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UCC28070: current share test

shuang qiu
Prodigy 190 points
Part Number: UCC28070

Hi,

Please advise how to test current share function of UCC28070. usually we can inject voltage to current share pin to see output voltage changes. is there pin can be used to test current share function and how to test?

  • 0
    TI__Mastermind 34465 points
    Hello shuang qui,
    You can measure the current sharing accuracy of a design that uses the UCC28070 by placing a current probe on each of the boost inductors and looking at the current waveforms on a scope. Or you can run your design at various power levels up to full power and line voltages from VMIN to VMAX and measure the temperature of each interleaved section. If one section is running hotter than the other then this is an indication of poor current sharing.
    Regards
    John
  • 0 in reply to John Griffin1
    Prodigy 190 points
    Hi John,

    Thanks for promptly reply. It's difficult to measure boost inductor current due to UUT limitation. Please advise any pin can show current value?
    As our UUT uses single UCC28070 contorol, and expect could work as multi-phase wihle some UUTs in paralleled. Is it possible to simulate current share function on single UCC28070 UUT?
  • 0 in reply to shuang qiu
    TI__Mastermind 34465 points

    Hi shuang qui,

    You can look at the CAOA and CAOB pins.
    These are the outputs of the current amplifier for phase A and phase B and they should have the same peak values and be 180 degs out of phase.

    Hope this helps

    Regards

    John

  • 0 in reply to John Griffin1
    Prodigy 190 points
    Hi John,

    How achieve current share between UCC28070s? I just saw IMO pin is shorted together on multi-phase applicaiton that is the only pin current related, is it used for current share?
  • 0 in reply to shuang qiu
    TI__Mastermind 34465 points
    Hi Hi shuang qui,
    If you want to current share between multiple UCC28070 then you need a master clock that drives the SYNC/RDM input of the UCC28070 as shown in Figure 18 of the data sheet. The IMO pin is the reference signal for the current loop. You need to short together all the IMO pins but you also need the master synchronized clock so that the phases are all interleaved.
    Without this clock then one module will drift high, supply more current and the other module will tend to supply less current.
    This is the only way to guarantee current sharing between modules.
    Regards
    John
  • 0 in reply to John Griffin1
    Prodigy 190 points
    Hi John,

    We have the external sync clock at multiphase applciation. Per figure 18 shows, VAO, VSENSE, VINAC pin shorted together also, please advise if use same parameters settings(same divider, caps) for each VAO, VSENSE, VINAC pins of different UCC28070 in multiphase, is it possible not shorted them together? any effect?
    For IMO pin, can it be used to test current share function, such as inject voltage on IMO pin to see boost output voltage?
  • 0 in reply to shuang qiu
    TI__Mastermind 34465 points
    Hi shuang qui,
    Please use the calculator tool and the application shown in Figure 18
    Otherwise your application will not share current accurately.
    IMO pin cannot be used as you describe.

    Regards
    John
  • 0 in reply to John Griffin1
    TI__Mastermind 34465 points
    Hi shuang qui,
    Since it has been over 3 weeks since your last posting I will close out this issue.
    If you have further queries please open a new posting.
    Regards
    John