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Captivate: Maximum high Noise immunity level upto 30V

Patrick Verkennis
Expert 4290 points
Other Parts Discussed in Thread: TIDM-CAPTOUCHEMCREF

Hi Champs,

Customer was checking TI website for latest info on Captivate technology, and has seen a lot more info is now available. Customer projects requires(with most of time) (very) high noise immunity needs. Customer was wondering if TI already challenged this solution to the edge?

best possible Captivate performance reported in documentation/testreport:

Class A Immunity Table (Fully Functional in Presence of Noise)

Sensing Method

Sensor Type

Achievable IEC 61000-4-6(Conducted) Level

Self

Buttons

Level 3 (10V RMS)

Self

Sliders/Wheels

Level 3 (10V RMS)

 

Customer questions:

Which maximum level could be achieved above 10Vrms ?   Some clients are asking for higher immunity (for example up to 30V rms), but we would like to know what could be achieved and seen as really the maximum possible with captivate technology.

Are there test results available above 10Vrms (on certain evaluation setup, certain devices?)

Thanks in advance, Patrick

  • 0
    TI__Expert 7530 points

    Hi Patrick,

    Thanks for asking this, it's a great question.  Ultimately what is achievable comes down to the system design.  3Vrms is achievable for the majority of applications.  Going up to 10Vrms requires careful attention to detail.  It is possible to take a design above 10Vrms, but the extent to which this is achievable really comes down to what the HMI requirements are and what can be done at the system level. 

    For example, 10Vrms and 10Vrms+ is much easier to achieve for a simple design with 1-4 buttons, a reasonable overlay material thickness (<3mm), and a decent power supply with common mode filtering than it would be for a design that required 16 buttons, a thick overlay/air gap, and a poor power supply.  With fewer channels and good overlay design, oversampling can be applied much more effectively while still achieving a decent report rate.  Common mode chokes can be applied to attenuate common mode noise currents before they enter the system power supply in the first place.

    The TIDM-CAPTOUCHEMCREF reference design can be used as a starting point to see how noise immunity is improved with different power supply configurations.  For this design we internally tested up to 10Vrms for full touch functionality and up to 20Vrms for no false touch detection (the panel does not false-trigger when idle and exposed to 20Vrms conducted noise).

    Are you looking to implement a complex HMI with a challenging stackup, or something simple?

    Regards,
    Walter

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