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LM5122: General Review, Additional Diode, and Current Limit

Thomas Westrick
Prodigy 20 points
Part Number: LM5122

I have a schematic for an LM5122 boost 20V-33V input; 36V, 4.5A output for PDS-2638 that I had some questions on.

Using the power stage designer, the peak inductor current is 9.37A (at the min input voltage). Using two 12mohms in parallel as a sense resistor, there is a 12.5A current limit. But at the maximum value of the current limit threshold of 87.5mV, the current limit is 14.6A which saturates the inductor. Is this something to worry about (in case of current spikes) or is that maximum spec not likely?

Also, is the 'Additional Parallel Schottky Diode' I have in the schematic a good selection?

If you have any other suggestions for the schematic, please let me know.

Thank you for your help,

Thomas

  • +1
    TI__Intellectual 2775 points

    Hi 


    Inductor saturation is a very dangerous thing. It is recommended to choose an inductor with a larger saturation current.

    You can parallel a Diode. However, the current capability and loss of the diode need to be considered.

    about the SCH:

    1)advise add a 0.47uf cap for Pin5(Vin)

    2)advise add a 100pf cap for Pin6(UVLO)

    3)advise add a 4.7uF cap for Pin17(Vcc)