LM74502EVM: 5A maximum current limitation - why?

Supira Medical

Part Number: LM74502EVM
Other Parts Discussed in Thread: LM74502H-Q1, LM74502-Q1

Hi,

The EVM has a 5A current limit using one pair of MOSFET's. The datasheet of the MOSFET shows that it has a significantly highly Id. What is the limiting factor in the EVM, is it thermal or is it a limitation of the PCB traces?

Thanks!

over 2 years ago

0 Praveen GD over 2 years ago

TI__Guru 57737 points

Hi Supria,

The EVM is capable of handling 10A load current. We have specified 5A considering some margin.

You can use it for 10A without any issue as long as the FET thermal allows for it.

0 Supira Medical over 2 years ago in reply to Praveen GD

Intellectual 300 points

Hi,

Thanks for the response. I am attempting to make a 75A switch (for 12 volts). Any recommendations on the rating of FET's I should use, assuming they will have adequate thermal management? With the 65 uA gate drive, is there a practical limit to the number of FET's one can parallel?

0 Praveen GD over 2 years ago in reply to Supira Medical

TI__Guru 57737 points

Hi Supria,

The gate drive source current of LM74502-Q1 is 60uA while LM74502H-Q1 has 11mA.

LM74502-Q1 is designed to have lower gate drive strength so that there is inrush current limit while starting up into capacitive loads.
On the other hand LM74502-Q1 is designed to have higher gate drive strength for fast turn ON of FETs where inrush current limit is not required.

Both the controllers will not have any issue in driving parallel FETs to carry 75A load current. You can choose the H or non-H controller based on your requirement.

0 Supira Medical over 2 years ago in reply to Praveen GD

Intellectual 300 points

Hi Praveen,

Many thanks! One final question for you - is there really any difference between the automotive and non-automotive versions other than certification? It looks like the only ones available at the moment are the non-automotive ones.

0 Praveen GD over 2 years ago in reply to Supira Medical

TI__Guru 57737 points

Hi Supira,

The performance of the automotive and non-automotive versions of the IC would be same. As you mentioned only the Automotive qualification/rating is the difference.

0 Supira Medical over 2 years ago in reply to Praveen GD

Intellectual 300 points

Thanks so much for all the help!

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LM74502EVM: 5A maximum current limitation - why?