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TMUX7212: TMUX721x switch states

Joe Norris
Prodigy 70 points
Part Number: TMUX7212

Hi,

In order to answer my technical question, I tried to run TI-PSPICE with the TMUX7212 sample schematic/simulation, but was getting errors "out of the box".   I could not fix these errors (which were apparently due to paths not found), so I need to ask the knowledgeable engineer there at TI:

1) The operational diagrams on page 1 of the attached datasheet suggest that, specifically for the TMUX7212, the SW switches are "closed" (ie, conductive of around 2 ohms) when the corresponding SELx = logic 1.  Correct?

2) The Pin functions definition table (ie, Table 6-1 on page 3) suggests there is a Pulldown on each SELx line.   Meaning that if the SELx is left "unconnected", driven low, or "driven" by a tristate, the corresponding SW will be "open".  Correct?  This appears to be consistent with the 9-2 Truth Table on page 28.

3) What is the state of the SW's if the TMUX7212 is not powered (ie, VDD/VSS is set to 0 volts)?   In this power-off condition, can the chip tolerate voltages applied to the switch I/O (as measured with respect to GND);  Are there parasitic diodes on the I/O of the chip?

Thank You,

Joe Norris

  • 0
    TI__Genius 10974 points

    Hi Joe,

    Can you please provide a schematic of how you are setting up the TMUX7212 model in PSpice and a snapshot of the error you are seeing?

    To answer your other questions, see below:

    1) Yes, you are correct. The TMUX7212 variant will close the switch when a logic high is applied to the SEL pins.

    2) Yes, there is an integrated pull down resistor in the physical device itself to eliminate the possibility of a floating digital pin. However, this is not modeled in the pspice model.

    3) If the TMUX7212 is unpowered, there is a risk of damaging the device when the I/O voltage exceeds the VDD/VSS supplies by more than 0.5V as noted in the abs max table in the datasheet. The reason for this possible damage is due to the ESD diodes present on each I/O pin that will conduct when this condition is met.

    Thanks,

    Bryan

  • 0 in reply to Bryan Marshall
    Prodigy 70 points

    Thank you for your answers to 1) 2) and 3).   Regarding simulation, I downloaded the current version of TI-Spice then downloaded the TMUX7212 model, which included a schematic.  When I hit the "run" button, I got an error, but don't have time to fix it.   I'll go with your written answer(s) above!

    Thank You,   Joe Norris

  • 0 in reply to Joe Norris
    TI__Genius 10974 points

    Hi Joe,

    No problem! I will investigate the default schematic on the model and see if I can find anything. Apologize for the inconvenience.

    Thanks!

    Bryan