At 07:42 PM 2/1/2003 +0800, you wrote:
>Hi,
>
>I'm using a 20*2 LCD from CrystalFontz.com with a backlight.
>Here is the datasheet:
>http://www.crystalfontz.com/products/2002a-wt/CFAH2002AYYHJPV.pdf
>
>Anyway, in the datasheet it says teh supply current is 5mA, but doesn't say if
>it is the logic, LCD or backlight. Actually it doesn't give much
>information on the
>backlight at all.
>
>Can anyone tell me what requires only the 5mA current? Should I just put a
>resister infront of
>Vdd for logic, and one infront for the backlight? At the moment, I'm using
>a 5V supply (roughly
>5.10) from the computer which has a high current ~8A

RTFM- the LCD portion requires 5V at 5mA typical (p5), the backlight requires
210mA at 4.1V typical (p20). You do NOT put a resistor in series with the
logic, you MUST put one in series with the backlight. Since Vf of the
backlight
is not well specified and the 5V can be a bit high you had better design for
lower backlight current. Try something like a 10R 1/4 W resistor, though
5.5 ohms would be closer to the maximum brightness without cut and trim.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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