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SN74CBT3257: What's the equivalent circuit of input impedance and output impedance for SN74CBT3257?

user4760726
Intellectual 1185 points
Part Number: SN74CBT3257

Hi team, 

As mentioned in the title, customer would like to know the input impedance and output impedance of SN74CBT3257. Is it possible to provided the related data? Thanks!

Best Regards,

Leroy Song

  • 0
    Guru 243820 points

    S and OE are CMOS inputs; their input impedance is approximately infinite. (If you want a worst-case value, derive it from the leakage current with RI = VI / II.)

    The A and B port pins are not buffered, so they do not really have an input or output impedance. When the switch is on, the connection between A and B behaves like a 5 Ω resistor, but ron increases with the signal voltage.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 23513 points

    Yes, these impedances on S and OE will be effectively infinite. 
    I'm assuming you're more concerned with the A/B ports for impedance and as mentioned above when the switch is on you'll see approx. 5Ω. On open switches ('off' state) they will be Hi-Z. 

    If you're looking for a 4 channel 2:1 with low Ron and Con the TMUX1574 is an updated version of the SN74CBT3257 with improved specs across most features. It's also a pin to pin replacement for TSSOP devices so it's an easy upgrade to make,