ECL: Why'd they use negative voltages?
in [Design]
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From: krw on 7 Jun 2010 23:45 On Mon, 07 Jun 2010 18:35:58 -0700, D Yuniskis <not.going.to.be(a)seen.com> wrote: >krw(a)att.bizzzzzzzzzzzz wrote: >>>>> If you "slipped" when pulling/installing a chip, the legs >>>>> would vaporize before the power supply would even hiccup. >>>>> (needless to say, you removed all jewelry -- belt buckles, >>>>> eye glasses, rings, etc. -- when working on it) >>>> I worked on a test system that had a 100A -4V *linear* HP supply in it. The >>> The Vbb supply was a *shunt* regulator. A bunch of Lambda power >>> supplies driving a pair of *big* diodes "selected at test". >>> A colossal waste of power. >>> >>>> thing was the size of a small refrigerator. The other engineer did the 1600 >>>> pin pin-driver logic in proprietary ECL (-4V). I did the clock drivers in >>>> MECL 10K. I only needed about 50A for the 64 clocks. ;-) >>> This was the brains of a "600-pin tester". Programmable power >>> supplies to the UUT. Programmable thresholds for the input >>> comparators. 1ns timing resolution. It was just "insane". >> >> Yep, all that and 1600 pins. ;-) OTOH, it was a DC logic tester (clocks ran >> at system speed - 25ns). > >This is what soured me on stupid, brute force solutions to >problems. Nothing elegant about N copies of the same thing >over and over and over and over... Nothing elegant, but someone's got to do it. The clocking was fun.
From: Michael A. Terrell on 8 Jun 2010 00:55 D Yuniskis wrote: > > Hi Michael, > > Michael A. Terrell wrote: > > D Yuniskis wrote: > >> Hi Joel, > >> > >> Joel Koltner wrote: > >>> I realize it was the early '60s and all, but why does ECL generally use > >>> 0V for VCC and -5.2V for VEE, rather than, oh, say... 5V for VCC and 0V > >> You also had a Vbb of around -1.2V (?). Lines were typically terminated > >> to this. > >> > >>> for VEE? Something related to how things were done when toobs ruled? (I > >>> realize that you can almost always run ECL off of 5V/0V -- and > >>> apparently this was popular practice at one time?) > >>> > >>> And why 5.2V anyway? (Granted, 5.2V is no stranger than 6.3V filament > >>> transformers, I suppose...) > >> Dunno. But, it was fast and ate gobs of power. In the > >> mid 70's I worked on a processor (i.e., what nowadays > >> would be a CPU "chip") that drew 100A (MECL III and 10K). > >> "Bus bars" for power were 3/4" square copper shafts. > >> Instruction cycle time was 8ns. By comparison, I think a > >> 7404 (inverter) takes *7* ns just to change the state of > >> its output. > >> > >> If you "slipped" when pulling/installing a chip, the legs > >> would vaporize before the power supply would even hiccup. > >> (needless to say, you removed all jewelry -- belt buckles, > >> eye glasses, rings, etc. -- when working on it) > > > > You should have seen one of the first generation NTSC effects > > generator called the 'SqueezeZoom' It had a linear 5 V 1000 A linear > > power supply with a 208 three phase input. > > Yikes! I have no idea what the entire "tester" consumed > (my responsibility was primarily the CPU). We had a > dedicated service installed *just* for it, though. > Power cord took two of us to plug in (and twist-lock)... > some idiot mounted the outlet at eye level (not very > smart when you're lifting all that copper/rubber and > trying to mate the things). > > (sigh) As I said, disappointing to see such brute > force used. Even the UUT connection was by way of a > third horsepower motor driven "connector engagement > system". Though I guess it would be hard to do it > otherwise (today you could probably integrate much > of the electronics and get some huge wins from > just reducing the size of everything) How about a UHF transmitter tube with a pair of 1.5 V 1000 A filaments? They had to be balanced to 1/100 of a volt, so there was a pair of 'resistors' made out of 3" * 1" buss bar that was about 18" long. There was a large steel stud in each end. You used a wrench to tighten the nuts on one 'resistor' to adjust it, to balance the voltages. On the other end was a high current, water cooled 7 kV plate supply. Lots of places in old broadcast gear to cause an explosion, or to electrocute someone. :( -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
From: Jeroen Belleman on 8 Jun 2010 03:12 John Larkin wrote: > > 10KH type ECL does work fine at Vcc=5, Vee=0. That's called "PECL" > mode, originally "pseudo ECL" and lately "positive ECL". One generally > references all the signals to a nice 5-volt copper pour. I once designed a VME module with a lot of PECL with signals terminated into +3V, and which also had some circuitry running between +3V and GND. The +3V net was shared. Since the combined current of all the PECL terminators largely exceeded the consumption of the stuff between +3V and GND, I used a negative regulator with its input connected to GND to make the +3V. That raised some eyebrows, but it worked fine. Jeroen Belleman
From: John Larkin on 8 Jun 2010 11:06 On Tue, 08 Jun 2010 09:12:24 +0200, Jeroen Belleman <jeroen(a)nospam.please> wrote: >John Larkin wrote: >> >> 10KH type ECL does work fine at Vcc=5, Vee=0. That's called "PECL" >> mode, originally "pseudo ECL" and lately "positive ECL". One generally >> references all the signals to a nice 5-volt copper pour. > >I once designed a VME module with a lot of PECL with signals terminated >into +3V, and which also had some circuitry running between +3V and >GND. The +3V net was shared. Since the combined current of all the PECL >terminators largely exceeded the consumption of the stuff between +3V >and GND, I used a negative regulator with its input connected to GND to >make the +3V. > >That raised some eyebrows, but it worked fine. > >Jeroen Belleman It's fun to use regulators "upside down." We need a good bipolar-drive regulator. I use LM8261s for small stuff, and occasionaly LT1010s for bigger stuff. John
From: Joerg on 8 Jun 2010 12:05
John Larkin wrote: > On Tue, 08 Jun 2010 09:12:24 +0200, Jeroen Belleman > <jeroen(a)nospam.please> wrote: > >> John Larkin wrote: >>> 10KH type ECL does work fine at Vcc=5, Vee=0. That's called "PECL" >>> mode, originally "pseudo ECL" and lately "positive ECL". One generally >>> references all the signals to a nice 5-volt copper pour. >> I once designed a VME module with a lot of PECL with signals terminated >> into +3V, and which also had some circuitry running between +3V and >> GND. The +3V net was shared. Since the combined current of all the PECL >> terminators largely exceeded the consumption of the stuff between +3V >> and GND, I used a negative regulator with its input connected to GND to >> make the +3V. >> >> That raised some eyebrows, but it worked fine. >> >> Jeroen Belleman > > > It's fun to use regulators "upside down." > > We need a good bipolar-drive regulator. I use LM8261s for small stuff, > and occasionaly LT1010s for bigger stuff. > Check out the big fat audio amp hybrids. Of course, one has to be careful and pick one that isn't going obsolete next year because a particular car stereo was discontinued. Heck, if you want to go green on this you might even consider class-D. Then claim your carbon offset :-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |