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TS3L4892: Current flow from unused port

Amarnath Murugadass
Intellectual 480 points
Part Number: TS3L4892
Other Parts Discussed in Thread: DP83620, TS3L501E

Hi Sir/Madam,

What will be the output current  (Ioh/Iol) from the TS3L4892 switch to the connected devices through the selected port (nB1)? What will be current drive through the unused output (nB2) port?

We are using the TS3L4892 in a configuration where the connected device (DP83620) will be in off condition but the TSL4892 will be on but connected to the another port (nB1 connected to RJ45 connector while nB2 will be connected to DP83620; output selected to RJ45 port). We want to ensure that the pins of DP83620 is not damaged due to the leakage current output from TS3L4892. 

Thanks & Regards,

M Amarnath



  • 0
    TI__Mastermind 32883 points

    Hey M,

    The TS3L4892 doesn't drive any current. It's simple a switch that will allow signal to pass through that is applied and within the recommended operating conditions of the device. So the current will mostly depend on the source of the signal that is actually driving the signal. 

    The leakage for the device whether you've selected or deselected the output is listed in the datasheet:



    If you have any unused pins that aren't ever going to be selected, it's best practice to tie these down to GND via a 50ohm resistor.

    We do also have TS3L501E which is a newer device that offers powered off protection, protecting devices downstream even when Vcc = 0 on the 501E.

    Let me know if there's anything else you need,
    Rami

  • 0 in reply to Rami Mooti1
    Intellectual 480 points

    Hey Rami,

    Regarding the leakage current provided in the datasheet (also shared by you in this thread) our understanding is it is for the SEL pin alone and not for the analog input pins.

    Please confirm. 

    Regards,

    M Amarnath

  • 0 in reply to Amarnath Murugadass
    TI__Mastermind 32883 points

    Yes, you are correct in that. This is leakage via the control pins.

    If you're looking for leakage via the I/O pin, the On-leakage which is what you're more specifically looking for(device is on but signal going through it), it isn't spec'ed here. What's the max limit of the DP83620 pin you're inserting this into and how much room do we have to work with given the current signal going in? I can't imagine that the current leakage would impact it much. The device isn't driving any current itself on the I/O and worst case you'll see leakage typically in low uA range. Is the DP pin that sensitive? I've looked through the datasheet and I'm not spotting anything that would indicate it would be a problem but I may have overlooked it.
    If you can provide the numbers on what the max is and how much current you expect to actually be drawn we can analyze this further.

    Thanks,
    Rami