Mega4809 at DigiKey

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If 32KHz crystal isn't accurate (temperature) then calibrate given an accurate reference (GNSS 1PPS, clock from USB UART)

Well, that's pleasant.  However, what if you want to run accurately at 10.000MHz (such as for PWM or timers)...32.768 KHz isn't going to do much for you. 

How about simply including the standard full-swing xtal option?--it seemed to work fine for years & years. 

Maybe they'll forget how to make adc's & delete them too.  Maybe someone with the secret sauce left Atmel.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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rammon wrote:

... The Vpp for a 5V device is 0.6Vpp for one pin and 0.9Vpp for the other. I've never seen such a thing.

Sounds about right. The usual low swing oscillator, is actually a class A N-FET amplifier, current Fed. The N-fet gate threshold is well under 1V, and the p-p is usually about 2x the gate threshold.

The upper frequency should be defined by the current, and Xtal ESR. (ie change the current, and you change the upper MHz)

Lower C Xtals and lower ESR xtals, will oscillate up to a higher MHz as the non-oscillating loop gain increases with lower C.

The appeal of this circuit, is the Icc is quite stable, and does not vary with supply voltage - unlike a 74HCU04 approach.

 

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