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I'm looking for a buck converter in a SOIC-8 package which requires a small inductor (preferably ≤10µH) which can convert 6V-16V to 5V @ 1A. Unfortunately the package must be a SOIC package, because the person I'm designing for requires the SOIC package to be easy to place and solder. At the moment I've drawn a blank: all the high speed buck converters I have found only have a 6V or so maximum input voltage or they come in strange packages which are difficult to hand solder.

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    \$\begingroup\$ Why SOIC8? What about other easy to solder packages? Simple switchers are monsters but can be soldered with your eyes closed. Part of your problem is not many vendors are making high switching frequency chips in SOIC8. \$\endgroup\$ – Chris Gammell Oct 29 '10 at 11:26
  • \$\begingroup\$ I'm designing it for someone who only wants to solder 1206 packages (because 0603 and 0805 are too small), I imagine that anything smaller will be tricky for them. \$\endgroup\$ – Thomas O Oct 29 '10 at 11:29
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    \$\begingroup\$ But what about something larger? \$\endgroup\$ – endolith Oct 29 '10 at 19:24
  • \$\begingroup\$ Might be okay to go larger, but not much larger. I've used a TO-263 on the current design but it was a bit too big. \$\endgroup\$ – Thomas O Oct 29 '10 at 19:28
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Maybe something like the LT1765-5.0 or the TPS54232? Both are SOIC-8, plenty of power and high frequent which makes for very small inductors. If you get regulators that only switch at 250kHz or even slower, you get rather large inductors (>47uH) for these applications. It also depends on how much current you are typically using , so read the datasheets properly.

Please note that the board design is very crucial if you're working with any type of switching regulator, but especially these regulators that switch at 1MHz or so.

What I also recommended to do with these regulators is to calculate the maximum power dissipation. I haven't checked the datasheets extensively so I don't know how much the SOIC-8 will have to dissipate. Usually a SOIC-8 package is terrible, and if the chip is available in something like a SOT263 (which cools much better - especially with planes) you will not be able to completely use the chip specs in that package (but it will still work to some extent).

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  • \$\begingroup\$ LT1765-5.0 looks very interesting, as does TPS54232, thanks for the links! \$\endgroup\$ – Thomas O Nov 14 '10 at 19:28
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Allegro A4447. Wide supply range and also pretty cheap. It has a thermal pad, but at low outputs you may not need to solder it, so can treat it as a normal SO8. Only possible issue is input voltage range at the low end - won't quite go down to 6v

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  • \$\begingroup\$ +1 for your research. But it needs to be 6V input minimum. This doesn't seem to be a very fast buck controller either, but maybe I'm missing something? \$\endgroup\$ – Thomas O Oct 29 '10 at 10:39
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Texas Instruments TPS 5410, although 68 uH inductor is recommended.

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  • \$\begingroup\$ It's a quite big inductor, I was looking at 20-30µH for most results. \$\endgroup\$ – Thomas O Oct 29 '10 at 19:40
  • \$\begingroup\$ Yes, that is true. Given the voltage and current you need, you may be able to use a smaller inductor than 68 uH but probably not as low as 30. See formula on page 12 of the data sheet. \$\endgroup\$ – Jonas Oct 29 '10 at 20:06
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Linear Technology LT1172CS8 appears too meet your criteria:

Is the 20SOIC package too big? ( LT1176CSW and LT1176CSW-5 )

Is it possible to tweak one of the "Black regulator designs" to meet your criteria? If you can't find a monolithic integrated solution, then you have no other choice but to build it up from discrete components like this.

May I ask what in the world you are doing that needs 5 W of power, but is so space-sensitive that a TO-263 package is "too big"? In my experience, tiny devices are typically micro-power, and devices that require more than 4 W generally have plenty of room for the TO220-5 through-hole or TO-263 packages that many switching regulators use.

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Semtech SC4524A looks a good fit 3-28V in, 2A out, SO8 (Thermal pad), up to 2MHz for small inductors/caps. Vary cheap.

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Check MP1584 out. This chip has a maximum frequency of 1.5MHZ and can deliver up to 3mA current. A friend of mine uses a module sold from china containing this chip to charge his tablet. The datasheet contains the inductor specifications and I can see all of them are less than 30uH.

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