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CFAL160128B Supply Voltages

raddybaby

New member
Hi,

I am am designing a PCB that will interface a CFAL160128B display to a PIC24...I want to run the pic and associated auxially circuits with +3.3V supply.

I'd like to confirm the supply voltages for the display:

From the CFAL160128B preliminary data sheet

VDD (Supply Voltage for Logic pin 27) min 2.2V typ 2.8V max 2.9V
IOVDD (???) min 2.2V , max 3.3V

Q1: Can I just use a LL4148 diode to drop my +3.3V supply to within spec (approx. 2.8V) for the OLED VDD?

Q2: Can i drive the display bus and control (db0,db1...wr, cs etc) lines directly from my PIC24 (at 3.3V)

Q3: What is IOVDD? (I think it the acceptable range of IO drive voltages refered to in Q2 but i'd like confirmation.)

If this is a problem/likely problem with my approach I can choose vdd=2.8V for my PIC24 and make voltage adjustments else where as needed...but I'd rather not do this.

Many thanks and cheers,
Neal
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I haven't used this display, but I'll take a stab at interpreting the data sheet.
VDD (Supply Voltage for Logic pin 27) min 2.2V typ 2.8V max 2.9V
IOVDD (???) min 2.2V , max 3.3V
IOVDD is the supply for the interface pins. But it looks like CFA's usage of the chip on this model has VDD and IOVDD bonded together on the same pin of the flex tail (pin 27). So you are limited by the lesser voltage, VDD, to 2.9 volts max for both logic and I/O.
Q1: Can I just use a LL4148 diode to drop my +3.3V supply to within spec (approx. 2.8V) for the OLED VDD?
Presumably.
Q2: Can i drive the display bus and control (db0,db1...wr, cs etc) lines directly from my PIC24 (at 3.3V)
No, not if you want to obey the spec sheet limit of VDD as the highest I/O voltage.
Q3: What is IOVDD? (I think it the acceptable range of IO drive voltages refered to in Q2 but i'd like confirmation.)
Mentioned above. You can see the definitions in the controller data sheet http://www.crystalfontz.com/controllers/LGDP4216.pdf, but because of the single pin for logic and I/O power, you are stuck, unless you want to go to the bother of level converter ICs. Using 2.8 volts for everything may be the easiest way out.
 

raddybaby

New member
Hi Cosmic,

Thanks for you thoughtful reply!

I am opting to use 2.8V for everything that i can (pic, mem, LCD etc) and I'll provide other supplies as required...I am going to end up with a LOT of diff voltages on my pcb but I guess that the way it has to be ;-)

Thanks again and cheers,
Neal
 
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