Hello,
I was testing TPS2394 on evaluation board und have several questions about that hot swap controller.
Conditions: Vin=-24V, Cflt=4.7µF, Cramp=1µF, Rsense=4mOhm, Cload=47000µF, Rload=25Ohm, di/dt=25A/s
1.Equation 4 (page 12 in datasheet) VLSS is 134V in this case.
tss=1260 x 1µF = 1260ms (Equation 3)
Vlss=(3,18µA/(2 x 0,047 x 0,000001 x 100 x 0,004)) x 1,260s²=134V (equation 4)
That means that the load can be expected to charge completely during soft start event. If I take a shot from my scope, I see that the voltage just reach 14V after soft start period. Please see attached picture: CH1-Vin, CH2-Vout, CH4: I-Inrush power supply (-24V)
2.I want to reduce the start up time to about 400ms (equation 2 and 3).
In this case I need di/dt about 80A/s, do I need? Is there another way to reduce the start up time? With di/dt 80A/s I probably would destroy my MOSFET transistor.
Best Regards
Vitali