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LM5122: Dual Phase Interleaved Boost Configuration question.

WU YISYUAN
Expert 2165 points
Part Number: LM5122

hi,

I use Dual Phase Interleaved Boost Configuration have some question.

my design parameter is : Vin=12V, Vo=30V, Io=7A(total)

1. if mode pin pulled down GND, Vo=Vin, and output is no load. I check Ho and Lo waveform, Ho no signal, and Lo waveform like below:

when I use resistance pull up mode pin, the converter is work. why can't pull down the mode PIN to ground?

2.To solve item 1, the other question is when I add output load, add to 3A, the output Vo is drop from 30V to 18V.

It not look like OCP protect. What caused it?

my circuit as below:

many thanks.

  • 0
    TI__Mastermind 21720 points
    HI WU,

    The MODE pins should simply modify the device to operate in DCM (GND) or CCM (Pulled up). Can you please check and make sure that you are making the correct connections? This might be the cause because the LO duty cycle is close to the maximum which indicates that the LM5122 is operating correctly but the LO MOSFET might not be getting turned on. Also in the future please connect the source of the low side FET to PGND and not AGND. AGND is intended to be used for noise sensitive signals.

    Thanks,

    Garrett