Hello team,
We have encountered some misalignments regarding the RTrip values when designing on Webench with the TPS53319.
For a 12V VIN, 1.03V VOUT, 500kHz FSW, 14A IOUT design, Webench recommends a 280kOhms RTrip and a 510nH inductor. If we use the formula on the datasheet for calculating IOCP (page 16), we get an IOCP of 24A, but the TPS53319 can only output 14A. If we use the formula to calculate RTrip (page 23) for 14A and using the same 510nH inductor, we get a RTrip of 149.49kOhms. Similarly, if we calculate using the same inductor and 1A IOCP we get negative resistance values, -10.40kOhms.
Now, if we modify the Webench design for the same voltage specs but a 1A IOUT, Webench recommends a 301kOhms RTrip and a 5uH inductor. Doing the same exercise of calculating IOCP with these values we get IOCP=24A . Calculating the correct RTrip value gives 169kOhms. I have attached an excel file with these calculations.
The question is: what is the correct way to calculate RTrip? Do you need to keep the inductance value fixed based on the current limit? Which is correct: Webench or datasheet?
Also, what is the maximum RTrip value for the TPS53319, I read on another post it was 300kOhms, but the datasheet doesn't make any mention of this for the TPS53319; it does mention the limit for TPS53318 which is 150kOhms.
Let me know if you have any questions. Thanks.