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Original question:

TPS27S100: Current limiting application

TPS27S100: Choosing Rimon Value

TRM
Intellectual 1785 points
Part Number: TPS27S100

Hi,

I have a customer that is looking to use the TPS27S100B and we want to make sure that R_imon is set correctly. 

They want to use R_ilm as a backup, so they have it set to 510 ohms which should correlate to ~4.8A.

They want to monitor the current via a 3.3V ADC and turn off the output via the enable pin if the current exceeds 4.5A

Equation [1] in the datasheet shows the R_imon = (V_imon * k_imon) / I_out ... since k_imon is set to 500, setting V_imon to 3.3 V and I_out to 5A (to give some margin) provides a value of 330 ohms for R_imon. Does that seem correct or is there something that I am missing?

Thanks

-Tyler

 

  • 0
    TI__Genius 12410 points

    Tyler,

    This math is correct. However I would say that a more reliable method of having a current limit would be to set the current limit to that value. The device will not shut off when it hits current limit but it will keep it at that value and output a FLT value on the IMON pin of 5V.

    Also you will need to make sure your ADC will not see this fault voltage if it is not rated for it. You can do this by resistor dividing the IMON output to go into the ADC.