AD7091R-4 offset

Hello

Could you give me your advice about value of offset error of AD7091R-4 ?

Datasheet says +-1.5mV offset error at internal reference.

What is value of offset error at  5V external reference ?

As the result of test, offset error is about 1LSB at 2.5V external reference on evaluation board.

But offset error is about ~6LSB at 5V external reference on evalaution board.

(External power supply unit is used as reference).

Please let me know your advice

Regards,

Terumasa

  • 0
    •  Analog Employees 
    on Feb 3, 2015 12:10 AM

    Hi, Terumasa.

    Let me check on this. Meanwhile, can you provide the configuration of the relevant links on your test? What did you use for 2.5V external reference? Also what external power supply unit was it that you used? We don't usually recommend using power supplies as reference.

    Regards,

    Karen

  • Hi Karen,

    Thank you for your reply.

    Our customer will use ADR5045 (5V) as reference in his application.

    As the result of his test on his preproduction board, offset error is about 5~6LSB.

    Datasheet says that offset errpr is +-1.5mV using internal reference.

    For its verification if above reason of offset error is reference,

    he did below test using AD7091R-4 evaluatio board,

    Used Reference supply:  below 4 type

    REF193 (3V) on evaluation board,

    ADR5045 from preproduction board (5V)

    VDD on evaluation board(5V).

    Power supply unit   (2.5V or 3V or 5V.)  DC voltage/current generator_ADCMT 6156 

    http://www.adcmt-e.com/en/products/dc_voltage/6156/index.html

    Input 0V:: Connect Vin0 to AGND

    Test result

    Reference of ADR5045 or VDD on evaluation board or Power supply unit (5V)

       Offset error:  5~6LSB  (5~7LSB in the case of Power supply unit)

    REF193(3V) or Power supply unit (3V)

    offset error: 2~3LSB . (2~4LSB in the case of Power supply unit)

    Power supply unit (2.5V)

    offset error: ~1LSB

    In his preproduction board, offset error is ~1LSB when power supply unit (2.5V) is used as reference.

    His test accuracy may generate more offset error but  it seems that offset error is decreased by reducing reference voltage.

    So, my customer would like to know if offset error of AD7091R-4 is changed by reference voltage.

    Pleaes let me know your advice.

    Regards,

    Terumasa 

  • 0
    •  Analog Employees 
    on Feb 4, 2015 6:36 PM

    Hi, Terumasa.

    The figures on the data sheet specs were taken with the 2.5V internal reference. Using a different reference would show some differences in performance, I am still checking by how much. I'll get back to you as soon as check if we have data for an external 5V.

    Regards,

    Karen

  • Hi Karen,

    Please update this thread.

    Our customer must decide if he uses AD7091R-4 or another device and he needs this informatoin for decision.


    Please let me know your advice.

    Regards,

    Terumasa

  • Hello

    Could you update this thread about my quesiton ?

    Regards,

    Terumasa