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TMUX8212: TMUX8212 Enable and Disable Timing

Zoltan Bardos
Prodigy 20 points
Part Number: TMUX8212
Other Parts Discussed in Thread: TMUX8213, TMUX8211

Hello,

I am looking for clarification on the language used in the datasheet for TMUX821x. I am using the TMUX8212 variant, which is the normally open version.

I am trying to understand the time from the "SEL" signal going high, to the switch closing (opposite of the default state). In table 9-2 this is called "Channel ON".

Then in Figure 8-4 we see the following set up, and language that implies that the parameter "t_on" is the time to output change after the FALLING edge of the "SEL" signal, and therefore the time to return to default state.

Here are the timing characteristics from section 7.13:

My final conclusion is that for TMUX8212 Normally Open variant, the timing characteristics as seen in section 7.13 can be described as follows:

- tON (EN) = 4us typ. = the time for the switch to open (return to default state).
- tOFF (EN) = 100ns typ. = the time for the switch to close.


Is my understanding correct?


Thanks for your help!

  • 0
    Guru 278840 points

    The three TMUX821x variants share a datasheet. The text in section 8.4  says:

    Turn-On time (tON) is defined as the time taken by the output of the TMUX8211, TMUX8212, and TMUX8213 to rise to a 90% final value after the SELx signal has risen (for NC switches) or fallen (for NO switches) to a 50% final value.

    Figure 8-4 shows the SEL signal of a NC switch. For a NO switch, you would have to invert it.

  • 0 in reply to Clemens Ladisch
    Prodigy 20 points

    Is it indicated somewhere that the figure 8-4 is for a NC switch?

    This sentence in section 8.4 is the source of my confusion.

    In the diagram, the output is pulled low with a resistor RL. In order for the output to rise to a 90% final value, the switch needs to be closed! This would correspond to a logical 1 on the SELx signal for a NO switch right? That is backwards to what the text suggests. How does a rising output correspond to a falling SELx signal for NO switches?

    I am going through all the trouble to clarify this because switch timing is very important for my application. I need to confirm the correct behavior described by the t_on and t_off parameters.

    Thanks!

  • +1 in reply to Zoltan Bardos
    Guru 278840 points

    The text indeed is wrong. For a NO switch, a rising edge on SEL closes the switch.

    Anyway, the switching time is the same for all TMUX821x variants, and tON is for the switch closing, and is the slower one.

  • 0 in reply to Clemens Ladisch
    Prodigy 20 points

    Thank you for confirming I am not crazy :)