Re: [uCsimm] Motorola Dragonball ADS Board LCD

From: Tom Walsh (
Date: Thu May 18 2000 - 15:41:58 EDT


> Hi, everyone,
> Thanks for your help, I now can calculate the appropriate regesiter value
> and figure out what I should do next step. I would have to get the voltage
> boost and regulate chip LT1372HV first. I really don't know the chip
> DC0105 used by the circuit suggested by RTcontrol. Anyway, I have to build
> the circuit myself.

    Exactly, I could not find the part referenced in their circuit either, I assume it was a
PCB rather than a discrete part. You may not need the LT1372HV device, I choose it because
of the higher bias required by the Epson display exceeded the ratings of the LT1372 device.
If you are not going to need a voltage in excess of about 32volts for your display, then use
the LT1372 device, it is available thru DigiKey!

BE VERY CAREFUL when you start the circuit up, as you can see, I have a pot on the device,
make sure that the pot is set to midpoint! I destroyed two devices in determining trimming
the ratios of the resistances, they are VERY easy to damage!

> A stupid question, can I assume that the LCD in my hand is capable of
> Both Positive Bias voltage VEE and Negative VEE. Because when I check with
> ADS board manual, it says it will output Negative VEE. But when I check
> the LCD module Data sheet, it state 23V for VEE (no clear sign for + or
> -). And the worst is that I don't have the data sheet for the connector
> circuit. So I am just mixed up by the Polarity of the VEE.

Never assume. When in doubt, query the manufacturer of the module, you have to believe that
they know what their module is supposed to do / need. "Read" the schematic of the ADS
board, see what the VEE supply is capable of doing, if you are not sure, get a data sheet
on the device used on the ADS board and look for an application circuit that more closely
matches the one on the ADS board. Be aware that many switching regulators can be configured
to output either positive or negative voltages, but look at the circuits that they give you
on the data sheet.



Tom Walsh - WN3L - Embedded Systems Consultant
'', ''
"Windows? No thanks, I have work to do..."

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