• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 47 subscribers
  • Views 463 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Chaos while choosing the amplifier(current sense)

Lakshminarayana
Genius 3790 points
Other Parts Discussed in Thread: INA253, INA250, INA225

Hi,

I have an application where I need to measure the AC Current using CT and output the Analog voltage of 0-10 (to be specific Unidirectional).

I have chosen a CT which outputs 50mA(Is) for 100A(Ip) Ratio of 2000s:1p.

I have chosen a burden/Shunt resistor of 70.72Ohm as per the formulae Burden resistor = (Aref/2)/ (I secondary); Aref=10V, Isec = 70.70mA(50mA * 1.414);

So Voltage across the Burden resistor is +/- 5V.(Correct me if I'm wrong in calculation of burden resistor).

One way to get the Output Voltage of 10V by offset (ref) but I need to implement using amplifier.

(I have not designed any of circuit using Amplifier Yet and I would like to get to know more about them).

How INA 225 can be used in this application?

I also came across the INA253 which is new TI Current sense product which has built in shunt resistor of 2mOhm and supply is limited to 5.5V I believe this can not be used in my application since output V > Supply V. Are there any other Current sense Amplifier with built in Shunt with wide range of Supply Voltage(in my application 10-15V) and ref design. 

Could you please help me with choosing amplifier?

Thanks. (Expecting an early response since have time bound issue in completing this project)

Lakshminarayana K N.

CT.pptx

  • 0
    TI__Mastermind 32670 points

    Hello Lakshminarayana,

    Thanks for using the forum to get your question answered.  Would the INA250 work for you if you wanted an integrated shunt.  The INA225 would also work but no integrated shunt.  

  • 0 in reply to Javier Contreras4
    Genius 3790 points

    Thanks for your inputs.

    What would you think the best option to go in my application an Integrated or external shunt for CT?

    Also please attach the reference design or example design for CT using opamp.

    Thanks.

  • 0 in reply to Lakshminarayana
    TI__Mastermind 32670 points

    Hello Lakshminarayana,

    I don't think I have a reference design with at CT but I will take a deeper look and ask a few colleagues.  

    For the CSA (Current Sense Amplifier)  suggestions please give me some key specifications you are looking for.  I know you need an output from 0V to 10V.  For example what is the offset you require?  Are you ok with the input bias current that our CSAs have? How are you biasing the CT: Will the common mode be moving?  Are you concerned with drift?  So there are many questions that need to be taken into account.  Please see our training videos to help with some of the specification you may need to look at for your design.  There will be tradeoffs and I want to make sure you know what they could be.