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TMCS1107: Noise at the output of the hall sensor

William Parquette
Prodigy 20 points
Part Number: TMCS1107

I am interested in using the hall-effect current sensor for my design, but I was curious about the noise that can be expected at the Vout pin. I am currently using a GO-10-SME/SP3 hall sensor from LEM and I was seeing significant noise at the output of my sensor (~0.45A). I found that the noise was coming from Uo pin (~27mV) and was getting amplified by my output op amp with a gain of 16.67 V/V giving me a total noise at the output of ~0.45A. When I asked LEM about this, they said this was a trade off of the hall sensor. They said the mechanism (chopping and dechopping stage in the image shown below) that is responsible for reducing error also creates broadband noise. The noise can easily be tamed with a large capacitor, but I feel the noise is too large even without a large capacitor.

I am curious if this can also be expected from your hall sensor. I have also attached a detailed power point if needed. Thank you so much.

  • 0
    TI__Mastermind 18790 points

    William, 

    LEM is correct. Hall sensors are inherently noisy. You should expect to see some noise on our device as well. Here is a scope shot of the TMCS110xA2, full bandwidth, at 0A input: 

    The artefacts you see here are a combination of the noise floor and the sampling integrator the device uses at the end of the AFE. However, the sampling integrator updates at a rate of 250kHz, well above the BW of the device, and similar to the advice provided by LEM, a LPF on the output will often help smooth this noise on larger signals, as shown in figure of the DS:

    How to calculate the magnitude, as well as methods to mitigate this are discussed in depth in our best practices app note located here.