LM5069: LM5069 - Gate series resistor of parallel mosfet application

Hi Aska,

Thanks for reaching out!

Can you please fill the LM5069 design calculator and send us for review. The design calculator is available under the product folder at ti.com

Yes, we have to use parallel FETs to support higher current by connecting the GATE through a series resistor of 4.7Ohm for each MOSFET.

Best Regards, Rakesh

Dear Rakesh:

Appreciated your reply.

So far the series resistor is 3ohm on my circuit.

In fact, I doesn't understand the calculator in detail. But I tried to fill up it.

Could you please check whether there is any problem?

Thanks.

AskaLM5069_Design_Calculator_REV_C.zip

Hi Aska,

The design fails to meet SOA margin with the selected FET. You need to use stronger SOA MOSFET like PSMN4R8-100BSE. Please modify the design with PSMN4R8-100BSE parameters and send to me for review.

Can you please share the use case of this circuit in your system? Do you need 48V/100A protection solution ?

Best Regards, Rakesh

Dear Rakesh:

Appreciated your reply quickly.

Follow your suggestion, I just got the samples (PSMN4R8-100BSE) today.

Because the input voltage is variable from 48V to 30V, the input current shall be 70A to 100A max. But it is only 6~7 minutes run time (from min current to max current).

So the run time of 100A shall be 10 ~ 20 seconds.

Could you please help to review the file before I test new mosfet? 

Thank you so much.

Aska6114.LM5069_Design_Calculator_REV_C.zip

Hi Aska,

Understood.

But 10-20 seconds is still to be considered as DC for FET.

Please use the parameters as per the attached design sheet.

2117.LM5069_Design_Calculator_REV_C.xlsx

Best Regards, Rakesh