AD7357 how to check the DC Accuracy in worst case condition

Hi

AD7357 is 14 bit , Due to DC accuracy concern , I need >0.3%

After calculated.....

DC accuracy = LSB[all of LSB , see the attachment as below ] / (2^14) , = 133 LBS / 16384  * 100% = 0.8%

AM I right ? or any part could meet this request ? ( Should meet automotive standard )

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  • Hi Kevin,

    The specifications on the datasheet were base from the results of the data gathered across temperature ( for AD7357 from -40C to 125C). What I mean is that for example at -40C, INL might be at its worst value but offset error might be fine, but at 125C gain error is fine and offset error is at its worst. So typically worst case linearity error, gain error and offset error will not take place on the same condition. Adding all the LSBs will not result of having the overall DC accuracy.

    Now to estimate the DC accuracy of the ADC ( for AD7357  LSB = 305.174uV) my idea would be ((Error*LSB size)/FullScaleRange)*100 = % accuracy of full-scale. For the positive full scale error ( which has the worst case) it is around 0.12% for INL it is 0.018%.

     

    The AD7357 has a AD7357WYRUZ model which is qualified for automotive application. Please check models on the last page (page 20) of the datasheet.

    Regards,

    Jonathan

Reply
  • Hi Kevin,

    The specifications on the datasheet were base from the results of the data gathered across temperature ( for AD7357 from -40C to 125C). What I mean is that for example at -40C, INL might be at its worst value but offset error might be fine, but at 125C gain error is fine and offset error is at its worst. So typically worst case linearity error, gain error and offset error will not take place on the same condition. Adding all the LSBs will not result of having the overall DC accuracy.

    Now to estimate the DC accuracy of the ADC ( for AD7357  LSB = 305.174uV) my idea would be ((Error*LSB size)/FullScaleRange)*100 = % accuracy of full-scale. For the positive full scale error ( which has the worst case) it is around 0.12% for INL it is 0.018%.

     

    The AD7357 has a AD7357WYRUZ model which is qualified for automotive application. Please check models on the last page (page 20) of the datasheet.

    Regards,

    Jonathan

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