Hi,
Our Analog front end is very sensitive to noise on some supplies. What is the best combination of caps given the 1500uF max and with only one Polymer cap allowed and could use some advice on how to interpret this requirement. We in general don’t have high requirements to transient behavior as the load is rather steady, but are concerned with dampening the switching harmonics.
Hi ajayt,
The single non-ceramic capacitor requirement helps with noise reduction. In fact, opting for ceramic capacitors only (no polymer capacitor) will help you reduce noise even further. This is due to ceramic capacitors having the lowest propensity for noise caused by parasitics.
When it comes to choosing the best capacitor combination, the following guidelines may provide assistance in reducing noise:
1) Ramp your capacitor values up and back down as you move away from the inductor and towards the load. (e.g. inductor, 1.0uF, 2.2uF, 4.7uF, 10uF, 22uF, 47uF, 100uF, 47uF, 22uF, 10uF, 4.7uF, 2.2uF, 1.0uF, load). Try out different combinations of ceramic capacitor values to help you achieve your goal.
2) Lay out your capacitors as pictured below - with VOUT in the middle and GND along the outside.
Please let me know if you have any further questions.
Britton
DC/DC Power Applications Engineer
