Author Topic: Can you put diodes in parallel if they are in the same IC?  (Read 1080 times)

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Offline DmeadsTopic starter

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Can you put diodes in parallel if they are in the same IC?
« on: November 20, 2019, 04:13:48 am »
okay, I know you cant really put diodes in parallel becuase it really doesnt split current equally, but if the diodes are in the same IC, (on the same silicon die), could you then put them in parallel because they are better matched in terms of parameters?

I am thinking of doing it with this component https://www.st.com/resource/en/datasheet/stps60sm200c.pdf

the pinout/shchematic are on the first page of the link above.

Thanks.
 

Offline Hiemal

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Re: Can you put diodes in parallel if they are in the same IC?
« Reply #1 on: November 20, 2019, 05:00:18 am »
It's common practice to do that actually. If you check most AC-DC or even DC-DC converters they'll have a schottky rectifier on the output with both diodes tied together in parallel just like you're suggesting.

Since they're in the same package they also share the same rough temperature, so i can't see why it would be problematic.
 
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Offline David Hess

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Re: Can you put diodes in parallel if they are in the same IC?
« Reply #2 on: November 23, 2019, 01:49:46 pm »
Integrated diodes are not only well matched but also very well thermally coupled so they work fine in parallel.  If you were to take discrete diodes, match them, and thermally couple them, then they would also work well in parallel although not as well as integrated diodes.

For a dual power diode of uncertain construction and matching, I would not assume that placing both diodes in parallel doubles the current rating.  I might derate the parallel current rating to 75% in the worst case but in a good design, this would already be accounted for with the general derating.

In a production design, I would do some testing to find out how well the dual diodes are matched and thermally coupled if I was operating at close to their maximum limits.  Unfortunately manufacturers do not specify or discuss this that I have seen.
 
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Offline SeanB

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Re: Can you put diodes in parallel if they are in the same IC?
« Reply #3 on: November 23, 2019, 03:56:38 pm »
Those diodes are not on the same piece od silicon, but generally do come from the same die, and are relatively close to each other during manufacture, so are going to be reasonably well matched. However I would, as said above, derate them for parallel operation, and would rather regard parallel operation as a way to drop forward slope resistance and thus forward voltage drop under load, and run the pair at the same forward current as a single diode inside. Makes them easier to heatsink, as you have a lower heat dissipation from them. Drops the power dissipation from around 20W to around 12W using the 2 in parallel, making your thermal design easier. If you do need 60A choose a different dual diode rated for 60A per section instead, though you might be able to get away using 2 of the packages in parallel, making sure to match the trace lengths of the PCB to get the diodes to share current, using the PCB resistance as a rather poor but free ballast resistor.
 
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