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TPS55287: Current Limit Control

Paul Barker
Prodigy 265 points
Part Number: TPS55287

Tool/software:

Hello, I've developed a lighting system board and software and have used the TPS55287 to generate an optimized voltage for different use cases.  Everything is working great and have had no major issues.  But I have a quick question about the TPS55287 output current limit control.

From Page 7 of the TPS55287 datasheet if shows 2 different values for the Current Sense Resistor mV/bit, both a value of 30 mV and 50 mV are shown but throughout the rest of the documentation it always shows 50 mV.

However, in my application I have a 10 milliohm current sense resistor and I'm observing a 30mV/bit current limit not the 50mV/bit.  Which one is correct or maybe there are 2 revisions of the IC?

  • 0
    TI__Genius 14960 points

    Hi Paul,

    Thank you for reaching out. There is a register to set the current limit target voltage between the ISP pin and the ISN pin. It means the maximum voltage when output current meets current limit.

    For example, if setting 50mV, and the current sense resistor is 10mohm, when output current is 5A, then the voltage cross the resistor reaches 50mV, current limit will be triggered. if setting 30mV, and the current sense resistor is 10mohm, when output current is 3A, then the voltage cross the resistor reaches 30mV, current limit will be triggered.

    Please check your register value.

    Regards,

    Mulin 

  • 0 in reply to Mulin Yuan
    TI__Prodigy 265 points

    OK, thanks for the clarification.  Even though i'm using 10 milliohm for my current sense resistor, i'm observing a 30mA increase in output current as I change the current limit register value, i think this is because of trace and via resistance on my board that are adding to the 10 mohm creating an effective resistance that is actually higher than 10 milliohms.  I can adjust for this in my code.