Isolated variable resistor function?

modulation.

has

;-)

Bog standard? Not really. Not at that power level. It's all in the tuning.

Cost

is

to

network to gate.

As long as the processor is already there, tell them to stop whining. It's a SMOP and takes no resources. Even the validation is a piece of cake.

Is current flow in the resistor unidirectional... doesn't pass thru zero? ...Jim Thompson

Cost

is

to

network to gate.

No they won't. They'll think they're being useful ;-) ...Jim Thompson

modulation.

He he, right now I have one (OK not boost) running 30W@27MHz. circa 90% efficiency and passing EMC tests with flying colors (30dB margin first pass :-) The power Xtor is SMD, under a buck. The customer's designer is so p.....-..f (but he can't tell :-) that he insists on me reverting to an RF power Mosfet with all the implied mess, which I won't...

modulation.

though.

has

;-)

an

At 400W? Not a big deal there to get to 500kHz if you keep switching losses in check.

For a ZVS, yes, definitely. But you can usually only tune that for the upper ranges.

modulation.

has

;-)

Sure, one of the other engineers wants to go to a TO-220 but that scares the crap outta me and the cost of mounting eight of them isn't trivial either. The part I'm using (TI) is pretty good and well under a buck (at half-million ;-).

I ordered a couple of samples, just 'cause. I didn't know about Timer D until a few days ago, anyway. Curious about playing with it. I have a need to create tiny "runt" pulses in a signal and this might be usefully fast enough.

I need to check pricing. A fast PWM makes some things cheaper (such as living with an RC filter with sloppy 20db/decade rolloff) but if it costs a lot more then you lose the price benefit. There are a lot of ways of doing things.

Jon

If that's like what they were doing on their 28F3xx DSP parts several years ago, it's a regular ol' PWM followed by a variable time delay.

Which isn't to say that it's not a good idea, or an eminently workable one.

If it's for a voltage divider, what about a multiplying DAC? You'd still need the two wires to talk to it, but you could make whatever $$ vs. precision tradeoff your heart desired.

Running on the loophole frequency of 27.12MHz? It's been a long time but IIRC my highest resonant one was "only" 13.56MHz and on those frequencies it is very easy to pass EMC.

I wouldn't either, those RF FETs cost a ton and many don't come with SPICE models. Which is a big no-no for me.

Yes, unidirectional. Goes to zero at times but never crosses onto negative turf.

Wot's a SMOP?

I thought about a DAC of the old kind, with the switched and accessible R2R array in there. In essence that's almost the same as using a digital potmeter except it has better granularity. 6 bits would be plenty here though and digipots come in SOT23-5 and sometimes smaller.

Simple Matter of Programming. From the IBMJARG file:

SMOP n. Something quite possible, but requiring unavailable resources to achieve. "Why isn't that function available in the program?--It's just a Simple Matter Of Programming". (The implication being that, given a few person-centuries, all things are possible.) Also _SMOUP_ (smoop), a Simple Matter Of Micro-Programming (if hand-written, using a Greek mu).

Cheers

Phil Hobbs

Nope... No loophole there. It has to pass A class levels

Well, at these frequencies others spice models, mostly "designed" for SMPS are such a joke...

I had to do fire up the VNA, curve tracer,... and run my own one.

The hardest part was to find suitable air inductor makers in small quantities. I've seen quite a bit of horror stories there.

in

It seems likely to be a PLL multiplier, given my ignorance. As in what Atmel does for some parts, too. It only supports two integers (8 and 16) and that's pretty easy to do, as I understand things. (I think TI acquired Nat Semi (2011) and if so they got access to a VCO/PLL ranging up to 4GHz, too. Might not be just a coincidence here.) But you'd know better than I.

Jon

hehe. "than me." Darned dative case.

Jon

Not necessarily. I know what they did on one part years ago, but I haven't looked recently -- maybe they have figured out a clean way to do this that involves an oscillator running at 256MHz. It'd certainly solve a bunch of problems with variable time delays, even as it introduced a bunch of other ones.