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LM5157EVM-SEPIC: LM5157

Keyrollos AbdelMasih
Prodigy 20 points
Part Number: LM5157EVM-SEPIC
Other Parts Discussed in Thread: LM5158, LM5155

Hello,

I was hoping to get some assistance for the LM5157EVM-SEPIC. Currently, I have it set such that it operates within a 10-20V threshold by manipulating the threshold resistor divider network. In addition, I have the feedback network configured so that 35V is the output and the compensation loop network is configured with a Ccomp of 4.7pF, Rcomp of 12k ohms, and Ccomp2 of 100pF. The inductor chosen is the DRQ74-150-R and the diode is the v3pm6-m3/h. Switching frequency has also been chosen to be 800kHZ. I've discovered that under no load, the module is ok and can output 35V. However, when connected to a load of anything less than 300 ohms, there is a significant voltage drop and the output is too unstable to support the load. I've tried a different combination of switching frequencies and compensation loop networks but to no avail. Guidance would be appreciated. Thank you.

Regards,

Keyro AbdeMasih

  • 0
    TI__Genius 13955 points

    Hi Keyrollos,

    Before we go deep into the details, it can be found the worst case voltage stress is more than 20V+35V. This is more than 50V absolute maximum voltage of SW pin.

    You may need to consider LM5158 or LM5155 if possible.

    Best Regards,

    Feng