I use 1% resistor all the time... cheap... nothing special... I will send more info later this weekend when I can looks at my notes... with surface mount resisters and diodes, you can mount them on the back of the board to save room.......
On Sat, Nov 1, 2014 at 2:35 PM, John Monahan <[email protected]> wrote: > Ok Tom, I’ll take your suggestion. I’ll overlay them in the space as for > the 78H05. That way at least for the 5V CPU’s one could use either option. > > > > Since you have used these regulators. Could you give me the exact specs > (possible part numbers) for the diodes & inductors. > > I’m a bit worried with the adjustable to get to 3.3V. Always worry that > somehow the resistors will go out or range and give an over voltage. Are > the resistors special, 1% etc. > > What wattage. > > > > > > *From:* [email protected] [mailto:[email protected]] *On > Behalf Of *Tom Lafleur > *Sent:* Saturday, November 1, 2014 1:04 PM > *To:* [email protected] > *Subject:* Re: [N8VEM-S100:5497] 80386 CPU Board - Component type/value > clarification > > > > the chips are small and so are the parts... so use TWO of them.... > > also, I always add room for the two trim resisters just in case I want to > change the output voltage a bit... > > > > On Sat, Nov 1, 2014 at 11:59 AM, John Monahan <[email protected]> > wrote: > > Good point Tom, will switch! > > In an ideal world I would like to have 5V at say 3-5Amps out, but also 1 > -2 Amps at 3.3V for a AMD 5x86 (the Pentium like CPU) Tom mentioned > earlier today. Has anybody see a dual output chip – just asking! > > > > John > > > > > > *From:* [email protected] [mailto:[email protected]] *On > Behalf Of *Tom Lafleur > *Sent:* Saturday, November 1, 2014 11:39 AM > *To:* [email protected] > *Subject:* Re: [N8VEM-S100:5492] 80386 CPU Board - Component type/value > clarification > > > > John... > > > > A much better switcher is the LM22677/78, its rated at 5amp, has a very > low 100 mOhms output switch (lower heat) and operate at 500Khz or 1Mhz > allowing for a much smaller inductor and output C... TI has a number of > variants of this part.... The TO263 case is easy to use, I just put a pair > of small 4/40 holes under the power pad and solder it from the back side on > my prototypes... I use a Bourns inductors and low cost Panasonic output C.. > there all surfaces mount, but they are large and very easy to solder... > same with the diode... Other part can all be size 1210 or larger parts, > again easy to solder... even with my older eyes... > > If you need 2-4 amp or so, this is the part I use in my designs and I > would recommend... > > > > There are many other parts like this, but this one is easy to get, simple > to use ect.... > > > > The LM2576 is rated at 3amp, and switched at 50Khz, requires a very large > inductor and very large output C.... > > tom lafleur > > > > > On Fri, Oct 31, 2014 at 3:04 PM, John Monahan <[email protected]> > wrote: > > I think I did 4 prototypes on this board Dave, Played around a bit with > the caps early on. Did not seem to make a difference (at these low > frequencies). The Intel manual has a whole section on board layout. See > one page attached here. I ended up with 0.1’s and two 1uF Tants on C71 & > C54. Probably more important is the actual power supply. Doing the 80486 > I’m learning a lot! On that board I’m bring special wide traces directly to > the chip. Also if you can get your hands on one, get a 74H05. There are so > many of the 3Amp regulators that are out of specs, it’s ridiculous. While > I have a board running at 4.8V’s with one, I really don’t like it. > > > > I am also looking into these newer LM2576’s. See attached. Know anything > about them. > > > > BTW, I’m also doing a direct SMD 32MB RAM daughter board (like our 16MB > board). Again a tight board fit (see an non optimized version). I will > order 4 for myself but since its completely untested I’m not going to > announce it yet. But just FYI. > > > > Let me know how the 80386 works. The only thing I’m not comfortable with > on that board is the “kludge” to stretch out the pWR* signal. I hope to do > it better (clock independent) on this 80486. > > > > John > > > > > > > > *From:* [email protected] [mailto:[email protected]] *On > Behalf Of *David Fry > *Sent:* Friday, October 31, 2014 2:37 PM > *To:* [email protected] > *Subject:* [N8VEM-S100:5481] 80386 CPU Board - Component type/value > clarification > > > > Hi John, > > > > I am slowly starting to populate my 80386 PCB with capacitors and have a > query regarding C51 and C74 (positioned either side of the 80386 CPU). > > The schematic would suggest that these are 0.1uF multilayer ceramic > capacitors like the rest, but the pictures on most versions of your 80386 > boards would seem to indicate you have used a tantalum bead capacitor in > these two positions. > > > > Please can you clarify what type & value of capacitor should be used here. > > > > regards and thanks > > > > David Fry > > -- > You received this message because you are subscribed to the Google Groups > "N8VEM-S100" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "N8VEM-S100" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > > > > > -- > > > ~~ _/) ~~~~ _/) ~~~~ _/) ~~~~ _/) ~~ > > Tom Lafleur > > -- > You received this message because you are subscribed to the Google Groups > "N8VEM-S100" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "N8VEM-S100" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > > > > > -- > > > ~~ _/) ~~~~ _/) ~~~~ _/) ~~~~ _/) ~~ > > Tom Lafleur > > -- > You received this message because you are subscribed to the Google Groups > "N8VEM-S100" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "N8VEM-S100" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- ~~ _/) ~~~~ _/) ~~~~ _/) ~~~~ _/) ~~ Tom Lafleur -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. 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