Hello,
Does anyone know a ballpark value for Atmel's ADC S&H switch on-resistance? It is not in the datasheet, it seems.
Atmel ADC S&H switch on-resistance
Nov 08, 2013
8 Replies
Yeh... what part?
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website:
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atmega8 Or any of their 8 bit microcontrollers.. (I think they're all mostly the same ADC-wise)
nevermind, I've found something..
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I recall something like 10k + 4pF from the datasheet... good to know someone made their own measurements and found similar results. Thanks,
Tim
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com
..on DuckDuckGo, I did not measure anything myself, just to be clear...
They do have a diagram in their data sheets that gives the resistor as
1..10k Ohm, which leaves some space for guessing...
Oops, wrong. it says 1..100k which is even more off
Atmega 8(L) datasheet Rev. 2486Q-10/06 page 202
That's probably just s***ty work on their part, but high ohm silicon paths are notoriously inconsistent; they are matched on chip (hence precise stable ratios, e.g., the R-R-R divider in the '555), but the absolute value has something like 3:1 uncertainty (10k might be 3 or 30k, say).
Tim
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com
For instance, the pull-up resistor is guaranteed 20-50k ohms, which is relatively tight as these things go IIRC. Depends on technique too (long trace vs. pinched trace).
Tim
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com
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