AVR 12Mhz with VCC 3V?

General discussions about V-USB, our firmware-only implementation of a low speed USB device on Atmel's AVR microcontrollers
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Tommi

AVR 12Mhz with VCC 3V?

Post by Tommi » Sat Sep 29, 2007 5:49 pm

Just wondering. The basic design shows the tiny2313 (or other AVRs) with 12Mhz clock at VCC 3.3V. But (all known) datasheets only permits clock frequencies >10Mhz only to VCC from 4.5 to 5.5V.
When i use the lower rate at 3v, is this an supported "overclocking" of the MCU?

Tommi

christian
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Objective Development
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Post by christian » Mon Oct 01, 2007 1:20 pm

If you stick with the words of the data sheet, yes, then this is overclocking.

There are AVRs with a more precise specification of supply voltage vs. allowed clock (in a diagram). Since the rating is consistent with the values given in other AVR data sheets, we assume that the other AVRs have a similar characteristics. See, for instance, the ATMega88 data sheet on page 302, section "Maximum Speed vs. VCC".

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