Portable CFAH


New member
I'm looking to use a CFAH2004 series display for a portable application. It's primary use will be indoors under varying lighting conditions, so I'm considering transmissive and transflective displays. I'm looking at the CFAH2004A-YYB-JPE and CFAH2004A-YYB-JP transflective display and the CFAH2004A-TMI-JP transmissive display. Since battery life is critical, I have a few questions:

1. The website http://www.crystalfontz.com/products/2004a/index.html for the first two displays says the backlight provides "Minimum 70 CD/M^2 backlight brightness at 130mA backlight current" for the CFAH2004A-YYB-JP but the data sheet says 60 CD/M^2 at 280mA. Similarly, the website says "Typical 12 CD/M2 backlight brightness at 20mA backlight current" for the CFAH2004A-YYB-JPE but the data sheet says 20 CD/M^2 backlight brightness at 100mA.

Who's right? If both are right, do I just select a resistor to match the current as desired? Is there a curve I can use to estimate these values?

2. Is there a good way to visualize the differences in brightness? For that matter, what are the current or intensity values for the pictures on the website?

3. In light of the first question, are the values of 20 CD/M^2 backlight brightness at 100mA accurate for the CFAH2004A-TMI-JP?

4. I'm leaning towards the transmissive display because of the low current requirement since the transflective backlight would be on most of the time anyway. Adding an on/off switch would probably confuse the user. Still, any comments on choice of technology would be welcome.

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CF Tech

Pleas use the data sheet for specfications. I'll ask the web people to correct the page.

For battery operation, generally you would want to use the edge-lit transflective mode. The edge-lit would be a little better on current and the transflective allows you to turn the backlight off most of the time.

If you really want to reduce your current though, something like the CFAX series would be best.