MPQ2908A Max. load current

DC-DC Power Converters
1

Hi all.

What is the maximum Iout current supported by the MPQ2908A IC?
I need to confirm whether I only need to consider the load (current) applied to the external MOSFET when applying it to an actual design, or whether I should also consider the load applied to the IC itself.

Intended load: 48Vin, Vout 12V @ 20A = 240Watt

The application note states that load sharing was used. Is it absolutely necessary to use the same configuration?

Thank you.

2

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Here are the IC characteristics showing the efficiency and case temps. It looks like the efficiency would drop off around 10A. Under typical applications under the given efficiency and temp factors, the peak typical current here is 10A.

Of course, this entirely depends on the 20A FETs that you would have and therefore your heat management solution in practice. Have you tested this?

3

The client hasn’t yet manufactured the B/D.
We’ll begin schematic work around February and begin B/D production in early March.

So, would it be beneficial from a thermal optimization perspective to use parallel FET connections instead of load-sharing two ICs?

Thank you.

4

In both of these situations, both of these methods are not bad and have their own considerations.

  • I would say it is crucial to ensure the Current Sharing of either IC or FET is balanced to prevent any thermal runaway (among many other things) and to ensure reliable operation of the system.
  • For the parallel FET case, an important factor to consider here would be the Thermal Resistance from the FET junction pin to the base. This will dictate how well the two FETs will share heat. This resistance has variables of influence like the airflow, layout design, and the placement of components.
  • Ensuring that the Thermal Coupling between devices (in either scenario) can be done with some heatsink. You can also use a copper plane ensuring the gate drive circuitry can drive a higher capacitance compared to the two load sharing ICs without overheating.

I would encourage that you test both of these methods with your client before working on the schematic to see what works best for your application.

5

Since this part is capable of driving two N-Channel FETs, the intuitive place to start would be to test two FETs that can each drive a little over 10A to start in accordance with the MPQ2908 Reference Design you had mentioned earlier.

Best,

Krishan