I am adding a buck converter SMPS IC to my PIC serial data translator/transceiver in order to be accept a source voltages of 12v or 28v DC, output 5V for IC's @about 50 to 60mA load. PIC is running on a 20mhz crystal. Attached is the schematic (The 7805 will be replaced by the SMPS).
It's my first time using a buck converter. I've read about them, done research, some shopping and now have a few questions. This device is for somebody else so i value reliability over component price. I can't have issues about brown-outs or EMI once it's shipped, obviously. I'd like to minimize footprint but that's a lower priority (but excludes ready made 20$ smps boards).
1. It seems the major hassles with buck converters are related to the inductor and pcb EMI due to traces. I've searched for "integrated inductors" to mitigate this and found that TI and Enpirion make some but they only accept input voltages up to 5.5v.
Anyone knows of integrated inductor buck converters accepting from 12v to 28v input? I might have missed them. Or are there other solutions without inductors? Preferably thru hole (haven't done SMD yet but could always solder it i suppose).
2. How much ripple can my design tolerate? Worst case is the recommended max / min IC supply voltages (taking into account the 4.35v max brownout on the pic)? Obviously i will try to minimize ripple as much as possible.
3. If i understand correctly, in designs using inductors, ripple is minimized by using low esr output caps and higher freq switching?
4. About inductor selection, is there anything i should know about or look out for when choosing for SMPS? AFAIK the specs i should care about are inductance value, max current and and physical size. I've never shopped for inductors before and maybe used one once like 20 years ago.
5. What is the effect of inductor resistance on SMPS? For my design, is this important and if so how do i evaluate the max allowable resistance?
I've shopped around and read other threads recommending specific ic's for their designs but if you know one in particular (stable, reliable) i'd appreciate the suggestion.
Thanks!
It's my first time using a buck converter. I've read about them, done research, some shopping and now have a few questions. This device is for somebody else so i value reliability over component price. I can't have issues about brown-outs or EMI once it's shipped, obviously. I'd like to minimize footprint but that's a lower priority (but excludes ready made 20$ smps boards).
1. It seems the major hassles with buck converters are related to the inductor and pcb EMI due to traces. I've searched for "integrated inductors" to mitigate this and found that TI and Enpirion make some but they only accept input voltages up to 5.5v.
Anyone knows of integrated inductor buck converters accepting from 12v to 28v input? I might have missed them. Or are there other solutions without inductors? Preferably thru hole (haven't done SMD yet but could always solder it i suppose).
2. How much ripple can my design tolerate? Worst case is the recommended max / min IC supply voltages (taking into account the 4.35v max brownout on the pic)? Obviously i will try to minimize ripple as much as possible.
3. If i understand correctly, in designs using inductors, ripple is minimized by using low esr output caps and higher freq switching?
4. About inductor selection, is there anything i should know about or look out for when choosing for SMPS? AFAIK the specs i should care about are inductance value, max current and and physical size. I've never shopped for inductors before and maybe used one once like 20 years ago.
5. What is the effect of inductor resistance on SMPS? For my design, is this important and if so how do i evaluate the max allowable resistance?
I've shopped around and read other threads recommending specific ic's for their designs but if you know one in particular (stable, reliable) i'd appreciate the suggestion.
Thanks!