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TMS320F28377S: lower cost ADC reference circuit design

Part Number: TMS320F28377S
Other Parts Discussed in Thread: REF3030, OPA2320

C2000 Team,

This post has some useful information on the reference circuit for TMS320F2837x devices:

https://e2e.ti.com/support/microcontrollers/c2000/f/171/p/477506/1721275#1721275

The minimum recommended configuration here is a single reference, e.g. REF3030, and one buffer amp per two ADCs, e.g. a single OPA2320.  The cost of this add up, especially in 12-bit mode where you should not need quite as good a reference as in 16-bit mode.

QUESTION: Have we ever looked at the performance with a low-cost shunt regulator for the reference, such as the LM4040C30, with or without buffering?  This would be for 12-bit mode.

Regards,

David

  • Hi David,

    With a buffer you can certainly use this or any other reference.

    Any inaccuracy in the reference will affect the overall gain error. For this IC 0.5% accuracy will correspond to 4096 * 0.005 = 20 LSBs of gain error. It's usually very pessimistic to just add this on top of the ADC gain error to determine the system gain error, so we recommend that you add them in RMS to estimate the system gain error. So for F2837xS, the total gain error would be around sqrt(20^2 + 5^2) = 21 LSBs.

    You also probably want to consider the noise, although this is a little more fuzzy if you are using a buffer since you can add some filtering at the reference output before the buffer input to get the noise smaller as needed. The LM4040C30 seems like it should be plenty low noise for driving a 12-bit ADC reference.

    As far as using this to directly drive the ADC reference pin, I'm not sure what the performance would be. You can see from the linked e2e post that we saw clear performance issues when doing this using the REF series voltage references.