LMR14050: LMR14050 input ripple ring solution

Hi Yan

There are two ways to reduces this ringing.

1. Place small value cap (1nF) close to Vin pin and try to minimize its GND return path as much as possible.
2. Increase value of R13 to slow down the SW node. I see its already quite high. Increasing further might impact efficiency.
3. Increase the value of snubber cap

Thank you

Regards

Onkar Bhakare

1. Place small value cap (1nF) close to Vin pin and try to minimize its GND return path as much as possible.-----Why 1nf?

3. Increase the value of snubber cap-----if  I increase the value of snubber cap,whether the snubber resistor will exceed its power limit?

Thank you

Regards

yan

Hi Yan

1. Small caps (1nF, 0.1uF) connected in schematics will have lower Series Resonant Frequency (SRF) thus will be able to suppress high frequency spike more effectively than higher value cap. It's a good practice to keep capacitor closer to IC in ascending order.
2. Yes, with higher snubber cap you would need resistance with higher power rating

Thank you

Regards

Onkar Bhakare

What is the cause of this 33.33M oscillation？

Thank you

Regards

yan

Hi Yan

This result of ringing due to practice inductance of Vin - SW trace and internal bond wires with input capacitor. Thus, in order to damp this following step could be used as specified earlier

1. Place small value cap (1nF) close to Vin pin and try to minimize its GND return path as much as possible.
2. Increase value of R13 to slow down the SW node. I see its already quite high. Increasing further might impact efficiency.
3. Increase the value of snubber cap

Thank you

Regards

Onkar Bhakare

Hi Yan

Let me know if any further questions

Thank you 

Regards

Onkar Bhakare