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TPS2490: How to get both long enough Fault Timeout and good margin of MOSFET SOA

Part Number: TPS2490
Other Parts Discussed in Thread: CSD17570Q5B



My customer is designing a hotswap circuits using TPS2490 and CSD17570Q5B.

Their requirements are as follows.

Vin=Vo=12V, Io=25.4A(max), Ta:0~+75oC

Cout=2460uF, ILIM=33A, PLIM=150W, VPROG=0.545V, Vuvlo=9.8V

Their schematics are as follows.

Using the TPS249x_8x_Design_Calculator_REV_B.xlsx calculator, to get enough SOA margin during "hot-short" or "start-into short" at F91, my customer needed to select Ct=0.47uF. Then the Fault Timeout becomes 0.075ms. However, according to equation (17) and (18) in the datasheet, calculated tstart is ~1ms or ~1.8ms, this is larger than 0.075ms. So, the Fault Timeout always prevent correct start-up.

Please let my customer know how to fix this issue. (Please refer to the attached TPS249x_8x_Design_Calculator_REV_B 2020 2 16.xlsx)

TPS249x_8x_Design_Calculator_REV_B 2020 8 28.xlsx

Best regards,