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TMUX1308-Q1: RLIM resister for injection current control

Hidekazu Someno
Expert 5130 points
Part Number: TMUX1308-Q1

Hi; Team,

This part has an injection current control.

When Sx or D of disable switch is >VDD or <GND, the injection control circuitry clamps by shunting the voltage to GND.　

However, from the data sheet description, the injection current per input terminal should be limited to <50mA and the total injection current for all disable switches should be <100mA in this situation.　And To meet the limitation,  it is recommended to add a series limiting resister(RLIM) in datasheet, figure-15.

What is the method (calculation formula) for obtaining this RLIM resistance value?

Regards,

H.Someno

  • 0
    TI__Guru 52432 points

    Hi Hidekazu,

    Based on the maximum injection current into an off switch, the formula for Rlim is:

    Rlim = Vin / 50mA - this is for the situation for one input.

    However since there could be multiple off ports that have current injected into them the second parameter is going to come into play. That is the 100mA max. This is shown below:

    100mA >= I_inj0 + I_inj1 + ... + I_injN

    100mA >= Vin0/Rlim0 + Vin1/Rlim1 + ... + VinN/RlimN - Each Entry represents a switch input where the switch is in the open position. 

     

    N Represents the total number of ports that are off. The device can only take a maximum injection current input of 100mA.

    This TI Precision Lab Video explains it more detail.

    Best Regards,

    Parker Dodson