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INA138: Current monitoring and circuit protection

Shai Berman
Mastermind 7405 points
Part Number: INA138

Hi team,

my customer wants to measure current with V(in+) 3.4 - 3.7 [V], the minimum current should flow in Rs is 20 [mA] and maximum current 1 [A], please advise the below:

1) V(out) from INA138 should be  0.3 - 2.7 [V]. What resistance should I use in shunt resistor and what resistance to RL? 

2) Same issue as section 1, the difference in V(in+) and Rs current. V(in+ )=3.4[V] and Rs  current should be between 5 [mA] and 450 [mA].

3) Can you offer me IC which can measure current for 4 different components, I know that INA418 can do the job, however, I need a smaller package.

4) Can you please suggest any recommended ESD protection with over current, over voltage and reverse voltage protection in one chip?

Thanks in advance and regards,

Shai

  • 0
    TI__Mastermind 32395 points

    Hello Shai,

    Thanks for looking into a TI solution.

    1. This all depends on the accuracy and power dissipation desired with shunt resistor. I would recommend looking into the data sheet section 8 which describes how to design this circuit. Equations 1 and 2 in data sheet also are important because they will decide the compliance voltage on the output. Given that you have a smaller voltage at IN+ (VIN+) this will limit the voltage you can achieve at output. As mentioned in data sheet you don’t want RL>500kOhm for accurate measurements. Overall I suggest programming all relevant equations and play around with some values to start and see what will give you best option for your application.
    2. Aside from what I mentioned above, the Vin+ voltage does not affect what the optimal Rs should be. The Vin+ does need to be above 2.7V for device to perform according to specifications.
    3. Unfortunately this is only quad channel current sense amplifier we have. You could look into quad channel devices in the difference amplifiers portfolio. I would recommend a quad operational amplifier, but more space would be required for gain setting resistors.
    4. For the most part our devices are not meant to withstand anything outside of the absolute maximum ratings. We do have this post discussing multiple options and schemes to deal with device protection: 



    Hope this helps and please post back if you have more questions or want more detailed explanations.

    Sincerely
    Peter Iliya
    Current Sensing Applications

  • 0 in reply to Peter Iliya
    Mastermind 7405 points
    Hi Peter,

    Thank you for your inputs and I'll keep you posted for further questions.

    Best regards,
    Shai
  • 0 in reply to Shai Berman
    TI__Mastermind 32395 points
    Of course Shai. I also saw that the link I included in my first post did not show up. Sorry about this. I just corrected it so you should be able to click it and get more information.

    Peter