switch mode power supply - Techniques for Filtering a Noisy Buck Converter

I have built a buck converter on the TS30011. Unfortunately, I am getting terrible noise on the output.

External Parts Used:

Inductor

Output Capacitors

I have been analyzing my design and have been getting awful results.

My low-frequency noise is not terrible, but I am being plagued by the high-frequency noise. I have noticed two immediate errors with my design.

1) I did not separate the analog ground and the power ground as it says in the datasheet. Apparently it is only supposed to be connected at a single point, but I did not do this.

2) I must add bypass capacitors at the input of the device as close as possible.

I am hoping that these two issues alone will make my device usable, but I am wondering if there are any other suggestions for removing high-frequency noise from a buck converter.

I saw that a capacitor multiplier circuit could be used to smooth out the signal. Is this a good way of adding additional filtering? Any other suggestions would be greatly appreciated!

Answer

Input filtering is a must. In addition to that I find it a must to use at least a full GND plane when dealing with switching regulators. Along with a full GND plane you can have much better routing for the other power connections.

Some additional things to go along with that:

1. Use every effort to keep all of the VSW connections as clustered together and as small as possible. Best is to have no vias on VSW.


2. Use a cutout under the VSW node and associated pads in the GND plane and any other power planes. This helps eliminate coupling into the power and GND planes.


3. Do not route any other signals through the VSW area on any layer. This node handles the highest ripple current at high frequency and can couple to other circuits very easily.


4. Try to design your board layout so that the switcher layout is not compromised in any way. Trying to place mounting holes and non-related connectors nearby is a compromise.