ECL: Why'd they use negative voltages?
in [Design]
|
From: Jim Thompson on 7 Jun 2010 20:27 On Mon, 07 Jun 2010 17:16:06 -0700, Joerg <invalid(a)invalid.invalid> wrote: >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 >> 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...) >> > >As Jim said, noise immunity. But also from itself. The upper transistors > are the most prone to generate transients in ECL, so it helps if their >collectors tie right into chassis. In the old days 4-6 layer boards were >unheard of. All you had was 2-layer phenolic, and only if you were >lucky. Nowadays that's not an issue anymore because the +5V plane in a >PECL scenario is just about as good an RF sink as the ground plane. > >Why 5.2V I don't know but 6.3V is not an arbitrary voltage, just like >12.6V isn't. That fit the typical car battery voltages just right. So >you could hang the filaments straight onto the battery voltage and only >had to generate the plate voltages. That was initially done with a >mechanical switcher where the "buzzer cartridge" would wear out once in >a while. Original ECL had no current mirrors, just resistors, thus -5.5V gave the nicest (but still crappy) TC. Later on there was 10K/100K. My biggest challenge was making a threshold specification bracket overlay that would display automatically in PSpice simulations :-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: krw on 7 Jun 2010 20:27 On Mon, 7 Jun 2010 16:56:24 -0700, "Joel Koltner" <zapwireDASHgroups(a)yahoo.com> 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 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?) Add to the above, shorting the common emitter outputs to ground isn't damaging. >And why 5.2V anyway? (Granted, 5.2V is no stranger than 6.3V filament >transformers, I suppose...) Stack up the voltages (don't forget the AND gate). Not all ECL was the same, though. Our high performance ECL ran off +1.25V and -3V, with the outputs around ground.
From: krw on 7 Jun 2010 20:28 On Mon, 07 Jun 2010 17:16:06 -0700, Joerg <invalid(a)invalid.invalid> wrote: >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 >> 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...) >> > >As Jim said, noise immunity. But also from itself. The upper transistors > are the most prone to generate transients in ECL, so it helps if their >collectors tie right into chassis. In the old days 4-6 layer boards were >unheard of. All you had was 2-layer phenolic, and only if you were >lucky. Nowadays that's not an issue anymore because the +5V plane in a >PECL scenario is just about as good an RF sink as the ground plane. > >Why 5.2V I don't know but 6.3V is not an arbitrary voltage, just like >12.6V isn't. Of course not. 12.6V is twice 6.3V. ;-) >That fit the typical car battery voltages just right. So >you could hang the filaments straight onto the battery voltage and only >had to generate the plate voltages. That was initially done with a >mechanical switcher where the "buzzer cartridge" would wear out once in >a while.
From: Joel Koltner on 7 Jun 2010 20:29 "Joerg" <invalid(a)invalid.invalid> wrote in message news:875gebFf6oU1(a)mid.individual.net... > As Jim said, noise immunity. But also from itself. The upper transistors are > the most prone to generate transients in ECL, so it helps if their > collectors tie right into chassis. In the old days 4-6 layer boards were > unheard of. All you had was 2-layer phenolic, and only if you were lucky. Ah, gotcha -- that makes a lot of sense. "Ground is ground, but 5V (or 5.2V or whatever) tends to 'wiggle around' rather more..." (Especially in that the earlier ECL series where VBB wasn't actively regulated against supply voltage variations.) > Why 5.2V I don't know but 6.3V is not an arbitrary voltage, just like 12.6V > isn't. That fit the typical car battery voltages just right. Hmm... 13.8V = car running w/alternator floating a 6-cell battery and 12.6V = car turned off, battery powering radio then? Thanks, ---Joel
From: Jim Thompson on 7 Jun 2010 20:31
On Mon, 7 Jun 2010 17:25:20 -0700, "Joel Koltner" <zapwireDASHgroups(a)yahoo.com> wrote: >"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote in >message news:ot1r06hc3e8adqh07qc8ng6un6ftm2u68q(a)4ax.com... >> I was there when they (Narud, Seelbach, Philips, et al) did that. > >Was the whole idea (just keep the transistors operating in their linear >regions rather than saturated or cut-off -- Yep. Current mode is fast... better power-speed curves than CMOS at really high speeds. >sacrificing power consumprtion for >speed) pretty much self-evident to everyone at the time, and it was just a >question of convincing enough people of the viability/marketability of the >technology so as to get the money for funding all the development -- or was it >instead a pretty novel idea, that few people had really thought about and >developed up until that point? > >Thanks, >---Joel It was military funded: Wright-Patterson funded all my flash ECL A-to-D's. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy |