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UCD3138: UCD3139 Error Value EADC

maria
Prodigy 55 points
Part Number: UCD3138

Hello,

I am having real trouble reading the value of the eadc output in open loop mode

i m injecting a 3V input in the EAP0 and injecting the other pin (EAN0 ) to the ground and using the lab4 code , i m trying to get the value of the input voltage in the eadc output but the results are not understandable to me ( how can i read the Error value correctly?) or is it the Abs value that i should read to get the correct results .

i m using the ucd control card with the UCD3138PSFB evm board.

Thank you

  • 0
    TI__Genius 17090 points

    I would suggest using just the control card by itself, so you aren't interfering with the circuits on the PSFB EVM.  Note that the EVM only has a range of 0 to 2.5 volts, so if you put 3 volts in you will be maxing it out.  It should not damage it, but you will always see a maximum value,  You can read either the EADC Value or the Absolute value.  Note that the EADC only has a limited range, so you need to adjust the DAC so that the difference between the DAC and the input value is less than the range of the EADC.  The dynamic range of the EADC varies depending on the EADC gain.  If you set the gain to 8, the range is only +- 32 mV.  If you set the gain to 1, the range is still only +-256.  mV. 

  • 0 in reply to Ian Bower
    TI__Genius 17090 points

    It's actually 1.6 volts, not 2.5  2.5 is for the ADC, not the EADC.