Synchronous Switchers

I like to discuss electronics with people who know something about it. JT defines such people as sycophants.

Neither of you seems to have anything to say about synchronous switchers. Hens seldom do.

I think not.

Engineer.

Evil!

The inductors are "shielded", according to the data sheets. There is some external field that I can see with a sense coil, but it's essentially a square wave.

I have a small Coilcraft air-core inductor on the end of a hank of coax.

I really think the EMI is from shoot-through current spikes in the switcher chips.

If you are not familiar with this site,

you could peruse his articles to see if any of his measurement techniques would suit you.

Cheers, John

Nope. I don't think any of these clowns can "ps..." >:-|

square

His stuff is OK, pretty basic, but he wants to sell seminars so he's careful not to give much away.

In the ~20 years that I did department manager duty I never had sycophants... I purposefully hired guys with enough talent and ambition to covet _my_ job.

But sometimes I've been astonished by past employees, as in this E-mail from a month ago (from an employee of the mid-90's), that damn-near made me cry...

"Hi Jim, How are you doing? I was just sitting here thinking about you. I do that often. Today I was just reminiscing over my career. I've got this young pup working with me who is really, really good. I keep thinking about how difficult this job is when you don't have a mentor and that reminded me of you. I truly miss the days when you were my mentor. I felt like there wasn't anything I couldn't do. I learned a great amount from you. You've helped me through many tough times. I really wish I was still working with you. I don't think I'm cut out to be the top dog. So, I'm just writing to say hello and thanks for all you gave me. Xxxxxxx X. Xxxxx P.S. Sorry I'm not a very elegant writer."

:`( ...Jim Thompson

Gosh, what a sweet, wonderful person you are. Between episodes of revenge and murder fantasies.

Most of the better switcher control chips have anti-overlap thus anti-shoot-thru built-in.

Though it's likely that Larkin is clueless on how to use it properly

...Jim Thompson

My bad. I missed the pun :-( ...Jim Thompson

Hey, it works. First try.

I kind of liked it. It includes a variation on a Hobbsonian photodiode bootstrap circuit that speeds up the EUV photodiode response by about 4:1. Since the customer hadn't heard of that trick before, they were impressed.

Show us some electronics that you've designed lately.

This kind of "shielded" inductor leaks a little B field, but that will make a modest small-diameter symmetric circulating current in the solid copper ground plane. Any resulting sheet currents will be microscopic on the other end of the board. And I'm not seeing the fundamental switching frequency, which is the dominant inductor current (and the measured dominant B field), but higher harmonics. So the effect isn't magnetic. The biggest inductor, with the highest current and biggest leakage field, is on the +5 volt nonsynchronous SimpleSwitcher, which isn't causing EMI problems.

Why would I want to shoot down my hypothesis? What I want to do is get the spurs down and make this customer happier.

We're out of bare boards, sold the last batch, so I may as well spin the layout before we order more. The pragmatic thing to do is replace all the switchers with LTM8023 modules. They have everything onboard, including i/o caps and the inductor. The architecture is classic buck, PNP switch and schottky catch diode. They are very quiet.

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bootstrap

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bootstrap

Larkin should show us a circuit worthy of critiquing. Otherwise his utterances have to be considered strictly as demented theatrics.

I'll make Larkin (and his sycophants) an offer any _good_ engineer wouldn't refuse...

I'll provide the wine and cheese.

Also the whiteboard, and video camera.

To perform before a panel of questioning peers (all MIT grads, but not me * ... Larkin would claim I'm cooking the books). Larkin will have to sign off that he authorizes his "performance" to be shown on YouTube.

(* I do claim the right to provide the "laugh track" >:-}

I await Larkin's reserving his space (and authorizing the YouTube video). (I'm not holding my breath ;-)

Anyone else refuting my technical competence is also invited... same rules apply... actually a few more rules: (1) Positive ID and (2) Identifying your employer... your employer will get a personal copy of the video :-)

It's time that we separate the name-callers from the competent. Posters name-calling in response to this post will be sought out and horse-whipped. Think I bluff? Try me. ...Jim Thompson

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