Friday, 20 June 2014

Ceramic or electrolytic capacitors for a switching buck regulator?


I'm using the LM2734Z (step-down DC/DC converter), which operates at 3 MHz. I'm using it to step down 4.8 V - 20 V down to 3.3 V +/-5%. Is it better to use ceramic capacitors or electrolytic capacitors in this circuit?



They seem to show ceramic capacitors in the datasheet, but would electrolytic capacitors be smaller and better at filtering ripple and handling load transients? Size is critical for this product, and cost is a minor issue. I would like the operational temperature range to be -40 °C to +85 °C, if not that then -20 °C to +70 °C.



Answer



With chips like that it's best to follow the manufacturer's design closely, unless you really know what you are doing. Ceramics are generally preferred in that sort of application, they are smaller and more reliable than electrolytics, handle high temperatures better, and often have a lower ESR.


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