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TMCS1101EVM: Getting 10mA resolution on a 1A, 100us pulse

Part Number: TMCS1101EVM
Other Parts Discussed in Thread: TMCS1101

TMCS1101EVM, 5V supply.

Customer trying to get measurements with 10mA resolution, on a 1A, 100usec pulse. However, it was observed that the noise level was close to 100mA range.

Is this the expected performance of TMCS1101?

Waveform capture available via email.

  • Eddie,

    There's not a lot of information here to say with certainty, but the answer to your question is "maybe." Is the customer referring to RMS noise, or peak to peak here? While I wouldn't expect the RMS floor to be quite this high, the peak to peak values could potentially be this high, IF the full BW of the device is being used, and/or a higher GAIN variant is being used here. 

    Hall effect sensors are inherently noisy, and are usually not intended for precision measurements, so this could indeed be the case. Can you share which gain variant from the EVM the customer is using here, because that will have bearing on the intended noise here. Here are the spectral densities by GAIN:

    Assuming the customer is utilizing the full BW of the device, we can then look at the noise contribution from the above densities, referred to the output as the following table:

    So as you can see, I would not expect any of the devices to exhibit 100mV of noise from an RMS perspective, but I would expect variants A3 and A4 to exhibit this from a peak to peak perspective. 

    The takeaway here is that unfortunately, Hall effect devices are most likely not going to be the ideal solution for such a use case. Is there a reason they matriculated toward such a solution? Do they require isolation in the application?

  • Agree and proposed other current sense amps to customer.