I'm putting together a SMPS with the LT1074 (8-60 V in 5 A out 100 KHz with 100 uH inductor) the datasheet specifies a 500 uF output condenser but I don't have one. can i use a bigger one ? what about 1000 uF ? otherwise it will have to be 3 X 220 uF (660)
ok but I'm also thinking am i better off with one 1000 uF or 3 X 220 uF for in/out current carachteristics ESR its called I beleive or am I being over fussy for 100 KHz (this is the second only SMPS I build last one was real simple - still proud of it)
For your switching frequency ESR is more important than capacitance. It is often better to have several smaller caps in parallel than a single large one.
bearing in mind I've already doubled the inductor size from 50 uH to 100 uH (on sound recomendations) so would larger capacity be even more so appropriate ?
I've used the LT1070 LT1170 and LT1268 quite a lot. Even though they are boost and yours is buck, they seem well built and very forgiving.
3x caps in parallel would be nicer.
Also I just find a chunk of ferrite big enough to choke on and wind it full of heavy gauge wire. The inductance value I've never bothered with. You might pay attention to it if you were designing for a mass produced item, as you would need a part you can replicate.
bearing in mind I've already doubled the inductor size from 50 uH to 100 uH (on sound recomendations) so would larger capacity be even more so appropriate ?
Why did you do this? Did you also halve the switching frequency to make up for it?
Inductance is inversely proportional to switching frequency and load current, so if you increase the inductance, you're decreasing the needed switching, as well as decreasing the total output current.
I got the chip and inductor from picbits, he said the larger one would be fine and thats how he's using them, the chip will auto compensate and reduce frequency as neccesary