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Question of the INA301 Delay Time

Wayne Chen (ex FAE)
Guru 15950 points
Other Parts Discussed in Thread: INA301

Hello Sirs,

Would you pls advise how to make faster response time on the INA301 EVM? We got ~50us delay time with 2A current limit, 12V Vcm and _5V Vs, while we found 1us (mx) specification on its datasheet?







Thank you and Best regards,

Wayne Chen
12/20/2016

  • 0
    TI__Mastermind 18780 points

    Dear Wayne,

    Could you post the calculations you used to set up Vlimit from the 2A current limit please? Please include your resistor value at R3.

    Thanks,

    Carolus

  • 0 in reply to Carolus Andrews
    Guru 15950 points

    Thank you for your concern, Carolus

    We used INA301A3 option (100V/V) with 1mOhm Rshunt -> I(limit) = 2A -> Vlimit = 2mV * 100 = 200mV -> R(limit) = 200mV / 80uA = 2.5kOhm

    Thank you and Best regards,

    Wayne Chen
    10/21/2016 

  • 0 in reply to Wayne Chen (ex FAE)
    TI__Mastermind 18780 points
    Hey Wayne,

    Sorry to keep you waiting. Could you also send me your testing setup? All of your calculations look great. I am going to recreate the test on this end and see what results we come up with.

    Carolus
  • 0 in reply to Carolus Andrews
    Guru 15950 points

    Hello Carolus, Thank you for your reply. We testd the INA301 with a hand held printer as the below bloack diagram...Wayne Chen

  • 0 in reply to Wayne Chen (ex FAE)
    TI__Mastermind 18780 points

    Dear Wayne,

    I was able to recreate your setup and have a look. Are you desigining in the worst cases for offset voltage and input overdrive? During my runthrough of your setup, I was able to recreate your problem when I attempted to bring my output directly to the point of the limit voltage. However, all parts come with a small Vos which will be amplified by the gain and be present on the output as well. You need to take this voltage into account with your limit voltage. Once I did this in the lab, the part's response time shifted into datasheet parameters.

    To visualize this, I would recommend applying a function generator to the inputs and sweeping through Vpp of a square wave to see what I am talking about. At the point of the trigger (Vlimit = Vout), you will see the limit pin pulled low, with the effects you're concerned about. Continue sweeping through a few more millivolts (15-20) and you should see what I am referring to on your scope. Let me know if this makes sense and if you need anything else.

    Carolus

  • 0 in reply to Carolus Andrews
    Guru 15950 points

    Hello Carolus,

    Thank you for your elaborate. Delay time within a few micro seconds can still meet our customer's requirement. Will product line update the delay time specification or add application note in the INA301 datasheet to address the Vos impact?

    Thank you and Best regards,

    Wayne Chen
    10/25/2016