Monolithic DC/DC converters

I think the biggest plus with monolithic parts is that you save design time and grief on the manufacturing floor. You slap them on the board, and if something goes "pffft" you point at the manufacturer and say "FIX!".

Then you pay for it, compared to the BOM cost of building one yourself.

If it is a mass produced product you should stay discrete but find a more compact solution.

I use monolithic converters if I need isolation or when production batches are small.

EMI can be an issue. Anything that ventures outside the enclosure has to be filtered pretty well.

...or time short. These things tend to be rather noisy, too, so that can be a consideration. The biggest problems I've had is radiation via cables. These things (particularly the cheap ones) tend to make that problem worse.

It's always better (cheaper) to reuse existing designs, either in house or out of house, assuming the existing design meets or slightly exceeds requirements. Existing designs that are overkill need to be evalated.

What do you mean by "monolithic DC/DC converter"? Got a link to one?

John

Good point. I was assuming he meant anything that comes manufactured as a module, that you thump into a board as if it were an IC. I've used the ones from TI with the 78xx-compatible pinout, although that was a project that never got beyond the prototype stage.

Here's one (but I don't think it's what he was referring to ;-).

It also depends on if the converter is "standard".

We use an LCD Vee generator of -22V.

We can not build a converter cheaper then we can buy, there are just too many out there. Size is not a problem ;-) .

As the OP did not state what his converter is use for, who is to say if DIY is cheaper.

hamilton

I think this is what the OP is talking about:

Sure. I've used them. I was just answering John's challenge for a "monolithic DC/DC converter". He knows about the ADI iso-power stuff, too. I was just tweaking him. ;-)

This is an example what I had in mind

The inductor and capacitors are integrated in the package, only a few external components are needed.

Thanks for your answers by the way.

Actually making quite a bit of use of that exact part. They're a bit pricey, but the outputs are beautifully clean and they're certainly easy enough to use. The only note on them is that they're non-synchronous switchers, so you'll see some efficiency hit if you're doing big step-down ratios to low voltages.

I *GUESS* they're pricey! $16.90 to $34.58 in DigiKey.

• labor.

Hope This Helps! Rich

That's insane. Direct from LTI, single piece pricing is about $12.

MAX says we're paying $9.94.

ftp://jjlarkin.lmi.net/LTM1.jpg

ftp://jjlarkin.lmi.net/LTM2.jpg

ftp://jjlarkin.lmi.net/TEM2_Power.JPG

On that last board, the things near the connector are my home-made current shunts.

National has something similar in DPAK sorts of packages, which would be easier to place and especially rework, if you don't have a lot of surface-mount gear.

John

Excuse my ignorance, but what is LTI? I could use a lower-cost source for components...

L_inear T_echnology Corporat_I_on. (direct sales).

Best regards, Spehro Pefhany

Many thanks, Sphero...