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The DNL and INL errors, the OpAmp offsets, the VDAC G error as well as
offsets all produce >> 1 LSB error. The test I ran in post #11 seems to work
just fine. I redid it as well at 12 bits, same results, albeit more accurate.
The problem is OP wrong Vref setting .....
I will do a setup this weekend in lieu of your not posting project to see if I get
the same result. You could also post at Infineon.com, but they wont go very
far on issue w/o project to examine.
Regards, Dana.
1717151792
If you are selected to first entry in configurator wizard (dbl click...
Maybe I am missing something but second entry seems to give full
analog range (to VDDA) from SAR datasheet :
SAR input range :
Note the DAC is limited to only 4.096V max output.
Regards, Dana.
SARs configed like this :
What sample rate you running SAR at ?
What specific pins did the auto assign for SAR inputs result in assignments ?
Not sure if this is affecting results :
Like when you flip the MSB of DAC and then start SAR while DAC still settling .......although I would...
Post the project archive so we can take a look. Use archive complete
when you do.
As an aside when you post code use the code tags menu item, it maintains the
indenting/format. Menu item is </>
The OpAmps are RRIO.
Note when you dbl click the component and set the config, you do not have to...
This might be useful, chart at end interesting :
https://blaauw.engin.umich.edu/wp-content/uploads/sites/342/2022/09/Ultra-Low-Power-32kHz-Crystal-Oscillators_-Fundamentals-and-Design-Techniques.pdf
Regards, Dana/
"Usually" that data is found in characterization data for the device. The fact
its not speced means it either is not reliable for spec sheet, eg. a part of
test procedure that could predict what performance would be or its simply
a parameter with bounds so great not worth repeating. Or given...
Your scope probes at 10X have a specified Cload.
You can decouple that with a series R from probe tip to xtal test point. Then the
effective Cprobeloading =
Of course your amplitude response is affected, but if all you care about is freq measurement....
The above transform equivalency often...
Sim shows (for 6.2K-dashed line and 1K solid line) :
Key is min cathode current to meet reference specs, of 1 mA. So your series R wants to
drop.
Regards, Dana.
This might help :
https://www.analog.com/media/en/training-seminars/tutorials/MT-037.pdf
https://pdfserv.maximintegrated.com/en/an/AN803.pdf
Regards, Dana.
Some FR4 discussions :
https://www.eevblog.com/forum/rf-microwave/9-10ghz-and-fr4/
https://electronics.stackexchange.com/questions/286472/when-to-use-a-special-high-frequency-pcb-material-and-not-fr-4-rogers
Regards, Dana.
When you progress at a later point in school here is an example of using'
state machine design to do a sophisticated intersection design. This shows
what modern tools look like, not rocket science, and a lot of fun. But
dont despair because it may seem foreign to your current state of learning...
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