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Current Sense High Frequency

Ricardo Pedro60
Prodigy 70 points
Other Parts Discussed in Thread: THS4601, THS4131, TIDA-00976, THS3217, OPA690, OPA659, LMH6609, TINA-TI

Hi all,

I am designing a system to sense the current in a loop. The current signal is sinusoidal and has 15MHz frequency.

Because the ground noise, I want sense in high side. TI has any part with this bandwidth? I searched but no results..

Thanks

  • 0
    Guru 140200 points

    Hi Ricardo,

    what do you mean by "loop"? Can give more details about your application?

    Kai

  • 0 in reply to kai klaas69
    Prodigy 70 points
    Hi,

    Thank you.

    I have a signal, that is: +12V->Resistor->LC oscillator->GND. The resistor was introduced by me to measure the current. The sinusoidal has 2Vpp.

    thank you.
  • 0 in reply to Ricardo Pedro60
    Guru 140200 points
    Hi Ricardo,

    do you mean, you have 2Vpp across the shunt? (By "shunt" I mean the resistor you introduce to measure the current.)

    Kai
  • 0 in reply to kai klaas69
    TI__Mastermind 32375 points
    Hello Ricardo,

    There are no current sensing amplifiers with bandwidth to support 15 MHz. You might want to look through for high-common mode voltage transimpedance amplifiers, such as the THS4601 that can support your high-side configuration with 12V bus rail. I will move this thread to the high-speed amplifiers forum.

    Sincerely,
    Peter Iliya
  • 0 in reply to Peter Iliya
    TI__Genius 15975 points
    Hi Peter,

    You may want to take a look at the below TI Design for high side current sensing using the THS4131, which should support a bandwidth of 15MHz.

    www.ti.com/.../TIDA-00976

    Please let me know if you have additional questions.

    Best Regards,
    Rohit
  • 0 in reply to Rohit Bhat
    Prodigy 70 points

    Thank all for answers.

    The information 2Vpp is "incomplete"/wrong: the correct is: the current oscillate between 10mA and 20mA.

    I will look to TIDA-00976, thanks. And after, I will post my questions :)

    Thanks

  • 0 in reply to Ricardo Pedro60
    Prodigy 70 points

    Hi, 

    I read the TIDA-00976 and looks nice for my situation. However, I will need a single ended output, no differential like in TIDA-00976. What amplifier your recommend for this signal conditioning? I see the THS3217 for example, but there is other cheaper?

    Thanks

  • 0 in reply to Ricardo Pedro60
    TI__Genius 15975 points
    Hi Ricardo,

    I think the amplifier options for your signal conditioning would be LMH6609, OPA690 or the OPA659 (FET input). What value current sense resistor are you planning to use for your high side current sense application?

    I think you should be able to configure the op-amp in difference amplifier configuration for sensing the high side current. Please let me know if you would need help with building the circuit. Also, what is the desired op-amp output swing you are looking for sensing the 10mA-20mA current?

    Best Regards,
    Rohit
  • 0 in reply to Rohit Bhat
    Prodigy 70 points

    Hi Rohit,

    Thank you for your answer.

    When you talk about LMH6609, OPA690 or OPA659 is in substitution the THS4131?

    So, I have a 10mA-20mA signal. I have two solutions?
    1) use a fully differential amplifier (like THS4131 in TIDA-00976) and after an amplifier to subtracte Vout+ - Vout-
    2) use directly an amplifier (like OPA659) for substracte +12V - Vrsense

    Right? So, I need an amplifier with Supply greater than 12V. Rsense I can select, is not fixed yet.

    After the signal is "conditioned" I will put the signal in a comparator to obtain a square wave to adquire the frequency in a microcontroller.

    Thank you!

  • 0 in reply to Ricardo Pedro60
    TI__Genius 15975 points
    Hi Ricardo,

    Yes, the amplifiers I recommended are in substitution to the THS4131.

    Yes, you can approach your problem using two solution as you have suggested either using a fully differential amplifier (like the THS4131) or using an op-amp in difference amplifier configuration that will provide single-ended output for 12V - Vrense operation.

    I think it should be ok to select an amplifier with supply less than 12V, because the op-amp inputs will isolated from the 12V using some series resistor. I would recommend you to simulate your circuit in TINA-TI before practically implementing the circuit on a pcb.

    Best Regards,
    Rohit
  • 0 in reply to Rohit Bhat
    Prodigy 70 points

    Hi,

    Thank you for your answer.

    I will simulate and after post here the results.

    Thanks,