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CSD86360Q5D: Connect two devices in parallel - allowable/advisable?

Part Number: CSD86360Q5D

Can two "CSD86360Q5DSynchronousBuck NexFET™ PowerBlock" converters be connected in parallel for increased current capability?

  • Hi Shawn,
    Thanks for your interest in TI Power Blocks. It is possible to parallel two of the power block devices. However, you probably cannot get 2x the current capability due to mismatches in the individual FETs within the power blocks and the effect it has on both dynamic and static current sharing. There will most certainly be some amount of current imbalance between the two power blocks. Luckily, due to the positive temperature coefficient of rds(on), there tends to be a thermal balance between the power blocks and of course, you're spreading the dissipation between two packages over a larger surface area. With that in mind, here are some rules to follow when paralleling power blocks:

    1. PCB layout needs to be symmetrical for all FETs, including the gate-source and drain-source loops as well as the gate drive and return paths from the driver IC or control IC.
    2. Switching speed needs to be tuned to allow all FETs to turn-on and off with about the same delay. A few ns of delay mismatch will overstress the FET and cause possible FET damage. This is best accomplished by symmetric layout and the use of individual gate resistors for all FETs.
    3. As stated above, each FET needs to be have its own external Rg (usually 1 to 3 ohms is sufficient) to prevent oscillation during switching and to swamp out any differences in the internal gate resistance of each FET.