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Why negative voltage on old character LCDs?

Posted: Thu Jun 27, 2019 8:37 pm
by Megacircuits
Why did the old character LCDs have a negative voltage?

Re: Why negative voltage on old character LCDs?

Posted: Sun Jul 21, 2019 1:25 am
by focus
Older character, segment and monochrome graphic displays required a negative voltage to deal with temperature swings. More power is required to drive a monochrome display as the temperature drops.

Newer character displays have a built in circuit with a charge pump (bump circuit) the increases the output voltage necessary to keep the display active.