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Parallel 2 UCC28880 Buck Converters

78Sys
Expert 1540 points
Other Parts Discussed in Thread: UCC28880, UCC28881

Can I parallel 2 UCC28880 buck converters?

I want to increase current to about 150mA, so looking at paralleling 2 UCC28880 buck converters, probably by diode ORing after the L1 inductors.

Any known issues with this?

Thanks.

  • 0
    TI__Mastermind 34465 points
    Unfortunately it is not possible to do this.
    There is a current limit section on the Drain pin of the UCC28880 and if you wire the parts in an OR configuration,
    there will be no proper current sharing between parts.
    Have you evaluated the UCC28881 ?
    This has a higher current capability.
    Regards,
    John Griffin
  • 0
    TI__Mastermind 31580 points
    Hi

    The two power stages will not share the current equally. Due to tolerance differences between the two IC's the output voltages will be different and the one with the highest output voltage will deliver all the output current until it starts to hit current limit.

    You could look up droop current sharing method which involves adding a series resistor in the output of each power supply such that the output voltage drops as the load current increases.

    The series resistors will add some power dissipation to the design.

    Regards

    Peter
  • 0 in reply to John Griffin1
    Expert 1540 points

    The UCC28881 would be great, but not yet available -- only on preview.

  • 0 in reply to John Griffin1
    Expert 1540 points
    The only readily-available IC I can find (with built-in switch) is the ST Microelectronics Viper16.