• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 46 subscribers
  • Views 318 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

About ADS1146 ,How can I know maximum value of electrical specifications?

Shinichi Inoue
Guru 21566 points
Other Parts Discussed in Thread: ADS1146, ADS1147, ADS1246

Dear specialists

I am writing to ask you about ADS1146's electrical specifications.

They don't have maximum value ,only describe typical value.

How can I estimate the maximum value?

 I want to know especially offset error、offset drift、gain drift.

Do you have any guideline or empirical data?

Background of this question, my customer must check up conversion error at the worst case .

Best regards.

Shinichi Inoue

  • 0
    TI__Guru 55466 points

    Hello Shinichi,

    The ADS1146 datasheet electrical table on page 3 provides the maximum offset and Gain error specs.  The datasheet guarantees a maximum offset of +/-1LSB and a maximum gain error of +/-0.5%.  These Minimum and Maximum specifications apply from -40C to +105C.  The datasheet only provides the typical offset drift specifications; 100nV/C for PGA=1; and Gain error drift of -3.5 ppm/C at Gain=128; however we guarantee that the device will always have smaller errors than the guaranteed maximum specifications above.  The device provides a Self-offset calibration routine that could be used to help mitigate the errors due to offset drift.  The ADS1147 device offers the system ambient temperature monitor that could be used to trigger offset calibrations when a large temperature change has occured.

    The ADS1246 (24 bit version) is a higher precision device that provides smaller offset and Gain error specifications.

    Best Regards,

    Luis

     

  • 0 in reply to Luis Chioye
    Guru 21566 points

    Dear Luis

    Thank you for your reply.And then I sent to the customer,He was confirming the answer.

    Customer knows Self-offset calibration function,but he has to use without Self-offset calibration.

    The reason is following .Once the product is turned on, will continue to operate for a long time without turned off.It's no time to calibrate.

    So he has to do without calibration.He is going to calibrate with extra circuit .

     Please support three more questions. 

    1. How much is offset error without calibration? Datasheet says after calibration spec.

    The customer just want to know the spec without calibration,No guarantee.

    He is going to calibrate extra circuit,and he has to know range of the error.

    2.About the offset error.

    Is offset error  always the same value  when the power is turned on?

    I think it will be a same value.

    3.About the gain error

    Is the gain error always the same value when the power is turned on?

    I think it will be a same value.

    Best regards,

    Shinichi Inoue

  • 0 in reply to Shinichi Inoue
    TI__Guru 55466 points

    Hello Shinichi,

    The datasheet of the ADS1146 guarantees only the offset after calibration to +/-1 LSB.  In most applications, the user will simply issue the SELFOCAL calibration command during hardware initialization after powering up.  In applications where the user needs to perform a system offset calibration including the offset of an external circuit, (such as an amplifier or buffer), the user will typically issue a SYSOCAL command to correct for both internal and external offset errors while forcing 0V differential to the inputs of the circuit (including the buffer or external circuit).

    Since the ADS1146 the device has a chopper-stabilized PGA the offset is very stable over time.  The uncalibrated offset may be in the order of ~100uV approximately (not guaranteed).  We do not have immediately available uncalibrated offset histograms, since we guarantee the offset after calibration.  The offset error at power up should be the same provided the same conditions are present.

    The gain error is the same when the power is turned on, provided the same conditions are present.  The initial gain error is guranteed to be less than 0.5% and the gain error drift is in the order of -3.5ppm/C for gain=128V/V and 1ppm/C for Gain=1V/V.

    Thank you and best Regards,

    Luis