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# TMCS1101: TMCS1101 Maximum current sensing capacity

Part Number: TMCS1101

Dear Expert,

I plan to use the TMCS1101 Current sensor in our Robots which is for 24v and 48v operating. I referred the datasheet but i didn't get the details of maximum current sensing of TCS1101.

• Naveen,

The answer to this question depends on whether you want to know the area the current will be linear, or the maximum amount of continuous current the device can support. The linear measurement region is determined by the chosen sensitivity of the device. The linear range for the bidirectional use case is given in section 5 of the datasheet.

HAs shown in footnote 2 though, these given ranges are bounded by the safe operating area requirement found in section 8:

TThis section and corresponding graph show that the amount of current that can be handled by the package derates with the ambient temperature, and must be taken into account. If your design is intended to operate in 125C environments, then it is recommended that the maximum continuous current through the device not exceed 15A.

• Dear sir,

What is the difference between unipolar and Bipolar and I didn't understand about  -2.8A-->27.7A. what is the negative -2.8A here.

• Naveen,

Unipolar versus bipolar (unidirectional vs. bidirectional) is in reference to whether you are trying to measure current in a single direction, or in both directions. The chart above provides linear ranges for both cases .5*Vs ('B' devices) for the bidirectional, and .1*Vs ('U' devices) for the unidirectional. The reasons for these reference points is discussed in section 8.1.2 of the datasheet. The case you call out here is looking at unidirectional measurement, with a .1*Vs internal reference, with Vs = 3.3V, for the A2 variant device. This means the reference is set at .33V, and the sensitivity of the device is 100mV/A. The chart shows that the device can linearly measure up to 27.7A, which brings the voltage up to 3.1V, taking into account swing limitations of the output stage, but as I mention in my first post, care must be taken at this range as the maximum current through the device is temperature dependent.

Let me know if this makes sense.