[SOLVED] 3.3 volts on PIC microcontroller.

[mr_anderson]

Hi
I have a 5 volt 2 Mhz signal that is being generated by PIC18F87J60 and PIC16F877A, I am trying to feed that signal to a take an input of 3.3 volts. The problem is the 5 to 3.3 volt converter will take 7 days to arrive so I am trying to come up with a quick solution.

I went through the data sheet of 87J60 and found that it has some 3.3 volts feature but didn't really understand is that for ethernet only or I can have 3.3 on all the pins?

I also tried to connect 4 diodes in series with one 4.7K resistor to get a voltage drop from 5 to less than 3 volts but that is giving some noisy results, any suggestions will be highly appreciated.

Thx.

 

[barry]

How about a voltage divider? Also, 4 diodes will give you about 2.8V of drop; add to that the IR drop of your resistor might take your voltage out of range. Just because your device is running off of 5 Volts doesn't mean your OUTPUT is 5V. Have you looked at your signals with a scope?

 

[kam1787]

try a resistor voltage divider

what type of diodes did you use?

 

[Kripton2035]

I dont understand : your PIC18F87J60 supports max 3.6V : how can it generate a 5V signal ?
replace the 16f477 with a xxLFxxx pic so it supports 3V and power all your project with 3V
would be the most effective way to do this
but in a hurry, I think like the others a simple voltage divider with 2 resistors would do the trick.

 

[paulfjujo]

:!:
use a simple resistor divider

for output 
5V level ------ 1.5 K -----|-------> 3,3 LEVEL
                                   |
                                 2,2K
                                   |
----------------------------|----------Gnd

and direct link in other way 3,3V out --> direct to 5V TTL input

sorry, i don't know how to manage spaces , even with CODE balises or ???
2,2K is between 3,3V output and ground..

 

[mr_anderson]

Thank you guys very much.
U are right about the 87J60 it uses 3.3 but apparently the board that I am using had a 3.3 to 5 converter. This is why I was seeing the 5 voltage. Thank you again for pointing that out.