terminal after the voltage levels of VEE, VOUT, VLCD, V1~V4 become

under LCD on voltage(LCD threshold voltage)level.

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