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TIC12400: TIC12400QDCPRQ1

SS C
Prodigy 30 points
Part Number: TIC12400

Tool/software:

Hello,

I would like to program an input to deteciton as both switch-to-battery and switch-to-ground while also detecting wire break, short-to-ground, and short-to-battery faults. Is it possible to achieve this?

Can you assist me with this issue?

Thank you,
Regards.

  • 0
    TI__Mastermind 33140 points

    Hello SS C,

    The TIC12400-Q1 has current source (CSO) circuits for all 24 INx pins (IN0 to IN23) which are generally used for switch-to-ground configurations. 

    Only 10 INx pins (IN0 to IN9) have current sink (CSI) circuits which are generally used for switch-to-battery configurations.

    Only one of the current source or sink options is available for an INx pin at a time.  Therefore, the device can configure either the CSO or CSI for an INx pin, but not both at the same time.

    The CSO and CSI circuits function more like current limiting circuits and when enabled, they provide a low impedance path between the INx pin and either the VS supply pin for CSO mode, or to GND for CSI mode.  The actual current level will depend on the resistive load outside of the TIC12400-Q1. 

    If the current from the external load will result in a larger current than is set by the wetting current limit configuration (0, 1, 2, 5, 10, or 15mA), then the device will limit the current to this set level.  For example when a switch is closed, this will be a low resistance and the wetting current will be limited by the device.

    If the switch is open, this presents a high resistance path and very little current will flow (based on Ohm's law v=I*R) because both the voltage and resistance are fixed by the battery and physical resistance.

    The TIC12400-Q1 has an internal digital comparator that can be used to detect whether the INx pin voltage is above or below a configurable threshold (2, 2.7, 3, or 4V).  This may be enough for switch status, but it is not good enough for fault detection.

    The 10-bit ADC is more useful for fault detection because it allows you to read the raw ADC code for the INx pin and calculate an exact voltage between the range of 0V and 6V.  If the amount of external resistance changes between a normally open/closed switch and one of your fault conditions, then the ADC value could in theory be used to detect this type of fault condition based on calculations run on the raw ADC code.

    But there are no internal native fault detection registers in the device, and you will need to determine whether there is a fault condition based on the normal operation of the device.

    For a better overview of how the device can be configured, please review the Steps to Configure TIC12400-Q1 Multiple Switch Detection Interface (MSDI) Application Report (Link).

    Regards,

    Jonathan