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TMUX1308-Q1: current injection control

Dierk Bronner
Intellectual 1460 points
Part Number: TMUX1308-Q1

Tool/software:

Dear MUX experts,

my customer is using TMUX1308-Q1 in one of his designs.

Now we have a question about the effect of the injection control on the input signal.

Our circuit looks similar to the one in the data sheet, but with an additional capacitor:

If we now feed in a signal that is higher than Vdd, what is the voltage at the input?

Can we assume that the injection control behaves like a diode to Vdd? In other words, the signal is stabilized at approx. Vdd+ 0.4V and the injection control MOSFET behaves like a resistor?

Or is it the case that when Vdd is exceeded, the signal is first connected hard to GND?

Kind regards

Dierk Bronner | Senior FAE Automotive

  • 0
    TI__Expert 6685 points

    Hello Dierk,

    Today is a TI Holiday, please expect a delayed response.

    Thanks,

    Nir 

  • 0
    TI__Expert 6685 points

    Hello Dierk,

    The voltage on the input will be 5 to 6V. In context of your question, the injection current control behaves more like diode to GND. 

    Please see attached explanation from the datasheet.

    Thanks,

    Nir 

  • 0 in reply to Nir Gilgur
    TI__Intellectual 1460 points

    Hi Nir,

    thanks for the feedback.

    What my customer understand now: the voltage will be between 5V and 6V, but the current will be diverted to GND.

    What is a bit misleading is "...behaves like a diode to GND..." But that should probably mean "...behaves like a diode to Vcc"

    can you comment on this please

    Dierk Bronner | Senior FAE Automotive

  • 0 in reply to Dierk Bronner
    TI__Expert 6685 points

    Hello Dierk,

    I apologize for the confusion, but the injection current control uses a FET to GND. It actively pulls undesired current to ground.

    It is more of a dynamic mechanism and controlled vs a simple diode. 

    The injection current control doesn't use a diode, so can you please explain to what do you mean by "behaves like a diode to Vcc"

    Thanks,

    Nir 

  • 0 in reply to Nir Gilgur
    Prodigy 10 points

    Sorry, I accidentally created a new thread. Here the input to that thread

    Hello

    I am asking this question as we still can not understand the exact working for this injection control if the voltage is higher than Vdd.

    It has been mentioned that the voltage in this overvoltage event will be between 5 and 6 V, so to the outside it looks like a diode to V.

    Of course, the current will be shunted to ground instead of to Vdd.

    In short, there is a FET acting in linear mode to ground with a max. capacity of 50mA?

    Thanks and Regards

    Joachim

  • 0 in reply to Joachim Neubert
    TI__Expert 6685 points

    Hello Joachim,

    That is correct, essentially it behaves as a FET to ground. The capacity of the FET is 100 mA for one channel. 

    If all 8 channels have an injected current event then the capacity will be 100/8 mA. 

    Please see table below:

    Thanks,

    Nir