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Original question:

TPS40210: TPS40210 keeps resetting while there is no overcurrent event

TPS40210: RISNS value

Henry Wang3
Genius 3355 points
Part Number: TPS40210

Dear Sirs,

As I know the equation 49 on TPS40210 datasheet, it is let me calculate the maximum value of RISNS on Visns(OC)min at 120mV. 

My customer would like to know what is the condition, and they need to calculate the RISNS value on equation 50. could you please help us to explain this question?

  • 0
    TI__Guru 65550 points

    Hello Henry,

    Please excuse me, but I do not understand what needs to be explained. The customer needs to enter the values of his design and make sure that the sense resistor is below both results.

  • 0 in reply to Brigitte
    Genius 3355 points

    Dear Sir,

    My customer designed the TPS40210 schematics show as below.

    and they used the inductor parameters show as below.


    The figure-1 is shown for 5Vin to 48Vout/Iout 0.15A nonsynchronous boost regulator, and they selected the RISNS(R577)=120 Ohm, when output current=80mA, the TPS40210 is going to the OCP state.



    The figure-2 is shown for 5Vin to 52Vout/Iout 0.15A nonsynchronous boost regulator, and they selected the RISNS(R577)=0.025 Ohm, but the output current need to load up to 6A, the TPS40210 is going to the OCP state.



    They would like to know why they followed the equation 50 to select the RISNS=0.025 Ohm, the OCP point is 6A?

    They would like to know they select the RISNS limitation is given by equation 49 or equation 50 or other equations by you recommend?

  • 0 in reply to Henry Wang3
    TI__Guru 65550 points

    Hello Henry,

    Formulas 49 and 50 define the maximum sense resistor. Please be aware that in a boost converter the inductor current is higher than the output current. You need to calculate the peak inductor current before you can use formulas 49 and 50. 120 ohm is for sure too high.

  • 0 in reply to Brigitte
    TI__Guru 65550 points

    Hello Henry,

    As I did not hear back from you, I expect your problem is solved, so I will close this thread. If you have further questions, please either post here or start a new thread if this one is already locked.