Why does the output ripple and load transient measurements show so much noise on my oscilloscope from my DC/DC converter? Below is my set-up and waveforms.
The conventional way of measuring signals with a probe and ground loop creates a large area for noise collecting. The loop causes parasitic inductances causing inaccurate measurements. One method to reduce these artificial noise is to use a tip and barrel method. Remove the ground wire and probe hooks. There is a metal barrel on probe which is connected to the common ground. Connect the tip of the probe to vout and lean the probe where the barrel will touch the ground node. Usually the connection point will be at the output capacitors. One way to make the method easier is to wrap metal wire around the barrel to use as a tip. This will cause a loop, but much smaller compared to the previous method.
I think:
a bead is needed at the output stage,
adding more output cap will reduce the low freq ripples
I can not see any reference design talking about frequency transition SMPS in MPS website
Hi alhuselectron,
These are great methods for reducing output ripple from a circuit standpoint. If there is still too much ripple after taking the above method to measure on the oscilloscope, then more output cap or a secondary output filter should be added.
Thanks,
Brendan