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DAC8775EVM: DAC8775 read drift during high temp

Alex Chen9
Expert 1075 points
Part Number: DAC8775EVM
Other Parts Discussed in Thread: REF5050, DAC8775

HI Sir

I want to design a 4 set 4-20mA,

test the ADI/AD5755-1, TI/DAC8775+External ref(Ref5050)

After 60 degree temperature test, I found the TI accuracy is bad than ADI, please advise it,thanks

  TI (DAC8775+REF5050):FSR 0.06-0.07%  ADI(VREF Intergrated) :FSR 0.02%

 

    

  • 0
    TI__Mastermind 46290 points

    Alex,

    The figures that are shown in the datasheet,at least on the TI side, are collected over several units from different lots. Furthermore, they are guard-banded by a study on the instrumentation repeat-ability at final test and other long-term yield concerns. The reason things are done this way is to ensure that the datasheet can serve as, basically, a guaranteed number across >99.9% of units.

    It would appear that you have measured IOUT accuracy on two EVMs. In this case, the ADI part was better. Over multiple units, you will likely see a distribution of instances when TI is better and when ADI is better.

    That said, the datasheet does acknowledge a limitation for the 4-20mA output accuracy on DAC8775 versus the other ranges - so some of this is expected. From studying the data internally there is a larger guard-band on the 4-20mA range than the others, so there is a chance that in the near-term we will tighten that specification. Whether it will match the other ranges or just be close is to be determined.

    In the end, I would suggest that you / your customer make decisions based on the datasheets - not information collected on their own bench using EVMs. It is not to discredit their measurement capabilities etc., but we have already gone through the effort of very exhaustive measurements so there typically isn't much merit for reproducing the same effort.