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LM5013-Q1: Output Voltage Error

En Dy
Prodigy 55 points
Part Number: LM5013-Q1

Tool/software:

We had built a dual 5/5.3V supply to be fed from a 22.2V-75V input, the design was verified here. https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1389988/lm5013-q1-design-feasibility-for-drone-high-voltage-power-module

On receiving three boards for testing, the first output (top) was found to be well performing but the bottom one gives us erroneous changing voltage on the output. The input voltage was kept between 18-23V. Attached are the oscilloscope waveforms.

Output voltage measured across output capacitors and output solder pads at 18V

Inductor voltage

Switch-GND voltage

The BOM is given below

Please help us understand what could have gone wrong. Thanks in advance!

Regards,

Nilabha

  • +1
    TI__Expert 5090 points

    Hi Nilabha,

    Can you please double confirm about the feedback resistor values present on the board?. Also, if you configure the first output to 5.3V, do you get proper voltage across the output? 

    Thanks,

    Nitya

  • 0 in reply to Nityanand Hegde
    Prodigy 55 points

    Hi Nitya,

    We were able to find the error, it was a PCB design issue from our side where the designer had not connected the voltage setting resistors to the output pin on the lower converter.

    A drop of solder fixed it and both converters are working fine at 5.0V, and we will move onto more detailed tests. Thanks a lot for your help!

    Regards,

    Nilabha