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TMUX1109: Drop-in replacement for TMUX1209

Dimitar Valkov
Prodigy 10 points
Part Number: TMUX1109
Other Parts Discussed in Thread: TMUX1209

Hi,

I have a PCB designed for TMUX1209PWR, but it is currently "out of stock" at pretty much any distributor I could find. According to the website TMUX1109 is a "drop-in replacement" for the chip. What bothers me, is that pin 3 is "nc" on TMUX1209, but Vss on TMUX1109, and using TMUX1109 with my PCB will leave the Vss pin floating. Thus, is there anything internally in TMUX1109 that allows it to be used with a floating Vss pin?

Thanks in advance for the help,

- d 

  • +1
    TI__Guru 51882 points

    Hi Dimitar,

    Your intuition would be correct - you can't leave the VSS pin floating on the TMUX1109 as its a power rail and in single sided applications it needs to be grounded.

    I know that is confusing as the cross reference tool says its a drop in replacement, but I think that may just be a small mistake. The reason behind that is most likely due to the fact that the 1209 can replace the 1109 in most applications , as the 1109 is still mainly used in single sided applications and grounding the N.C. Pin on the TMUX1209 isn't an issue.

    This is still the closest part we have to a drop in replacement - but VSS would have to be grounded first or else most of the operation of the multiplexer will be undefined. 

    Please let me know if you have any other questions!

    Best,

    Parker Dodson 

  • 0 in reply to Parker Dodson
    Prodigy 10 points

    Hi Parker,

    thanks, this really helped.

    Parker Dodson said:
    grounding the N.C. Pin on the TMUX1209 isn't an issue

    maybe adding this in the next revision of the datasheet (and in the cross-ref tool) is a good idea... just to ensure compatibility in the PCB design.

    Thanks again & Best Regards,

    - dimitar