Overclocking ADC

Question

Does anyone have experience overclocking an ADC by a small percentage?

I have an 80 MHz maximum sampling rate ADC. A new application requires a sampling rate of 82.8 MHz, exceeding the limit by 3.5% Not sure how much risk it is to exceed the margin by 3.5%.

Has anyone successfully overclocked ADC by a small percentage in projects?

Some converters have an inaccessible internal clock. For those, I'd say the answer is likely no, you can't. But if it depends *entirely* on external timing, then I'd think the engineering margin would be more than that. Just don't expect to get official support for it. — AaronD, Aug 19 '22 at 22:59
You may be able to do that reliably if you restrict other variables such as temperature range or voltage range but there will be zero guarantees. — Spehro Pefhany, Aug 19 '22 at 23:04
When you're unsure of the risk, then you're obliged to evaluate what overclocking might do. If it locks-up the ADC making it unresponsive, that's a no-brainer: don't do it. If a little more error is added to the sample output, or an occasional sample is corrupted, then that's a less-serious error. Time wasted in evaluating an ADC likely isn't worth the effort. I've overclocked an embedded SAR ADC by 25% in a non-critical app for my own use - but I have complete control of the operating environment....and stay well away from the edges of its operating envelope. — glen_geek, Aug 19 '22 at 23:13
Physics is typically not goverened by round numbers. They tested it to 80MHz and it works. Test the crap out of it at a higher frequency and pay attention to their guidance on clock requirements. — StainlessSteelRat, Aug 20 '22 at 06:09
If you want to run it at 82.8 MHz, test it to 85, or preferrably 90 MHz, at extremes of temperature and supply voltage. It it holds up reliably, then it should be OK at the lower frequency. If this is for a one-off hobby project, then you're done. If it's for a run of many boards, then you'll need to repeat this exercise every time the manufacturer changes the ADC batch. The new batch of ADCs may use a new process or design that still works at the advertised 80 MHz, but not at your extended frequency. — Neil_UK, Aug 20 '22 at 16:11
I'm guessing there should be some margins beyond the max 80MHz spec, just no guarantee on ADC behavior if pushing beyond the spec limit. Thank you all for the suggestions! — Jason L., Aug 21 '22 at 00:57
As in a certain percentage may not work or may fail in the field. — StainlessSteelRat, Aug 21 '22 at 23:36

score 4 · Answer 1 · answered Aug 20 '22 at 01:49

You can generally run MHz-class ADCs somewhat above their max clock. Occasionally vendors will even provide some performance plots extending 5 or 10% above the specified max clock. For example, the ADC12DL080 is an 80 MHz ADC, but TI provides this plot:

So overall performance is reasonable out to ~95 MHz, although THD and SNR do suffer when run higher than spec. I was curious and tested this, and did not get glitching until >105 MHz. I've seen similar results testing various other devices in that frequency range.

In your case I would study the datasheet carefully. If they spec performance at 82 MHz, and this is a one-off part where you can test it yourself, then I might be inclined to try it. I would not be confident ordering 1000 units though as you don't really know what the distribution of parts is going to be like.

Overclocking ADC

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