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TMS320F280025: ADC only have 11 bits ADC resolution

Strong ZHANG
Expert 4490 points
Part Number: TMS320F280025
Other Parts Discussed in Thread: C2000WARE

Hi Team,

My customer are using 48 pin F280025C for design using 3.3V for VREFHI and VDDA, the example code they use is adc_ex1_soc_software.c from c2000ware,  the issue is that they found ADC result only have 11bit, for example, read 3.3V on any pin the value is about 2048, and 1.65V is about 1024.

C:\ti\c2000\C2000Ware_3_02_00_00\driverlib\f28002x\examples\adc

They did not found this issue at F280025 controlcard with the same code，only have this issue on their board.

When they change the ADC_INTERNAL to ADC_EXTERNAL for the below function, then everything is ok and the resolution is 12bit.

SetVREF(ADC_ADCA, ADC_EXTERNAL, ADC_VREF3P3);

what is the problem when use ADC_INTERNAL configuration  and any suggestion for this?

  • 0
    TI__Guru 60865 points

    Hi Strong,

    Are they forcing a voltage on VREFHI?  If yes, internal reference mode can't be used because internal reference will attempt to force a reference voltage OUT of the device onto the VREFHI pin, so if another source is driving the pin there will be contention.