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LM5143: LM5142 output not observed.

RAGUL S
Prodigy 20 points
Part Number: LM5143

Tool/software:

Hi,

      We designed Dual Synchronous Buck Controller using LM5143QRWGRQ1 for input voltage of 50V and output load of 5V, 30A.

When we powered ON the module at no load, with input set voltage of 50V and set input current limit of 50mA in external power supply. It results failure of IC (VCC pin short was observed) and module output voltage not observed.

However at same condition, we increased the input set current limit in external power supply of 1.5A, it works and output voltage was observed at 5V.

We connect VCCX pin of IC to output voltage 5V, to reduce the power dissipation of LM5143.

Is there any possible of failure of IC, with lower set input current limit in external power supply? Or any other reason for this failure?

  • 0
    TI__Genius 14916 points

    Hello Ragul

    Could you share your schematic? 

    Meanwhile I'll look into it and get back to you

    Thank you 

    Regards

    Onkar

  • 0 in reply to Onkar Bhakare
    Prodigy 20 points

    Hi Onkar,

    Thanks. Which pin connectivity did you want for your analysis.

  • 0 in reply to RAGUL S
    TI__Genius 14916 points

    Hello Ragul

    Input current limit of 50 mA might not be sufficient even if converter is operating at no load. Converter will take significant amount of current to charge output capacitance during startup. If current limit is lower than the inrush current requirement, it would prevent the converter from initiating its operation properly. It could lead to issues like slow startup, failure to start at all.

    Can you please confirm the value of output capacitance in your design? 

    Additionally, share your schematic, it would help in debug process.

    Moreover, if you could share some startup waveforms of following nodes that would be great!

    1. SW
    2. Vout
    3. Vcc
    4. Vin (across the closest input cap) 

    Thank you

    Regards

    Onkar Bhakare

  • 0 in reply to Onkar Bhakare
    TI__Genius 14916 points

    Hi Ragul

    I am closing the thread due to inactivity. feel free to reopen at any time

    Thank you

    Regards

    Onkar Bhakare