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SN74CB3Q16244: does it support hot removal and hot insertion ?

Joyce Li
Intellectual 2170 points
Part Number: SN74CB3Q16244

Hi Dear expert,

My customer wants to know whether SN74CB3Q16244 could support hot removal and hot insertation function?

Can you please help confirm?

thanks very much for your reply in advance.

Joyce

  • 0
    TI__Mastermind 45340 points

    Joyce,

    You will need to be more specific on the application of hot removal and hot insertion because the specs for those events can mean different things from customer to customer.  

    Please see this posting that talks about the different hot insertion terms.

    For SN74CB3Q16244, when Vcc = 0V, the signal path will be in a high impedance state.

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    TI__Intellectual 2170 points

    Hi Adam,

    Thanks for your reply.

    Hot insertion and hot removal in my scenario means the device on the board is subcard, the subcard could be inserted or unplugged to backplane board. Back plane board will provide this subcard power. 

    I reviewed the link you sent in the reply. it is same as below:

    "Usually a card or a board gets inserted on a backplane connector while power is on (what we call live insertion). This means that the device is exposed to many different things which could include signal on the Input pins without power being applied. Also, there could be small transients caused by board parastics during live insertion that could cause latch up if the IC circuit isn't designed for this. A lot of our TCA parts will call out exactly that they can handle this (different functionality though). "

    so the data sheet describes when VCC=0, signal path will be in high impedance, so this mean it could support hot removal. how about hot insertion?

    thanks very much for your reply,

    Joyce.

  • 0 in reply to Joyce Li
    TI__Mastermind 45340 points
    Joyce,

    The SN74CB3QXXXX devices have an internal charge pump that bias the gate of the FET. This FET will not turn on until the Vcc reaches a threshold to power the charge pump. The signal path will remain Hi-Z until the charge pump turns on so if you are pluging the switch into a system that is powered the switches I/O pins will remain Hi-Z until about a 1V when the charge pump will turn on.

    Will this behavior be acceptable in your system?

    Do you see any system issues with an AC signal coupling through the switch I/O path when Vcc = 0V?

    Adam
  • 0 in reply to Adam Torma
    TI__Intellectual 2170 points

    Hi Adam,

    I think this will work for back plan hot removal and hot insertion.

    Thanks very much for your reply!

    Joyce