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REF2025: Tracking error

Masayoshi Takahashi
Intellectual 1530 points
Part Number: REF2025
Other Parts Discussed in Thread: INA213

Hi team,

I got 2 questions about tracking error of REF2025.

1. I'd like to confirm the difference of the "Output voltage temperature coefficient" and "VREF and VBIAS tracking over temperature".

"Output voltage temperature coefficient mean" Both VREF and VBIAS will changed by temperature change.

So, What is the "VREF and VBIAS tracking over temperature" ?

2. Regarding tracking error equation (2), What is the temperature range?

Could you provide the calculation example?

Regards,

Yoshi

  • 0
    TI__Mastermind 19370 points

    Hi Yoshi-san,

    1. The REF2025 has dual outputs. Each dual output has it's own separate temperature drift known as "Output voltage temperature coefficient."

    A feature of the REF2025 is that regardless of how the output shape drifts, they will drift together and will always be close to each other in terms of accuracy. This is called "VREF and VBIAS tracking over temperature." The graph on the front page shows this effect and I have also drawn it below. The shape of the curves follow each other so they have similar drift shapes.

    2. The temperature range for "VREF and VBIAS tracking over temperature" is over the complete range. The equation for this is in section 9.3.1.

  • 0 in reply to Marcoo Z
    TI__Intellectual 1530 points

    Hi Marcoo,

    Thanks for your quick reply!

    Regarding question 2, If the customer uses under -40 to 125C. Temperature range is 165. Is this correct?

    Regards,

    Yoshi

  • 0 in reply to Masayoshi Takahashi
    TI__Mastermind 19370 points

    Hi Yoshi-san,

    That is correct 165C.

  • 0 in reply to Marcoo Z
    TI__Intellectual 1530 points

    Hi Marcoo,

    Thanks for your answer.

    I'd like to confirm additional question.

    When the customer calculate total accuracy of the device, the customer should calculate only equation 2. Is this correct?

    Or should the customer calculate as equation 2 + Output voltage temperature coefficient?

    Could you tell me which calculation is correct?

    Regards,

    Yoshi

  • 0 in reply to Masayoshi Takahashi
    TI__Mastermind 19370 points

    Hi Yoshi-san,

    Due to the separate outputs, I would consider the output of the device to be dependent on the the application. In general if one rail is being used for the ADC then the temp co error for the device is below for that rail. In which case the total error for the device in this application would be the accuracy + temp + long term drift + other errors. You can check out the app note in my signature for more details on that.

    Temp Co error = Vout * Temp Co * (Tmax - Tmin).

    The benefit of having 2 rails tracking each other is for applications that require a common mode voltage or use level shifting.

    If you use the front page figure from the datasheet, the VBIAS rail is being used on the INA213 while the VREF is used for the ADC. The VBIAS acts as the center point of the output of the OPA213 and any error on the VBIAS can act as an offset. When both the VREF and VBIAS rails track each other, you can eliminate the offset error from the temp co.