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TMCS1100: What if TI TMCS compared with AMCX3XX isolated amp solution?

user4811888
Intellectual 530 points
Part Number: TMCS1100
Other Parts Discussed in Thread: AMC3302

Hi TI expert,

I have found below paper comparing TI AMC3302 shunt-based scheme with hall-based CLCS(closed-loop current sensor) solution.

https://www.ti.com/lit/pdf/sbaa464

The result shows AMC3302 beats hall-based CLCs completely, could I learn that the hall-based CLCS representing TMCSxxx product as they're actually hall-based?

If NOT, what's the pros and cons when TMCSxxx are put together with AMCxxx? Thanks!

  • 0
    TI__Mastermind 18780 points

    Dear user,

    It is true that typically shunt based solutions will provide a more accurate result than Hall based sensors. The TMCS family improves on this with its "zero-drift" technology, but even then you can see from the datasheet that the typical sensitivity would be around the 0.5% exhibited in the paper you show. Some improvement in performance may be seen if you look at the typical value as is examined in this paper.

    However, there are several aspects that still make Hall sensors attractive, mainly from an implementation and cost standpoint. Note that for the paper you link, 2 IC's, a 20W (expensive) precision shunt, and 12 passives are required to generate the accuracy the paper presents. We have a second document that discusses some of the tradeoffs at a general level, and I would advise you to check out this application note that discusses the tradeoffs from a cost vs. accuracy perspective. You can change out the parameters from the TMCS110x to see an apples to apples comparison. 

  • 0 in reply to Carolus Andrews
    Intellectual 530 points

    Got it, thanks very much! 

    Very nice paper and i would go through it.

  • 0 in reply to Carolus Andrews
    Intellectual 530 points

    Hi Carolus,

    One more question, I have noticed one statement in the paper you offered, that is "open-loop" hall sensor, which is claimed "closed-loop" CLCS in another paper.

    TMCS family should be "open-loop" hall sensors with accuracy improving techniques like zero-drift, right?

    If so, what is "closed-loop" hall sensor mentioned in another paper?

  • 0 in reply to user4811888
    TI__Mastermind 18780 points

    Dear user, 

    Yes, the TMCS110x family of products are open loop hall sensors in that the device simply amplifies the detected signal by a given sensitivity and drives the result on the output of the device. 

    Closed loop Hall sensors do esxist, and it looks as though this was the form of device placed competed with in the above paper. Closed loop sensors use the generated Hall measurement to create a correction current and effectively drives a coil to zero, which provides many benefits including cancellation of drift. The general consensus is that CL Hall sensors are more accurate than their open-loop counterparts, but the market is wild with innovation at the moment, so make sure to do due diligence on the devices you examine. This makes sense now as to why the paper stated space reduction, as the devices they were examining would either need a coil to drive, or would be in module form which integrates the coil into the package. 

    For a much more thorough explanation, this little site does a great job of laying out the two types of Hall strategies.