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CFAG320240CX-TFH-TTS with 3.3V host


New member
Just getting started here with the CFAG320240CX-TFH-TTS's and thought I'd verify couple things about the best way to use with a 3.3V host before putting the hardware together.

Reading the datasheet v1.1 on page 2 in the table "COMPARISON OF CFAG320240CX SERIES WITH CFAG320240C0 SERIES" it is saying "Power requirements (logic and operation) - 3.3v - 3.6v or
4.6v - 5.5v". I think this could be interpreted that the whole module could be operated with 3.3V instead of 5V. Doing this without any modifications the problems I could see are the 3.3V regulator on board in series with the S1D13700 core vdd being powered from 3.3V input voltage. Also I don't know if the VEE DC/DC converter is meant to be happy with 3.3V input.
I didn't see any other mention about 3.3V operation in the datasheet. Might be a good idea to clarify this a bit.

I suppose one option could be to just leave everything as it is and power the display from 5V and use a 3.3V host. It could work just fine. I can also see there are series resistors in the host interface so with most 3.3V devices having protection diodes it should be ok. But having a closer look into the S1D13700 datasheet makes me think this would be out of spec. /RD, /WR, /CS and /RESET are schmitt trigger inputs with 2.0V HIGH level minimum threshold so they should be fine with 3.3V input. But the databus and A0 have a 3.5V minimum HIGH level according to the S1D13700 datasheet.

I see next to the 3.3V regulator on the PCB there is a jumper called JV that seems to allow changing the S1D13700 host io voltage to 3.3V from the regulator output. I suppose it should be ok to use this option and it's probably designed to be used for this but as I didn't see any mention about this, any side effects that I should be aware of ?
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CF Support

According to our factory engineer, remove U9 and move JV to the other side of the jumper to make the part work in a 3.3v system.


New member
i've tried to remove U9 and move JV jumper, but it doesn't work.
VO and VEE pin are both 0V, and on the screen i can't see anything.

The PCB is signed as 320240CX rev.D