MP4575 - Two ICs in parallel mode to double the Iout

Hi, we need a converter from 24 V to 12 V @ 10 A, currently we already use the MP4575, and to facilitate our logistics, we thought of putting two sources in parallel.
Is this configuration possible?
Thank you very much.

Hi Jose, welcome to the forum!

To parallel 2 outputs, the outputs must be out of phase 180 degrees (for N phases, there must be 360/N degrees of separation). The MP4575 does not accomplish this.

I would suggest instead taking a look at the MP38876, link here.

Hi Kareem, thank you very much for your prompt answer. The MP38876 has only 28 Vmax, we will use in a automotive conversor 24 to 12 V (can reach 29,4 V). This way I think to use a dual diode MBR30100 to connect the two outputs to increase the current, what do you fell ?

Hi Jose,

Is it possible to use a TVS clamp diode to absorb the input voltage peaks and keep the input to 28V? It would only have to absorb a couple volts, so it may be viable to use a small one.

Using an Or-ing configuration on the outputs will not work to double the current since they are not interphased with a common controller.

Another option is if the load currents can be split amongst various loads, you may be able to get away with having 2 separate 12V rails, each rated for 5A.

Hello Jose,

I can suggest you to look at the MP4436A (or MPQ4436A for industrial version and MPQ4436A-AEC1 for the automotive version).
You can easily use 2 of them in an interleaved 2-phase configuration, as you can see in the datasheet on pages 30 and 35 to reach 10A capability.
I believe it is our best solution for a 24V->12V / 10A application in automotive.

Best regards,
Nicolas.

Hi Kareem,
TVS clamp diode, only possible using a series resistor. When high currents are required, it is not possible to use this resistor. A TVS connected in parallel with the power line does not support the “Load-Dump” pulse, which is very powerful.
OK, I understand that it is not possible to use two or more circuits directly in parallel to increase the current, but if we use a diode in series with each output of each circuit, to make the mixing, is this possible?
The charge is only one, we cannot separate it into two or more branches.

Hi Nicolas,
Thank you very much for your suggestions.
The MP44436A has a maximum supply of + 50V, we need + 60V due to the “load-dump” pulse.
Do you have an applications notes of this IC in 24V automotive battery ?
Another solution would be: MPS have any circuit that I can use external fets and implement easily a DC-DC converte 24V to 12V @ 20 A ?

Hi Jose,
If you cannot clamp and filter Vin to limit it below 50V during load dump, then you are right that you cannot use MPQ4436A for your application.
So you should look at the MP2908A controller with external Mosfets (exists also in industrial MPQ2908A and automotive MPQ2908A-AEC1 grades). It may be possible to do 24V -> 12V / 20A with a single phase, probably with parallel Mosfets and a very large, very low dcr inductor. But I would rather recommend using 2 controllers in a 2-phase configuration (the MP2908A has a SYNCO pin, so connect the SYNCO pin of one to the SYNC pin of the other one; and short together the two FB pins; as well as the two COMP pin - to equalize as much as possible the current sharing between the 2 phases).
Best regards,
Nicolas.

Jose,
You can take a look at this reference design using MPQ2908A for a 48V -> 12V / 12A application, and adapt it to your case.
Best regards,
Nicolas.

Hi Nicolas, about the MP2908A, to use in a dual-channel operation we need connect SYNCO pin of the one to the SYNC pin of the another IC, ok, but we need to use the ENABLE function, to reduce the current when the set is not in use.
How we can to do that if the ENABLE and SYNC are the same pin ?
Do you have any aplication note using dual-channel ?
Tks again !

Hello Jose,
The easiest is to connect SYNCO of the master to the EN/SYNC pin of the slave with a series resistor. Then you can have a small transistor between the EN/SYNC pin of the slave and GND, and control this transistor with your inverted EN signal: when the signal is High the transistor is On and the EN pin is shorted to GND, so the slave stops.
There is no app note for dual-phase, although it has been tested. The MP2908A does not have any mechanism to ensure perfect current balance between the 2 phases, so it is very important to short the COMP pins together (and use only one compensation network). It is not mandatory to short the FB pins together (especially if it implies a long high-impedance trace between the 2 FB pins), but the COMP pins must be shorted together.
Note that for 20A it should be possible to do it with one single phase as well thanks to the very low Rdson FETs (by connecting 2 Mosfets in parallel for even lower Rdson) and low DCR inductors we can find nowadays (at least it can be tested).
Nicolas.

Dear Nicolas, thank you very much for your attention and explanation. We will make the connections according to your explanation. We will use a FET with low Rdson (IRFB4410) and we also thinked about using two pairs of transistors with a single IC to reach 20 A, but the price of high current inductors is very high. Anyway, if possible, we would like to send you an electrical schematic for your evaluation, is it possible ? How to send exclusively to you ?

Hello Jose, you can email me directly at nicolas.cyr@monolithicpower.com