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CFAX12864 Power Consumption Question

Altzone

New member
Hi
I'm looking at the CFAX12864A-WFH or CFAX12864AP1-NFH displays with the Samsung KS0713 controller.
My question is about the static display current consumption (i.e. displaying an image, but no screen updating).
The KS0713 datasheet shows around 70uA typical when using the charge pump, but the LCD datasheets show 1.5mA or 1mA typical rated at 5V only. I find it hard to believe the static LCD image and extra voltage would add this much.
I will be using the internal charge pump and a single 3V or 3.3V supply.

Does anyone know the actual typical operating current of these displays at around 3V?

If it is actually 1mA or so then I've blown my power budget, as I'm targeting around several hundred uA tops.

Thanks
Dave.
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I may have some good news for you. I have a project that uses the CFAX12864AP1-TFH on a 3.3 volt supply. I split the trace that feeds the 3.3 to the FPC connector, so that I could insert a VOM in series. My measurements show about 100uA to 135uA, depending on number of pixels "on". None of my screens have a high pixel "on" percentage, but I'd be surprised if the current would go over 200~250uA with a full screen, but I'm too lazy to change my code and reflash the cpu to test that out.

What is interesting is that when I break the connection to the meter, the display does not lose the image, indicating that the power is being supplied by leakage currents thru the 5v-to-3.3v translator ICs, or else I've made a mistake and I'm not measuring what I think I am. But since the current varies with pixel fill, I think my hookup is valid.
 

Altzone

New member
Thanks heaps for that, that is excellent confirmation and just what I expected based on the chip datasheet.
It is usually possible to power CMOS devices without a supply, via the inputs and the internal protection diodes, provided at least one of your inputs is HIGH of course.

Thanks
Dave.
 
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