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TMUX1308-Q1: Injection Current

Michael Daimer
Intellectual 1745 points
Part Number: TMUX1308-Q1

Hello,

I have some questions regarding the injection current of the TMUX1308-Q1.

1. With reference to Figure 15 (Page 17) & Table in chapter 7.3 (Page 4) in Datasheet, can we exceed voltage on Input Pin to any voltage > VDD (In our case VDD=5V) as long as the Injection current per pin is limited with RLIM to < 50mA ?

2. if we apply ±40V at the Input pin with a series resistor 464kΩ (with VDD = 5V), the injection current through the pin can be ±86.2µA (< ±50mA specified). Will this have any influence to device functionality or Lifetime ?

3. Do we need any additional protection circuit other than RLIM to handle ±40V at the input pin (with VDD=5V) ?

4. What suggestions or recommendations do you have for using TMUX1308-Q1 under these conditions?

Please let me know, in case you need some additional information.

Thanks in advance and best regards,

Michael

  • 0
    TI__Guru 52462 points

    Hi Michael,

    1. Yes, in the case of an over-voltage event if the current is limited to keep the current within the absolute maximum ratings it should be fine, however typically we don't see people over-volting the part by that wide of a margin. Can I ask why you are using a low voltage multiplexer in this scenario?

    2. Running parts near abs max, or in this case - overvolting the parts can cause the lifetime of the part to decrease because of a more extreme use scenario.

    3. The high voltage that the switch may encounter - considering you wont be passing that through the circuit - I'd honestly suggest a TVS diode to suppress those high transients, and if the voltage still is a bit above abs max, since TVS diodes aren't exact, you can decrease the resistor size. I honestly think that would decrease the chances of possible issues by running the voltage so high.

    4. If you need to use the TMUX1308-Q1 in this scenario I would add a TVS diode and a current limiting resistor if the TVS diode clamps a bit above/bit below the abs max voltage level to ensure current limiting. 

    Please let me know the application if you can because while you can get a system like this to work I am not 100% if the 1308 is going to be the best fit.

    Please let me know!

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    TI__Intellectual 1745 points

    Hi Parker,

    thanks for your fast response and the good answers.

    One last question: 

    In case one input of the MUX gets current injected as described above, how does it influence the other channels? Would e.g. the GND of Vcc voltage be shifted?

    Best regards,

    Michael