Calculating max Freq at lower V

I'm going to use a PIC (18LF4620) at 3.3V for the first time, what is the max frequancy I can run it at? I had a look at the equation MC give in the datasheet, but it seems I am missing something as I don't get the same answer they do.

Thanks,

This reply was posted by: eng1

Quote:
Originally Posted by Boomslang
I have a question that might be relavent to this thread.

I'm going to use a PIC (18LF4620) at 3.3V for the first time, what is the max frequancy I can run it at? I had a look at the equation MC give in the datasheet, but it seems I am missing something as I don't get the same answer they do.

Thanks,

I calculted a maximum frequency of about 25 MHz @ 3.3 V. That should be correct according to Figure 26-3 in the datasheet. What did you get from your calculations?

I calculated it to about 11Mhz, but I am sure I'm not using the equation right. 25Mhx looks more like it. Would you be so kind to post the equation with some real world values in, and how you got to the answer.

Thanks,

Boomslang said:

I calculated it to about 11Mhz, but I am sure I'm not using the equation right. 25Mhx looks more like it. Would you be so kind to post the equation with some real world values in, and how you got to the answer.

Thanks,

Click to expand...

Sure, I used the following equation:
f = 16.36 * (V - 2) + 4

f = 16.36 * (3.3-2) + 4 = 25.268 MHz

hahaha... I made a stupid error. I read (16.35Mhz/V) as 16.35 devided by V instead of 16.35Mhz per volt... I had it as 16.35 devided by 3.3V

So I should be pretty safe running at 20MHz...