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TS12A44513: What happens if we lose the supply voltage?

Enzo Illiano
Prodigy 110 points
Part Number: TS12A44513
Other Parts Discussed in Thread: SN74CB3Q3125

What happens if we lose the supply voltage? Are the contacts normally open or normally closed? In other words normally closed or normally open is just an inversion of the required driving signal or it also impacts the default condition of the switches when the IC has no supply?

Do you have the same or a similar device with higher ESD ratings?

Thank you

Enzo

 

  • 0
    TI__Mastermind 45370 points

    Enzo,

    The TS12A44513 is not a mechanical switch so there are not any physically moving parts that will contact pads.  The devices is a solid state switch and the terms normally closed and normally open are borrowed from the mechanical switches but are not accurate.  The better words to use will be conducting (FET is ON) or not conduction (FET is off).

    The TS12A44153 does not have the powered off protection feature so there is no defined state of the signal path when Vcc = 0 V or looses supply voltage.  Devices with the powered off protection feature will have a defined Hi-Z state when Vcc = 0V.  There will be a leakage specified in the datasheet under the powered off condition like in the SN74CB3Q3125.

    You can use the switch search tool on TI.com for some help finding devices with this feature but the tool isn't perfect yet as I have already caught an error.

    Let me know if that makes it more clear on what happens to solid state FET switches when Vcc = 0V.  You can also look at the frequently asked question page for some more information on solid state FET switches.

    Thank you,

    Adam

     

  • 0 in reply to Adam Torma
    Prodigy 110 points
    Dear Adam,

    Thank you for your quick and exaustive answer. Concerning ESD do you have devices which have higher values? Or do you suggest maybe to use a protection circuit (like for example two diodes connected to GND and VCC at each input)?
  • 0 in reply to Enzo Illiano
    TI__Mastermind 45370 points

    Enzo,

    I was so busy with the first part I forgot the second part about ESD.  You may use the switch search tool to look at the ESD ratings of the devices and sort them greatest to least.   

    Yes you may also use external protection diodes which is a common practice by our customers for added protection.

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    Prodigy 110 points

    Dear Adam,

    Thank you.

    We are concerned about safety:) So in case of falilure (for example over current or over voltage, ESD,..) there is the risk of a short between the load side and GND right? In other words this device does not guarantee the same safety level (regarding this point) of a conventional signal relay where a short between load and control coil is basically an impossible event?

    Best 

    Enzo

  • 0 in reply to Enzo Illiano
    TI__Mastermind 45370 points

    Enzo,

    If a solid state switch sees an ESD, over voltage, or over current event that is outside the absolute maximum specification there can be no guarantee the performance of the silicon.  The failing performance could be as benign as shift in parametric performance or as sever as an open or short circuit but there can be no guarantee if the IC is exposed out side of its maximum specification what type of damage can occur.   

    If you are concerned about a solid state switch being exposed to an event outside of the absolute maximum ratings and cannot have the potential failure be a short between two pins then I think you will need to go with a different technology like a mechanical relay where the piece of metal can fall away from the contacts to ensure an open circuit.

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    Prodigy 110 points

     Dear Adam,

    Thank you for your answer.

    Can you offer devices with a defined state even if VCC is lost (like the SN74CB3Q3125) but with at least 12 V supply?

    I couldn't find any component but maybe I missed something.

    Best regards

  • 0 in reply to Enzo Illiano
    TI__Mastermind 45370 points

    Enzo,

    You are not missing anything to my knowledge.  As you probably found that many of the devices are over 15 years old.  Please expect our new devices coming out next year to have these features defined in the datasheet.

    Thank you,

    Adam