MOSFET Selection LTC4364

Bubbles27 said:

Is there a way to make the turn-on time faster?

Speeding up start-up time and increasing inrush is not the answer to blown FETs.
Once you select the inrush current and assume max Vin, check if the HGATE FET has the Safe Operating Area (SOA) performance to survive start-up.

Bubbles27 said:

Which MOSFET would you recommend if we were to replace the SQJQ184E? We are very space-constrained. Should we look at a MOSFET with smaller input capacitance?

Small Ciss isn't important in hotswap applications, since we intentionally add Cgate for inrush control.
You want FETs optimized for SOA performance.
Here's an example of such a FET: PSMN3R7-100BSE

Bubbles27 said:

• The maximum expected current through the channel is 60 A, this will only occur once the MOSFET is switched completely on.
• The maximum turn-on current is 20 A.

Make sure the load is off until Cout is charged (Inrush=0A).
Otherwise, the load current is added to the SOA stress.
Use the ENOUT pin to signal the downstream load that start-up is complete.

Thank you for the response.

• The SOA of the PSMN3R7-100BSE does not look better than the SQJQ184E
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• Ashapiro said:

  Make sure the load is off until Cout is charged (Inrush=0A).
  Otherwise, the load current is added to the SOA stress.
Yes that is what I feared. We were hoping to save on having to protect an output to a DAL-B device which we expect not to fail but having the possibility that it short circuits causes this problem.
• Ashapiro said:

  Use the ENOUT pin to signal the downstream load that start-up is complete.
Yes, we will reconsider our power architecture.

Regarding the SOA graphs, I'll refer you to this article about the Spirito Effect from the great Dan Eddleman.
https://www.analog.com/en/resources/technical-articles/mosfet-safe-operating-area-and-hot-swap-circuits.html

I'm skeptical because the SQJQ184E-T1_GE3 SOA curves are perfectly straight and in parallel.
There's no Spirito region, so I wouldn't trust its advertised SOA performance.

Thank you Ashapiro, this is really helpful. I will look into this article. Which MOSFET manufacturer would you say is trustworthy?

Thank you Ashapiro, this is really helpful. I will look into this article. Which MOSFET manufacturer would you say is trustworthy?

Nexperia
Alpha & Omega Semiconductor