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bidirectional current sensing?

Sangkyu Kim
Intellectual 290 points
Other Parts Discussed in Thread: INA381, INA193, INA200, LMP8601, INA282, INA206, TMCS1100

Hi,

I design Pulse generation circuit using Op-amp.

Without current sensing amp(INA381), the output signal is no problem.

But, add current sensing amp(INA381), Output signal is clamping under 0V.(Not output negative voltage).

What is the problem?

INA381 is not supported negative direction current?

Do I choose other current sensing amp?

  • 0
    TI__Mastermind 29680 points

    Hi,

    The common mode input range of INA381 (-0.3V, 26V) puts a limit on the amplitude of the pulse. If the pulse attempts to go below -0.3V, it will be clamped by INA381. Further, if the buffer amplifier is capable of sinking large current, INA381 could be damaged.

    We have a few shunt based devices that can accommodate -15V common mode voltage, examples include the following families: INA193, INA282, INA200(with comparator), INA206(with comparator), LMP8601. Theoretically the common mode voltage can be full ±22V provided by the buffer. I would select one that is capable of accepting this voltage range for long term reliability. We also have isolated current sensors such as the TMCS1100 family.

    It appears the current you’re measuring is rather small. It may pose a challenge in terms accuracy, 

    Regards, Guang