Voltage to PWM chip (similar to class D)?

I guess I'm not really following all this. You have a control circuit that is not easy to do with analog chips and yet you don't want to use a digital control. From the bits and pieces I am seeing I believe a classic ADC-DSP-DAC would suit this problem very well. Forget the silly PWM thing and all the goofy filtering problems. I only call it silly because in this design it doesn't seem to fit very well. With a pretty basic digital path you could do the whole thing in one chip even. I believe ADI makes some devices intended for exactly this although I've never used them.

Or maybe I'm still not following what you are trying to do.

I could recommend a chip that could handle this *very* easily, but if you think an FPGA is hard to program, this would blow your mind!

It was a cutting-edge FPGA in the mid 90's. With ASICs you can get much more design security. The trick is to pick a foundry you trust and a run-of-the-mills process that is used for tons of other products. By going directly to the foundry you are cutting out one middleman (the FPGA vendor) and thus reduce the overall risk.

An example for the longevity of semiconductor processes: We just started something on a 4" wafer. Those date back almost to the days of Methusaleh yet it's no problem. If a process is also used to make mil stuff, chances are it'll survive both of us.

And I might. Plus opamps/comparators.

I pretty much only used the 8051 when I was allowed to decide. Clients have used Atmels and also PICs that have lasted a long time but I don't have production data for those products.

There is one other method but it requires you to be an important enough customer: Negotiate a deal where, in case the product is ever obsoleted in the first half of this century, you retain the right to have it made at a foundry of your choice. For that, all the GDSII data goes into escrow at some law office. It'll never come out of there if they stick to their promise. But if they don't or if they go belly-up, it does.

I am pretty sure they will supply. They told me so and they've never lied to me. Their prices are on the high side anyhow and I don't think they would jack up the price on customers.

Got to stay with multi-sorce packages like 44 QFP.

They _are_ making 100MHz 8051. No kidding. If it ain't got enough horses use a 2nd one :-)

This is one reason why I try to keep things simple. Many jobs that are done with a DSP can be done without. But not all of them, of course. Of course, for me that's easier to say than probably for you because I do mostly analog stuff. Sometimes it's the whole architecture though and then one of my fuirst questions to the client is about parts sourcuiing and longevity.

Generating a PWM stream with down to 1nsec granularity that way would be increadibly power intense and expensive.

I haven't found any, only delta-sigma which doesn't fit too well here.

I am pretty sure there are FPGA that can do this but not alone, they must have an ADC up front because the control is analog (not my choice, it's a requirement).

It isn't a problem at all doing this analog. I can use any old PWM chip or one of those TimerBlox from LTC, hang an error compensation loop around it and call it a day. Two ICs and a sprinkling of discretes. And I will do that if there aren't any suitable single-chip class-D audio solutions.

Nope :-(

Unfortunately that would put a serious crimp into the versatility of the product.

Yup, I've used them but they aren't precise enough. Also, they don't work well for PWM, just for V/F anf F/V.

T'is exactly what I am looking for and why I posted here :-)

If you think that money (and time) invested has nothing to do with "risk", perhaps. That's a rather Democratic view of economics, though.

Crap! That must have been 1960. ;-)

The 8051s of today aren't your grandfather's 8051s, either. I'm trying to push the ARM-Mn as the microcontroller for the future. We just switched to AVRs but there are a lot more choices in ARMs. If the code is written properly, porting to a new processor isn't a big deal.

Use Automotive parts. They're committed to making them for at least a decade. Of course that assumes you don't pick one that's already been around two. ;-)

ADI hasn't stung us either. On the other end of the spectrum, I wouldn't touch Maxim with Barak Obama's pole. Others do, and like them. they do have some interesting parts but I *have* been bitten.

Huh? Going ASIC took a lot of risk out of this process. Instead of depending on an FPGA manufacturer who is depending on a foundry we were then only depending on a foundry.

Yeah, I was surprised myself. But all the places we are using for the various fab steps consider that standard fare.

Yes, but it's a re-layout and in many regulated environments you must go through the whole big validation process again.

Or was specifically made for a car series that then gets discontinued in two years. That is a problem with parts for consumer electronics sucha s TV sets. I never use them anymore.

Oh yeah, some clients have been stung, big time. OTOH that has brought me several "design-out" assignments that then turned into longterm client relationships. One lasted all the way until the company owner died.

You don't think significant NRE *ADDED* risk? You have a real funny CFO.

Seriously, I thought everyone had gone to at least 6" wafers decades back. It's been over a decade since the digital guys went to 12" (300mm). Of course, 8" are still common for jelly beans.

Not just layout but does anyone make a 12-clock, 12MHz 8051 anymore? ARM *is* the way forward.

Name one (an ASSP, not an ASIC). Even if it's only in one car series, it'll have at least a 10yr life, though if you only want one don't count on any part being available in a decade.

The company died with him? Of course the federal government wants that to happen but it is still pretty poor planning.

Pouring it into an ASIC was not very onerous in terms of NRE. Plus we could easily amortize it. It paid for itself in a jiffy anyhow because the ASICs were much less expensive.

That's what I thought as well. Until the end of last year. To me that was like going to a car dealer and finding brand new 1956 Bel Airs.

You can but there is no law against using a 25MHz or whatever version with a 12MHz clock.

I might use my first one this year. Pondering which one to pick, one that has good audio connectivity. Still got lots of time, maybe it'll be the M4F series from TI. I was eyeing an AD Sharc but after a sobering awakening with their seemingly outsourced "support" I decided not to.

I don't remember, too long ago. Mostly TAA, TBA and TCA series chips. I haven't used them but clients have and then got burned.

Kind of. His widow ran it for another year or two. It is good not to make any drastic asset changes right after a spouse passed away but eventually she sold the company. It was a smart move on her part.

You can't always avoid it. Sam's Town was a local Western style entertainment city right in our village (Cameron Park). Mostly for kids and many Bay Area folks fondly remember that from trips to Lake Tahoe, when dad pointed his Studebaker towards the off ramp. Death taxes killed it, along with over 150 well paying jobs. Those jobs never came back and the place was bulldozed. Dems do not understand this stuff.

It had to have been a trivial part. ASICs are unaffordable for all but a few applications. Really, they're only interesting when there is no other choice (rather the same for FPGAs but on a whole different level).

OK, now it's clear that you're been working in Cuba. ;-)

Well, then it's not a 12MHz clock. ;-) The greater issue is the

We're in pretty deep with Atmel on their M0 and M4(ish) products. Sharc is a DSP and isn't really much good as a controller. Very expensive. We use a lot of them, in fact I'm using a 41279 and 41269 on a board I'm doing right now. For a cheaper DSP, the Sigma is pretty good series (using one of them on another board that I've just sorta wrapped up the schematic). Each board also has one of the Atmel ARM Mn processors for the mundane stuff.

More information?

Probably a good idea but that still shouldn't kill the company.

Death taxes have to be covered by insurance. But, that's what the lefties in government want. They have to kill wealth. "It's only fair."

ADI just killed ADG465. It wasn't an especially old part... they just didn't make enough money off it. Damned nuisance.

Absolutamente no. It does screaming fast image processing. No competitor ever managed to rival it and they tried hard.

I have to disagree because I've been involved in a few ASIC projects. If it's just pouring existing FPGA logic into an ASIC that can be done in the high five digits. An ASIC from scratch is around half a million after it's all said and done, depending on design complexity. Peanuts compared to the savings or other upsides it provides.

:-)

Are they still making them?

Not all of them. Software regression testing, yes. EMC approvals usually not. But if you are plopping in a Testarossa-series modern MCU then you get to do the whole enchilada, again.

Those were projects back in Europe, last century. Most of that is gone. One of the TCA-sumpthins was for electric drill speed control and I believe then the drill series was discontinued. But really, it's too long ago to say for sure. Lots of audio and RF/IF chips as well. They suddenly became unobtanium.

Oh, it hasn't. But the new owners haven't used me (yet). AFAICT they still produce my designs.

What?

Yep, and then they kill scores of jobs like here in California. Seems they don't even do exit interviews which could reveal so much. Well, maybe they want to hide how much damage they are doing.

Arrow and Newark still have some. Farnell has stock in Europe and Asia but often Newark stock seems to be physically the same as Farnell Europe. Mouser has a few thousand as well. So at least there's opportunity to stockpile.

the dsPIC33 has ~1ns resolution PWM and a 10 bit 2Msps ADC, $1.69 if you bu y 1000

-Lasse

How does it do that when the on-chip VCO for system frequency is spec'd between 100MHz and 200MHz?

Silicon delay wouldn't be so nice.

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u buy 1000

never used it so I don't know, look like you have to set it for 120Mhz to g et 1.04ns resolution

why not?

I guess if the VCO is done with ring oscillator there is already a string you can tap to get the extra phases for free

I believe Xilinx does something similar servoing of delays for their IO delays

-Lasse

Maybe you don't strictly need PWM, but would be able to use sigma-delta a modulated bitstream instead. In that case you could perhaps use this one, though it comes with galvanic isolation that you might not need:

Otherwise if you really need PWM, what if you wrap feedback around the LTC6992, i.e. invert and square up its output by putting the PWM through a CMOS inverter running from a very stable power supply, and then use resistors to add the inverted PWM waveform to the incoming input voltage, and call the sum the "error voltage". Theoretically the average of this "error voltage" will be exactly mid-rail. Use an op-amp to integrate any deviations from mid-rail and feed that into the LTC6992, to correct it. Perhaps two op-amps would be needed as integrating circuits tend to invert, which you might not want here.

Chris

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OK. Instead of a strict linearity perspective can we look at it from a settling time perspective for various portions of step size from minimal to full scale?

?-)

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spectrum.

Does it HAVE to be PWM? Can't PFM do the job?

I had noticed.