2
\$\begingroup\$

I want to run an AVR off the internal 8Mhz RC oscillator without any prescaller and want to make sure I have enough voltage for proper operation.

\$\endgroup\$

1 Answer 1

Reset to default
10
\$\begingroup\$

2.4 volts.

Calculated from this graph (which could have more thoughtfully placed guide lines!)...

enter image description here

Since the voltage is linear with clock speed between 1.8V and 2.7V (as per datasheet), it is a simple linear interpolation to get the answer...

enter image description here

\$\endgroup\$
2
  • \$\begingroup\$ +1. Just a comment aside; this graph curiously shows a different result than one would expect considering that in theory the lower the voltage of a core, the lower the voltage sweep for the same slew rate and consequently the higher the frequency, anyway, whatever... \$\endgroup\$ Commented Oct 28, 2017 at 7:59
  • 2
    \$\begingroup\$ @andre_teprom I assumed that the higher voltage at supper faster speeds is needed because the the RC time constants of the gates and lines. Higher voltage -> more current-> faster charge/discharge. Does not explain the inflection point at 2.7V though. Maybe should be its own SE question! :) \$\endgroup\$ Commented Oct 28, 2017 at 16:53

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.