Step-down converter input and output capacitors
The input and output caps are very important .The buck convertor like many others draws current in lumps ,basicly when the switching transistor inside your chip is off no significant current is drawn and current is drawn when the switch is on .The current waveform is at the switching frequency and is in a trapizoidal shape rich in harmonics and probably will have a spike on the leading edge ! SO the input cap is selected for low ESR at the switching frequency to encourage the HF crud to flow through the cap and NOT radiate along the input cable .This is why you often see in inductor in the input power wire .Most importantly the cap must be able to handle the ripple current for your product to have a long life .Generaly its easy to substitute a ceremic SMD cap here.On the output the cap must be low enough impedence to keep ripple to an acceptable level for your load AND it must handle ripple current ,not as much as the input on your orthodox chip,AND its part of the control loop in fact its ESR effects the bode plot .If you change the output cap you must check for instability.Have you considered a higher frequency approach that has no chip that reduces switching losses that will run on ceremic caps all round ? Maybe the LF chip isnt so small due to big caps and coil .