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I am currently designing a circuit to drive a high power laser-module at 12V/40A. I found the idea from Marco Reps https://github.com/marcoreps/laser_driver very inspiring for my design. Since the power to drive the laser is so high I decided to utilize 2 Converters instead of 1 module to save costs because DC/DC - Converters at 500W are kind of expensive. I found the I6A4W02033V from TDK which can supply 20A at 3,3V to 15V. These converters already have a sync option so I think it should be possible to parallel them. The Datasheet states https://product.tdk.com/info/en/documents/spec/dc-dc-converter/i6a4w_spec.pdf that one converter can be configured as master by connecting its MS pin to VIN and connecting SYNC from the master to the SYNC from the slave device. It also says that the SYNC signal from the master can be inverted by connecting it to GND instead of VIN. I had the idea to invert the signal to reduce noise on the combined outputs since in my theory the ripple voltages of the converters should theoretically cancel each other out as they are phase-shifted by 180°. Is this approach possible to reduce noise or do I miss something there?

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  • \$\begingroup\$ If I remember well here is a specific IC from LTC that can generate those SYNC signals for interleaving. LTC6902 \$\endgroup\$ – Marko Buršič Jan 17 at 13:07
  • \$\begingroup\$ Look at this bargain: Murata UCQ-1.2/30-D48NHL2-Y : aliexpress.com/i/… \$\endgroup\$ – Marko Buršič Jan 25 at 16:11
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You're right about driving different converters (power trains) with different phases of a master sync clock. Doing so increases the ripply frequency on the output and thus makes it easier to filter. We design/build SMPSs with multiple power trains (2 & 4 being the most common) all the time.

But in your case, you need to make sure the individual converters allow themselves to be connected in parallel. If they do, it should be so stated on the data sheet. If not, you run the risk of one converter trying to supply all of the load current. I skimmed through the data sheet for the converter you referenced and did not see any discussion about operating converters in parallel.

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I'm unsure that they can be connected in parallel and, for me, the only realistic option is to build one yourself using the LTC7871 (for instance): -

enter image description here

The picture above shows a 24 volt output capable of delivering 180 amps so, re-arranging a couple of values to give 12 volts out isn't going to be a hardship. If you dig through the data sheet details you'll probably find that when operating with 12 volt on the output, the input voltage can be significantly lower than 36 volts too (if that helps).

You can also buy a demo board too: -

enter image description here

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  • \$\begingroup\$ Thank you for your suggestion! Although the input voltage isn´t that big of an issue this circuit would probably make the voltage regulation a bit easier and get rid of the issues of load sharing but I am not sure whether it can achieve the low ripple needed for sensitive laser-diodes. However I will definitely look into the datasheet a bit further. \$\endgroup\$ – Leonard Reber Jan 17 at 13:21
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I do think that, if you wan't to use just two devices in interleving mode with 180 degrees, the module already support this without any other needs.

Synchronization:

The i6A modules can be synchronized to one another or to an external clock within ±20% of nominal value shown on electrical characteristics page by using pin 32 (SYNC) and pin 33 (MS). Interleaving of switching can also be achieved for input noise cancellation.

If MS pin is tied to Vin pin it will become a clock master. In this mode pin 32 (SYNC) will become a clock output that can be used to synchronize other i6A power modules.

If MS pin is left open, then pin 32 (SYNC) will become a clock input and the module will synchronize to the clock signal with no phase shift.

If MS pin is tied to GND then pin 32 (SYNC) will become a clock input and the module will synchronize to the clock signal with 180-degree phase shift.

In bold you have the combination 1st master, SYNC becomes the output for 2nd slave, SYNC input with 180 degrees shift.

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