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TS5A26542 Application Question

TS5A26542 Application Question

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David Escandon
Posted by
on Apr 05 2012 17:42 PM
Expert2155 points

TI Team,

I would like to get some clarification about the TS5A26542 SPDT analog multiplexer. The datasheet is not clear about the conditions under which a switch pin is left unconnected. Here are my queestions:

Questions:

  • According to the datasheet, the VIO logic supply operation rate is from 1.65v-1.95v but its absolute maximum rating is 6.5v. I was wondering what would be the disadvantages of connecting the VIO to 2.2V supply? would it affect device reliability or performance? Our V+ max supply is 5.5V. The datasheet says you can connect this pin to a higher voltage as long as you don't exceed the input-clamp current. How do you calculate the threshold?
  • Based on design I need to use only one of the NC or NO pins for each switch, is it okay to leave either not connected or should I tied it back to output. It's usually customary to pullup or pulldown unconnected pins. What is your opinion for this switch line?
  • 3. What is the maximum leakage through the switch and would it be different on NO, NC and COM pins? (assuming NC floating(not connected), and logic low for NO connection (but having high voltage on NO pin)). Although the datasheet specifies a maximum current of 100nA, will this apply if either the NC or NO is left floating. Again, this comes back to my first question.

-David

Unconnected Pins TS5A26542 CMOS Multiplexers
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  • Eric Nachtigal
    Posted by
    on May 03 2012 11:46 AM
    Prodigy450 points

    David,

    1.) I spoke with one of our designers, he took a look at the device and sent this in reply: "I don't see any major concerns with Vio=2.2V.  ... The only current consumption increase would be if the customer did not drive the input to the 2.2V rail, but to a lower “high” voltage."

    As per the datasheet the triggering voltages will be:

    • .65 x Vio for Logic High min threshold
    • .35 x Vio for Logic Low max threshold

    We can not 100% guarantee long term stability of the device under these conditions. However talking with the design engineers, it seems that there should only be a minimal extra current draw and no long term damage from regularly operating this device at Vio=2.2V. Hope this helps!

    2.) Any unused NO, NC or COM pins on this switch should be pulled down to ground with a 1k-10k resistor.

    3.)Could you please clarify your question. As it stands all of the NO,NC,COM leakage currents are currently listed in the datasheet on page 4 for 5.5V V+

    Regards,

    Eric Nachtigal

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  • David Escandon
    Posted by
    on May 03 2012 18:57 PM
    Expert2155 points

    Eric,

    Thanks for responding to my post.

    In regards to question 3, I want to know if the leakage current number will (100nA) change if either the NC or NO is left floating. 

    -David

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  • Eric Nachtigal
    Posted by
    on May 10 2012 19:10 PM
    Prodigy450 points

    David,

    We recommend using a 10k resistor to ground on all unused NC or NO pins. Leaving the pin floating should have no affect on the leakage current and in some cases can cause instability or even damage in the device.

    Regards,

    Eric

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