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INA201 Input surge protection and gain error

Michael Markowitz1
Prodigy 50 points
Other Parts Discussed in Thread: INA201

Hi,

I'm building a high side switch for overcurrent shutdown device using INA201 like in Figure 29 page 15

I need to withstand milstd1275  spec which means that I need to withstand surge voltages of 100V. Can adding input protection resistors of about 5-10K provide me this protection assuming the the precise gain is not important in our application.

According the the datasheet 7.4.1 (page 17) I can put input resistors for filtering (figure 27) and calculate the gain error.

In 7.4.3 it says that i can rely on the internal ESD diodes as long as I take into account the gain error.

in 6.2 footnote 2 (page 3) it says that i can exceed the voltage rating as long as the current is lower than 5mA.

Question 1) is it correct that if I put large resistors (about 5-10K) that will limit the current to less than 5mA I will get input protection against large voltage (100V) surges using the internal ESD diodes?

Question 2) Is there a formula that I can calculate the new gain including the input resistors i added?

thank you,

Michael

  • 0
    TI__Mastermind 18790 points
    Hi Michael,



    A1) Yes, it is true that if you can limit the current at the pin to 5mA, then you can exceed the abs max characteristics present, but not by the margin you are hoping to achieve. Typically the current limitation will only buy you an extra few hundred millivolts at best.

    A2) Yes. That formula is found under 7.4.1 of the datasheet.

    Unfortunately I don't think this approach is going to be successful for you. If you examine the formula referenced above in 7.4.1, you'll see that the error you would introduce to the circuit from 10k resistors on the input lines is between 66.7% (only taking into account the filter resistors) and 75%(including the +/- 30% tolerance of the internal parts), which is a worthless metric at that point in my opinion.

    I would recommend checking out our TI design found here:

    www.ti.com/.../tidu473.pdf

    While it is not a plug and play solution for your problem, it will provide you some insight into external protections that you could possibly modify to the INA201 to be protected from the surges in question. Let me know if you need anything else. Hope this helps.

    Carolus