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Original question:

TMUX1208: Issues with possible interference or powering off?

TMUX1108: Not able to drive VCC power.

Cho
Prodigy 80 points
Part Number: TMUX1108
Other Parts Discussed in Thread: TMUX1308, TMUX1208, TMUX1574, TS3A44159, TS3A5223

I have a modem that sends a 1.8v (USIM_VDD) to a card. I am using the TMUX1108 to powered by 5v to switch between 8 cards. It works but it will cause the modem to turn off after 2 hours. The modem turns off when it detects there is an issue supplying power to the card to prevent damage to the card. There are CLK,IO and RST lines but those are working fine with TMUX1308.


I tried the TMUX1208 as well with no anvil.

The TMUX1574 worked perfectly for my use case but it only has 1:2 for 4 channels. I am open to trying out new chips, for example anything that is 1:8 for 1 channel will suffice.

  • 0
    Guru 283290 points

    The TMUX1108 already is the 1:8 switch with the lowest resistance.

    What peak current do you need to support?

  • 0
    TI__Genius 10552 points

    Hi Cho,

    Clemens is correct here with TMUX1108 already being our lowest resistance offering for this configuration. I assume you mean the modem turning off after 2 hours is unintentional? 

  • 0 in reply to Alex Vish
    Prodigy 80 points

    Correct, it shouldn't be turning off. It works fine if I hardwire the modem's USIM_VDD line to the card directly. So I'm suspecting it's an issue with the mux. There was a typo, the USIM_VDD supplied by the modem is actually 1.8v.

  • 0 in reply to Cho
    Guru 283290 points

    You could use multiple TMUX1108 in parallel, or create a 1:8 circuit with multiple smaller switches like the TS3A5223 or TS3A44159.

  • 0 in reply to Clemens Ladisch
    TI__Genius 10552 points

    Hi Cho,

    Is it possible to implement a solution like Clemens suggested so you can keep utilizing a part that works for your application? Stringing multiple 1108's in parallel would be ideal here before exploring other smaller switches. 

    Regards,
    Alex

  • 0 in reply to Clemens Ladisch
    Prodigy 80 points

    The TMUX1108 is still causing the modem to turn off. I'm using the TMUX1108 to feed USIM_VDD (power provided by the modem to card). 

    To rule out the TMUX1108 being the issue, I used a breakout board where I hardwire the USIM_VDD connection to the card reader which bypasses the TMUX1108 and it stays on as it should.

    The TMUX1574 has worked for me in the past but my client requirements have changed. I need something that is 1 channel but 8 outputs. I noticed the RON on the 1574 & 1108 are not too far apart. Is there anything else I could be overlooking when selecting a chip?

  • 0 in reply to Alex Vish
    Prodigy 80 points

    Hi Alex,

    I have a breakout board for the TMUX1108, I will try running them all in parallel and report back shortly. I am using the TMUX1308 chip for my USIM_CLK, USIM_IO, USIM_RST lines. The TMUX1108 switches the power provided by the modem to the card reader pin (USIM_VDD).

  • 0 in reply to Cho
    TI__Genius 10552 points

    Hi Cho,

    Thanks for the feedback. Do let me know about the results. 

    As for what could possibly be over looked - the TMUX1574 has powered off protection while the other devices here do not. This feature up to 3.6 V on the signal path of the TMUX1574 provides isolation when the supply voltage is removed (VDD = 0 V). When the TMUX1574 is powered-off, the I/Os of the device remain in a high-Z state. If you have a situation where supply is possibly being removed then this might explain the difference between TMUX1574 working while the others do not. 

    Regards,

    Alex

  • 0 in reply to Alex Vish
    Prodigy 80 points

    That is great advice. I overlooked the powered off protection.

  • 0 in reply to Cho
    TI__Genius 10552 points

    Hi Cho,

    Good to know. I'll close the thread for now. Let me know if anything else is needed!

    Regards,

    Alex