• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 49 subscribers
  • Views 231 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

INA280: problems with the current sense amplifier INA280A4IDCKR

Martin Holguin
Intellectual 270 points
Part Number: INA280
Other Parts Discussed in Thread: INA240

Hello everyone,


I am trying to measure the current of a peltier cell that I am controlling with an h-bridge and a PWM signal.
I control the duty cycle of the PWM to control the voltage in the peltier cell, but I want to sense the current of the peltier so I plan to use an INA280A4IDCKR together with a shunt resistor of approximately 2 mOhms, but I have a doubt, the current consumed by the peltier it is pulsing and I am not sure what type of output the INA280A4IDCKR will have in this situation,
Can you help me please? , can I use this chip in the application that I have?


I also thought of using a TMCS1108A1UQDT, but I don't know which of these chips can help me

Thanks for the help.

  • 0
    Guru 140200 points

    Hi Martin,

    so the first step is to find out how the current of Peltier cell is behaving. Have you already probed this current?

    Also, what is the PWM frequency?

    Kai

  • 0 in reply to kai klaas69
    Intellectual 270 points

    hello,

    I did some measurements only with a multimeter and it seems to be a normal direct current, without spikes or strange behavior, since the peltier cell is made of semiconductors, I suppose that the current inside it will be the same as in an electrical resistance. The problem I have is that I have a feeling and I am very sure that the current through the peltier cell will be a square wave at a frequency of 5KHz, the PWM works at a frequency of 5KHz, and I do not know how the chips that I want to use behave when the current is a pulsating square signal The PWM frequency is 5KHz and the load voltage (Vbus) is 24Vdc.

  • 0 in reply to Martin Holguin
    TI__Mastermind 27380 points

    Hi Martin,

    The square current will present itself as a square differential voltage to the amplifier, and it is not a problem.  

    If I understand correctly, the goal is to have the ability to drive the Peltier cell in either forward or reverse polarity. If so you probably want to use a current sense amplifier that is bidirectional and capable of working with common mode voltages including ground or lower.

    I would suggest INA240, or INA241 (in preview mode).

    Regards, Guang

  • 0 in reply to Guang Zhou
    Intellectual 270 points

    Perfect, you just solved my question and you also helped me prevent a design error, I will probably use the INA240 since I can get it on mouser, excellent, I only have two more questions.
    So at the output of the amplifier the voltage will be a square wave? and the other question, I want to be able to have an LC or RC filter at the output of the INA240, what values ​​of the filter components would be recommended or what cutoff frequency should the filter have?


    Thanks for the help

  • +1 in reply to Martin Holguin
    TI__Mastermind 27380 points

    Hi Martin,

    The square input will cause a square output ideally, but with practical limitations of course.

    An RC filter is usually found at the output. As long the resistor is 150Ohm or larger, the capacitor can take on any value and it will be stable. So there is great flexibility in setting the cutoff frequency. The lower the cutoff frequency, the more the output will resemble a trapezoid instead of a square. In a first try, I would set it at somewhere between 100KHz and 200KHz.

    Regards, Guang

  • 0 in reply to Guang Zhou
    Intellectual 270 points

    Thank you very much, I will follow your advice