We are experiencing inconsistent measurement accuracy between devices when using the C5535 SAR ADC’s internal bandgap reference. With identical hardware and firmware, I can only conclude that there is unacceptable variation in the 1V bandgap references.
This post (https://e2e.ti.com/support/dsp/c5000/f/109/t/469211 ) confirms that they are tested, but not the specified accuracy.
In this old post from 2013, (http://e2e.ti.com/support/dsp/c5000/f/109/p/265742/935679?pi239031349=1&pi317310=1 ) a TI employee stated this regarding the C5505’s reference:
“I had a discussion with the designer and looks like the internal reference voltage will not be very accurate and has more tolerance limit, due to this the count value could deviate. That’s the reason that you are seeing the deviation in the count value. Is it possible in your setup to have external reference source…”
Does this advice to avoid the internal references on the C5505 also apply to the C5535? There is nothing in their datasheets or errata that explain/elaborate on the above.
To re-ask the final unanswered question in the above post, what is the expected accuracy of the bandgap references?
Thanks,
Stan
