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TIC12400: Hybrid wetting mode

Mark Regina
Prodigy 130 points
Part Number: TIC12400


Does TI have an MSDI device that uses a hybrid mode for contact wetting?  My understanding of contact wetting is that it is best to have voltage and current available when the contacts close so that oxidation will be removed.  Continuous mode supplies this, but polling mode may not have the wetting current available when the contacts actually physically close, which may not be an issue if the engineer has absolute control over which switches will be inputs to the system.  Perhaps a hybrid mode would be good (and possibly better than CCP):  any contact that reads as open has its wetting current applied in a continuous manner, then when it detects as closed (after the filtering time) it switches to polled contact wetting, and finally when it next detects as open it reverts back to continuous wetting.  This would yield the lower power benefits of polled mode, yet definitely have the wetting voltage/current available at the moment of contact closure.  Does TI have this in an MSDI device?

  • 0
    TI__Mastermind 34090 points

    We do not have a device with a "hybrid" mode similar to how you have described.  However, I understand your basic desire it to have higher wetting current at the moment the switch is closed in order to burn off any oxide that may have built up, but then reduced wetting current after some amount of time for overall lower device current consumption.

    The Wetting Current Auto-Scaling feature of the TIC12400 sounds like it would accomplish this task.  It applies a larger 10-15mA wetting current initially when it detects the switch has closed, but then it reduces the wetting current to 2mA after the configured number of polling cycles.  This option is only available in Continuous current mode and it won't be as low current as Polling Mode, but it will provide higher current when a switch is closed, and lower current between switching events.  You can find more information about this in the datasheet.

    Regards,

    Jonathan