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LM5088-Q1: Unsolvable Mystery

GOVINDARAJ KRISHNAN
Prodigy 130 points
Part Number: LM5088-Q1
Other Parts Discussed in Thread: LM5088, CSD19534Q5A

We are testing LM 5088 based buck converter,

Input voltage: 48V

Output: 12V

Output current 5A

Switching frequency: 500Khz

Diode Part number: Digikey V40PW10C-M3/IGICT-ND

Mosfet Part number: Digikey 497-15305-1-ND

Problem:

1) Enable pin ringing

2) Output ringing

3) Can't able to load more than 2 A

Please suggest the way to move forward.

  • 0
    TI__Guru 74422 points

    Hello,

    I recommend changing the MOSFET as it has a very high gate voltage Miller plateau of 6.2V (see STD105N10F7AG datasheet, Figure 8). This means that very little overdrive is available given the LM5088's gate drive amplitude corresponding to the VCC of 7.8V minus the boot diode drop. Try using the CSD19534Q5A 100V NexFET (super low Rdson is not required as the duty cycle is only 25%).

    Also, I recommend filling out the LM5088 quickstart calculator file for this design to check component selection. In particular, note the ESR of the 180uF output cap.

    http://www.ti.com/product/LM5088/toolssoftware#devtools

    Regards,

    Tim