basic ECL question

Hello Mike,

problem

So who dunnit? ECL wants to see a nice termination or a line with a matching termination. Anything deviating from that can look like an L, C or worse to the ECL chip. On a wire wrap board we even had an FM radio go completely silent when the designer fired it up. Oops. The trace on a fast scope coupled in with a loop looked like a wild rodeo. It was singing from all kinds of places. Then we did it again as a soldered board with the wires neatly fastened to the plane and twisted. Now it was clean like a whistle. Same with the layout.

I have also seen on oscillating ECL driver on a neatly laid out board. They hadn't stuck to the stripline formulas too religiously, or probably not at all. So we did the layout again, same pattern but correct trace widths and no more 90 degree bends. Then it worked fine. I guess that must be the reason why the ECL data books contain the impedance calcs for traces.

Regards, Joerg

ECL sure is fun, isn't it? Each version from MECL 1 on up has it's own characteristics, and you can do things in one family that won't work in the next. I used to love cascading differential line recievers for fast amplifiers and comparators, but that came to a screeching halt with the latest version of EclInPsLite. Too much gain and bandwidth in too small a package.

Otherwise, I haven't seen any problems with layout or oscillations except with that single example I mentioned. It was the window generator for a disk drive data recovery channel, and had extremely short leads to the next chip with 50 ohm pulldowns. No reason to go squirreley but it did.

As far as right angle bends, things are a lot better now than they were with rubylith. I had one layout girl get so exasperated with me that she packed up and walked out when I asked her to move an ic:) She came back the next day and eventually headed up my cad department.

Howard Johnson has some thoughts on 90 degree bends - he shows they are not helpful below about 2GHz:

Doug Brooks at UltraCad did some measurements that seem to indicate the same thing:

This all changes with GigaComm ecl, but in the meantime the main benefit may be to keep dirt from accumulating in the corners:)

Mike Monett

[...]

Thanks, John. With you and Jim recommending them, how can one go wrong?

Mike Monett

Hello John,

$35, ouch. Do they come in leather pouches, each with their own royal birth certificate?

Yes, I also found that ECL runs well behaved. Unless people forget how fast it is. A few nano henries might not matter with TTL which is what most of the guys had been used to. For ECL it matters.

It probably wouldn't have been an issue with this board. But while cleaning up the transmission line stuff I thought we might as well do it by the book. The boss there actually said later that round edges don't really look "high tech". Since I was a consultant I had to hold it at that point...

Regards, Joerg

may make the

tape-ups ! Curvy

Nah. That stuff was obsolete long ago. Real layout is done with rubylith and a sharp knife.

Then the little snipped pieces can lay across some traces on an internal layer and give you a short under an expensive ic:)

Mike Monett

problem

90 degree bends look real shit though and provide stress to the trace that may make the board less tolerant of mechanical forces. Ahhh for the days of manual tape-ups ! Curvy tracks...... I loved doing them. You get better board density that way too.

Graham

I've seen a trace break ( often ) at the transition between the trace and a pad. Tricky to spot too. Can't be sure about 90 degree corners.

Well, actually I don't miss it either. Board layout was certainly more of a true art back then though. I have a tote box full of old tape and patterns. Damded computers - lol ! I used more Circuitape, Brady and Chartpak though.

Graham

Hello Mike,

Didn't he also start an Inn & Restaurant chain? ;-)

I love it when he says that some people must be afraid that a few electrons fly off the trace in a bend and into space. But I guess he didn't write this when EMC rules came into being and some covered the frequency range above a GHz. I wonder what an electron ambulance looks like that picks up the ones that didn't make it around the 90 degree bend and crashed.

And hair cracks from developing.

Regards, Joerg

Hello Graham,

make the

! Curvy

To the RF guy they look like the curves of a Stradivari violin.

Manual taping looked good until you went closer with a magnifier and saw the tape crinkling at the curves. Especially when it was hot. That is where a lot of the under-etching happened.

Regards, Joerg

Four people can have access to tons of money and know-how.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

That's right. There are actually _multiple_ fabs in use, depending on product line or ASIC.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

How would AZM benefit? I can't divulge, but I know, all the different foundries in use by AZM... they are numerous. I note many of the FSA members don't actually qualify as fabless _businesses_, they're just filling their internal needs... I know because I do design work for a number of the members ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

You can't get samples out pretty cheaply by going thru a MOSIS "shuttle" or MPW (multi-project-wafer) run.

Production usually means $60K to $100K to cover masks and maybe 5 wafers.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Crap! Typo! Make that...

You CAN get samples out pretty cheaply by going thru a MOSIS "shuttle" or MPW (multi-project-wafer) run.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Sure. See, for example, the Fabless Semiconductor Association (FSA) (clickable) membership list:

But Arizona Microtek don't seem to be members.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Tell them that they'd make a bundle if they got you to design a decent ECL comparator for them. I can provide the specs.

John

I did that already. Back in the '60's... MC1650/51

But you might suggest that to Harald Muller anyway ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

They probably wouldn't enough to make it worth the $5K or $10k/year.

That list is still surprisingly (to me) long. I've been sort-of aware of fabless companies, but never noticed how many there are, especially in niche markets. Like this one:

About how much money would they have to pony up to get that one product out the door (production, not samples)? Supposing the design was free/sweat equity, for the sake of argument.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Hello Spehro,

Plus the fab can be elsewhere and they don't have to run or even own it.

Regards, Joerg