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Building Tiny DDL Driver

Wolfman29

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Ah, alright, that makes sense. So what type of cap would you recommend for the input/output caps? I ordered 50 uF SMD caps from Mouser, I figured I would use those. Are those alright?
 





jib77

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Wolfman29 said:
Ah, alright, that makes sense. So what type of cap would you recommend for the input/output caps? I ordered 50 uF SMD caps from Mouser, I figured I would use those. Are those alright?
Click to expand...

Ceramic caps are recommended as they have very low ESR ratings. Please post the link to the ones you got from mouser and Ill check them out.
 
rhd

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Jib:
Thanks for the clarification - very much appreciated.
(Is it ok to address you as "Jib"? Lol, "Jib77" sounds so formal!)

I haven't been protecting the inputs of my LM1117 drivers with caps, just the outputs - so I need to correct that in future builds. I've been using a 10uF electrolytic radial cap for the output to diode. But truthfully, I don't really know if I should be using 1uF, 10uF, or 100uF. And does it need to be ceramic for the diode cap too? Or is it just the LDO IC that cares about low ESR?
 
Wolfman29

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Perfect! I can't wait to begin building my driver... I guess I will make a new thread for it once it's fully built with pictures and parts and stuff! Should be fun. Now I just have to wait until Saturday or next Monday to get my parts (I assume, because it is shipping within the US).
 
jib77

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rhd said:
Would you suggest 10uF for both input to driver and output to diode?
And since I'm a sucker for the low shipping costs on eBay, could I get away with:
Fujicon Electrolytic Cap 10uF 50V 105C LOW ESR x25pcs - eBay (item 320657250404 end time Mar-15-11 23:00:51 PDT)

?
Click to expand...

I cant find their ESR rating anywhere, "LOW" in this case is a marketing term used to say its lower than the other guys, not an indication of its actual rating ... but my gut feeling is no. Only ceramic and very expensive tantalum caps have the low ESR needed. You can always parallel a small cheap ceramic (like a 0.1uF) with the electrolytic to keep the ESR down.
 
rhd

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One other question - Do we have an LDO version of the LM338?

IE - the low dropout of the LM1117, with the higher current capabilities of the LM338, and the same pinout as all of the above?
 
jib77

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LM1084 - National Semi
LT1084 - Linear Tech
LD1084 - ST Micro
 
jib77

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Yup ... LM338 is a 5A part, so 1084 is the 5A LDO equivalent. But 1085 can be used too if you dont need more than 3A. All have same pinout.
 
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