Step-up DC-DC converter IC

I found an interesting voltage step-up IC. I wonder if anyone would like to comment on using it to power 4 white leds with 2 nimh batteries. It's right here:
http://dbserv.maxim-ic.com/quick_view2.cfm?qv_pk=1830

The central web site is http://www.maxim-ic.com

The IC is model MAX1700 or 1701

Looks like the input voltage is from .7 to 5.5v and then it steps it up to between 2.5 and 5.5v depending on how it's set up. Max current is 800 mA.

They give free samples too.

Hi!

The 1700 series is a good choice for our belongings.

If you want to take part in the step-up discussion, have a look in the thread "voltage regulators" in the LED forum.

Bye!

Yes, I see the thread over there. I'm starting to collect parts to build a step-up regulator using the Maxim 1700.

While I don't profess any technical expertise (I was an aero engineering major and only took one EE course), Zetex claims they have a step up dc chip that is suitable for LED flashlights. Search their website for the word "flashlight" and you'll find the ZXSC300 and ZXSC100.

Thanks. I'll go look around. I got the Maxim samples. They're a great design but the QSOP package is too small to hook to anything and I can't find a plug-in adapter. I'm thinking a DIP package would be better. Gotta be something out there.

From www.zetex.com I think the ZXSC300 is a SOT23-5 package and the ZXSC100 is an MSOP8. Both look to be very small, about the size of a ladybug. But ya, they're just right for an led power source if only there was a way to hook them up without special equipment in a lab.

The ZXSC300 is an interesting looking chip, but I couldn't figure out how to go about ordering one. Digi-Key distributes them, but their latest catalog doesn't list this chip.

Update: I did a search on the Digi-Key web site for the ZXSC300 and found it there, but they were sold out. I did find some very terrific news though. This chip sells for only $1.05!!! That is ¼-1/5 of the price of the other chips that I've been investigating! And not only that, but the components needed to use this chip are much easier to find than for the Maxim chips. Needless to say, this has piqued my interest. The only downside to this seems to be that this chip can only handle about half of the amperage as the Maxim chip, but it could still be very useful in lower load LED arrays.

I have some ideas:

1. http://www.loranger.com/ Here's a site full of chip adapters.

2. Maxim MAX757 is an 8 pin DIP (8/PDIP.3") It's not as good as the MAX1700 but it's a .3" DIP.

3. What do companies do when the want the breadboard a chip? I wonder if you can send a chip to someone and have it soldered onto a board or a larger size adapter that will plug into a socket?

Don't overlook the Zetex 100, it's plenty flexible and has a 1W output ... plenty for a moderate Nichia 5mm array ... it requires a minimum of 1.8v to operate. The Zetex web site has a good design note available for this chip that includes the PCB layouts (two-sided copper and silkscreen top).

To me, the ZX300's best benefit it it's abiltiy to work from a single or multiple cells. It's PDF files also contains a PCB design.

IMHO, the Maxim 1701 is better than the MAX1700. The 1701 works from a single or multiple cells and seems to me to compare favorably with the ZX300. I think the MAX1672 compares closely to the ZX100.

I haven't been successful getting samples of the other Maxim chips I requested (including the MAX752), so I don't think I'll be able to try them out.

It's been two weeks since I requested the Linear 1308's, and I'm beginning to think I'll have to (gasp) buy them to get to try them out.

Although I haven't finished my circuit cost estimates yet (missing shipping costs), it appears the Zetex circuits will cost about $4 less than circuits to accomplish the same tasks from Linear or Maxim.

Mark

Lufokc: Do you have any thoughts about making connections to ICs? I can't figure out how to do it. I've got a circuit diagram and two MAX1700s here in a little box. I'll go look around on the Zetex site.

I like to suggest you search the LED forum for information on soldering IC's. There are a couple of threads there that can help you out some. I believe there's one in this forum, too, but the others are far more extensive.

I've been searching for a used 5-watt soldering iron around town the past few days. That and a magnifying glass are going to come in handy. Even if I end up using silver epoxy, I think I'll need the soldering iron for some connections (my Weller soldering gun is overkill).

A bigger concern to me right now is making the PCBs. I'm looking at making six, each different. Each will require some very fine cutting with the Dremel ... some equally fine 'painting' with silver epoxy ... or doing it right in the first place and etching them. It's going to be a challenge, regardless. I don't think kludging the circuit together in a ball 'o wires will work well considering the tolerances these circuits demand.

Mark

I was hoping to epoxy all the tiny parts together and then run Silver epoxy "trails" to each connection with a tooth-pick. I don't know till I get all the stuff together exactly how hard (or even impossible) of a task that would be though. It seems from what I've read on the data sheets that the important thing to remember is to keep all the runs very very short. Whew, this project is a real challenge. It's a challenge tracking down all the components, it's a challenge sparing the $$ right now and then comes the ultimate challenge, putting it all together when I do get everything together…

Xcalibr8 - Jeff 1500 - Phantomas2002:

Don't all the chips we've been talking about and reading so much about require a ground plane? Doesn't that mean we pretty much HAVE to use a PCB?

On the other hand, as a fluke the kludge approach just might work ... maybe the circuit would just not be as efficient?

I don't know how to get epoxy to form the trails on anything but a flat surface ... wouldn't it just run on any other elevation since it takes so long to set up?

Xcalibr8 - If the kludge approach works once you get all the parts, please post!

Lord, yes these circuits are a challenge to do on the cheap as a hobbyist! It's taking forever just to collect the pieces.

Hang in there!

Mark

I thought I heard someone say that RadioShack had circuit boards for mounting SMD chips; solder chip to board, then solder on wires to pads for connections. If you ask me I think for the average hobbyist a DIP package and socket arrangement would be far easier to deal with. So which ICs are available in DIP?
Chet

Luffokc: Well, if the Silver Epoxy won't form the necessary trails then there is always the silver pen approach. That is exactly what a silver pen was designed to do. So far as putting the pieces together goes, I was planning on using normal 5 minute epoxy for that. I don't know if any of this will work, but it seems the easiest and by far the smallest configuration for a person, such as myself, that doesn't have all the fancy equipment needed to do it professionally.

Just for info, I think a step up circuit is called buck and boost.

Xcalibr8, you're not alone! I don't have any professional equipment to make the PCB's with either and I'm really hoping you have success so I can follow in your footsteps and NOT have to do PCB's. Making my own PCB's is a whole 'nother set of procedures I'd really rather not have to teach myself ... I just want circuits to drive some flashlights!

However, just in case the PCB route is the only one open in the long run, here are a few sites about building your own ...

How to make PCB's
How to make really, really good PCB's
Instant PCB Fabrication: Do It Yourself Probably the way I'll do it if it comes down to this
Making Printed Circuit Boards (he sends 'em out)

Jeff 1500 - sounds right to me.

chet - I haven't a clue what chips are out there in that size category. Yep, DIP would be MUCH easier to work with. Downside is size ... I want my circuits to fit inside a handheld flashlight.

Mark

Luffokc: Thanks for the links. Hopefully we won't need to go that route both for cost and size related issues, but it's good to have the links just in case. I'm sure that with as many bright (pun intended) people as we have working on this that we will prevail in the end. Where there is a will there is a way!

Hi guys!

Just FYI: A step-up is called boost, a step-down is called buck...

And for the PCB: If you use a stepup switching at several hundred kHz, you will need really TIGHT layout, you cant use lung wires. So I think the best way is to design your own PCD f.e. with AutoCAD and then glue it to the copper plane of a pcb with water soluable glue. Then use a dremel and a 0.5 mm drill (not drill, but I dont know the correct word, I mean the tool to put material away, not drilling) to take off the unneccessary copper.

I think there are really interesting discussions on this new part of the forum and I am sure, many of you will build a stepup in less than 4 weeks...

Bye!