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TL431: VREF Deviation at different Temp/TA

Brian Wang0928
Genius 12700 points
Part Number: TL431
Other Parts Discussed in Thread: REF3025, TLA431

Tool/software:

Customer would like to know the deviation of the VREF at different temperature. Is that related to below equation?

How do i calculate VREF deviation at diff. temp?

Regards

Brian

  • 0
    TI__Expert 5310 points

    Hi Brian,

    What is the temperature range of interest for the customer?

    Thanks,

    Jackson

  • 0 in reply to Jackson Wightman
    TI__Genius 12700 points

    Could you offer such curve? Since customer is doing the FuSa power with TUV, they need more exact data and how to calculate it. pls be understanding. thanks.  

  • 0 in reply to Brian Wang0928
    TI__Expert 5310 points

    Hi Brian,

    I asked about the temperature range to help with device grade selection which would also improve the temperature drift. The figure you are looking for can be found in the TL431 datasheet Figure 6-1. Please keep in mind this is a typical curve meant to serve as a guide. Max and minimum values for temperature drift and reference voltages can be found in the electrical characteristics table.

    Thanks,

    Jackson

  • 0 in reply to Jackson Wightman
    TI__Genius 12700 points

    Thanks Jackson.

    Looks Fig 6-1 is for the I and Q type. My customer is using B type (TL431BI). Is that possible you can offer the similar curve with B type?

     

    Regards

    Brian

  • 0 in reply to Brian Wang0928
    TI__Expert 5310 points

    Hi Brian,

    TL431BI is the industrial temperature grade, also known as the "I type" that you have mentioned, which has a temperature range of -40°C to 85°C.

    The B accuracy grade has improved reference voltage accuracy.

    However, the temperature drift specification is the same as the other versions of the same "I" temperature grade. This can be seen on page 7, 10, and 13 when comparing the three reference voltage accuracy grades and seeing the deviation of reference input voltage over full temperature range stay the same for all versions of the "I" temperature range:

    Additionally, figure 6-1 is to be used as a guide. For maximum temperature drift values, please refer to the respective electrical characteristics tables. So in summary, the "B grade" also applies for figure 6-1.

    Thanks,

    Jackson

  • 0 in reply to Jackson Wightman
    TI__Genius 12700 points

    Got Thanks.

    One more question. is that possible to know how to calculate or get initial accuracy of B(0.5%)，A(1%)，Blank(2%)

    Regards

    Brian

  • 0 in reply to Brian Wang0928
    TI__Genius 12700 points

    If we used the "Equal proportion calculation" based on Fig 6-1 at 100degre, the VREF min and max value will be likely as below for TL431B (0.5%). Could you check if it's making sense or not? 

  • 0 in reply to Brian Wang0928
    TI__Expert 5310 points

    Hi Brian,

    Please use the values provided in the electrical characteristics table for the corresponding part of interest to find the maximum temperature drift and initial accuracy numbers. For example, the highlighted sections of TL431BI below:

    Do not use figure 6-1 for maximum and minimum calculations, this figure is only meant to be used as a general guide. Pages 6 through 14 contain the numbers for maximum and minimum temperature drift calculations.

    Thanks,

    Jackson

  • 0 in reply to Jackson Wightman
    TI__Genius 12700 points

    Thanks. 

    Customer would like to get the VREF,min and VREF,max at TA = 100degree. In the E/C table, it is only TA=25degree.

    How to estimate VREF at TA=100degree for TL431B(0.5%)with temperature Coefficient ? 

    Regards

    Brain

  • 0 in reply to Brian Wang0928
    TI__Expert 5310 points

    Hi Brian,

    Please view the "Deviation of reference input voltage over full temperature range" on page 14 of the TL431 datasheet for the TL431BQ (0.5% accuracy, -40°C to 125°C temperature range):

    It is listed as 34mV max. What accuracy is the customer trying to obtain?

    Thanks,

    Jackson

  • 0 in reply to Jackson Wightman
    TI__Genius 12700 points

    On the page 14, the condition of Vi(Dev) is at Amb temp: 25degree, not at full range temp, isn't?

    Customer just specify to know the VREF,min and VREF,max at full temp range. Could you offer these values ! Very thanks. 

    Regards

    Brian

  • +1 in reply to Brian Wang0928
    TI__Expert 5310 points

    Hi Brian,

    The table on page 14 says the following: "over recommended operating conditions, TA = 25°C (unless otherwise noted)". On the "Deviation of reference input voltage over full temperature range" specification, there is a note (1). Under the table, this note reads "The deviation parameters VI(dev) and II(dev) are defined as the differences between the maximum and minimum values obtained over the rated temperature range." Since this is for the TL431BQ device, the temperature range is -40°C to 125°C. So, the deviation of reference input voltage of full temperature range is for the whole -40°C to 125°C temperature range.

    In terms of the absolute maximum and minimum VREF values, it is best practice to consider the worst case over temperature, which will be [2.483V - .034V, 2.507V + .034V], as this is what we guarantee in the datasheet. 

    However, for example, if you singled out an individual TL431 device, and measured the VREF to be 2.502V, the output voltage would never shift more than 34 mV total. Some, but not all, possibilities are:

    VREF could vary from 2.468V to 2.502V (34 mV total deviation)

    VREF could vary from 2.485V to 2.519V (34 mV total deviation)

    VREF could vary from 2.502V to 2.536V (34 mV total deviation)

    For this reason, it is best to consider the worst case of 2.449V on the low side and 2.541V on the high side.

    If the customer would like a device with improved temperature drift, they could consider TLA431 (PTLA431QADBZR) or REF3025 (REF3025AIDBZR). Please let me know if there are any further questions.

    Thanks,

    Jackson