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LM5122EVM-2PH: Current Unbalance

JasonHe
Prodigy 60 points
Part Number: LM5122EVM-2PH
Other Parts Discussed in Thread: LM5122

Hello Guys,

i have two question about LM5122-2PH DEMO board,on this components, i do not find any active current balance function for the 2 phase output, why i ask this question is because i find the the 2 phase boost inductor share unbalance current(one phase 3A, other one 5A), any methods to improve this problem?

other question is i have found that different IC(peak current control model) has different slope compensation topology, some implement the slope compensation on the Isense Pin, meanwhile other implement on the Error amplifier Output Pin, Do both methods have the same effect, what are the respective advantages and disadvantages?

Thanks!

 

  • 0
    TI__Guru 68495 points
    The LM5122 is peak current mode controlled. In 2PH demo board, one is master and one is slave, and the salve's peak current follows the masters. However, since the difference in the inductors of the two phases, and the current sense resistors variations, the sharing will be slightly different. 3A vs 5A sounds excessive. Could you measure the inductor currents and take the pictures for us to review?

    Regarding your slope compensation question, they are basically equivalent.
  • 0 in reply to Youhao Xi
    Prodigy 60 points

    Hello Youhao,

    Thanks for your explanation,So what is the TI limit Spec of Current Unbalance through both phases? 

  • 0 in reply to JasonHe
    TI__Mastermind 21720 points

    Hi Jason,

    There is no official specification as these are two different IC's (master and slave). There will be some differences similar to those Youhao mentioned, which can cause the imbalances you are experiencing. 

    Thanks,

    Garrett