• We recently switched our forum platform. If you experience any issues please email support@crystalfontz.com

CFAG12864B-TMI-V Backlight Specifications

eric_v

New member
The datasheet for the CFAG12864B-TMI-V appears to have conflicting information on the backlight specification.

On page 17 it lists the maximum voltage as 3.7V and maximum current as 90ma@3.5V.

On page 8 it shows some drive methods for the backlight. There under recomended values it lists VLED as 4.1V and ILED as 100ma. Both of these are beyond the maximums listed for the backlight.

I did find one other post from november 2003 regarding this, but the response was inadaquate. If this has been known for this long, why do you not fix your datasheets?

Eric V
Looking for additional LCD resources? Check out our LCD blog for the latest developments in LCD technology.
 
Apparently not.

You should email tech support and/or sales if you want a response, but I wouldn't hold my breath for a speedy data sheet update.

Meanwhile, just use the more conservative ratings. You can do a little experimenting to see how hot the backlight gets at higher current (and shorter lifetime).
 

eric_v

New member
Since we use a number of these LCDs in variouse projects, i was just looking to get some kind of definitive answer. I have seen a few people having issues with them, blown two up completly from over driving the backlight. The lower values seem correct, and i have had no problems at thoes levels.

I know many data sheets have errors in them, but most are corrected through either updates to the data sheets or erratas.

It just feels kind of underhanded when the data sheet gives a recomended driver that kills the LCD. I begin to wonder if they dont bother changing the data sheets so they can sell more LCDS once hobbyists, and CS students blow them up. I doubt this would account for a lot of buisness but one has to ask.

We have not had any trouble using the character LCDs, and have been using thoes for years. This year has been the first use of the graphic ones. We have also had trouble with the EL backlight specs seeming to be way off as well. If this is how all the graphic LCDs are I guess i will have to start recomending a diferent supplier.
 

JRG

New member
Hey Eric,

I have the same display, did some testing:

I supplied 5.05V to pin 19 thru a 100ohm pot. I set the pot until the display looked OK (brightness), measured the pot at 14.8 ohm and the current thru the LED at 65mA.

At 5.05V supplied, that gives the LED a volt drop of 4.088V.

This number seems to indicate the values given in the LED hookup examples on page 8 of the data sheet are probably correct. I am going to use a 12 ohm resistor to set the current at about 80mA ... should be OK.
 
Top