On Tue, 31 Jan 2017 19:48:18 -0500, "tom" <tmiller11147@verizon.net> wrote:> >"John Larkin" <jjlarkinxyxy@highlandtechnology.com> wrote in message >news:17929cpj3lgerjo5mmfnjm0dvbn5ee1i9g@4ax.com... >> On Wed, 1 Feb 2017 10:31:28 +1100, Clifford Heath <no.spam@please.net> >> wrote: >> >>>On 01/02/17 09:31, John Larkin wrote: >>>> The Onsemi NL37WZ16US buffer is a nice part. Put all three gates in >>>> parallel, run at abs max Vcc, source terminate at maybe 40 ohms, and >>>> it's a vicious sub-ns output driver. >>> >>>What's the best edge-time you've seen from these TinyLogic parts? >>>Got a plot handy? Better than an LVDS driver? >> >> This flipflop rise time is the fastest I've seen, 150-200 ps sort of >> range. LVDS edges are fast, but the voltage swing is small. >> >>> >>>I want to build (hobby) a cheap TDR circuit, what's the best >>>driver approach to get into the 100ps vicinity? (similar speed >>>sampler needed, of course). >> >> A step-recovery diode is the conventional way. Some are cheap. I think >> MA44769 is still available, SOT23, under a dollar. Phil and Joerg have >> made fast pulses with cheap transistors too. >> >>> >>>I keep collecting ideas from you and Phil, but haven't built >>>anything yet... I lack test equipment to look at this stuff, so >>>need something that can verify its own behaviour. A little more >>>help would be welcome. >> >> Picosecond electronics is fun. If you really want to get into that, >> get a sampling scope from ebay. The investment is low hundreds to low >> thousands of dollars, depending on bandwidth. >> >> Old Tek and HP manuals are enormously educational. >> >> >> -- >> > >The Tek 11801/11802 sampling scopes can be had for very low cost. > >Here is one for $150 plus $111 shipping that is showing errors. The repair >is almost certainly a pair of dead memory NVRAM packages and would run about >$30 to restore.If the error code is E5622, the most common one, the fix is to replace the sram things in the bottom. That's easy. https://dl.dropboxusercontent.com/u/53724080/Sampling/11801/11801_fix.pdf> >http://www.ebay.com/itm/H133984-Tektronix-11802-Digital-Sampling-Oscilloscope-/391662629720?hash=item5b30e97358:g:1KkAAOSwEzxYQgcd > >These are really amazing scopes if you are interested in the ps world. With >a SD24 sampler module, you can do TDR in the millimeter range. And two >channels for differential measurements. > > > >I have maybe 10 of the mainframes and a couple dozen heads, worth a fortune at the original price. Beautiful instruments. My personal scope is an old b+w 11802, which takes nicer pics than the later color versions. It will internal trigger, too, with the delay lines. Anybody interested in picosecond stuff should get one of these. They do weigh 50 lbs or so. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
insane flipflop measurements
Started by ●January 31, 2017
Reply by ●January 31, 20172017-01-31
Reply by ●January 31, 20172017-01-31
On Wednesday, February 1, 2017 at 9:01:28 AM UTC+11, John Larkin wrote:> On Tue, 31 Jan 2017 00:22:23 -0800 (PST), "John Miles, KE5FX" > <jmiles@gmail.com> wrote: > > >On Monday, January 30, 2017 at 8:08:21 PM UTC-8, John Larkin wrote: > >> That fall time is amazing, but the rise time is hard to believe. I > >> can't see that I'm doing anything wrong. > > > >Neat, the data sheet says Tr = 2.5 ns. > > > >Photo of test setup? > > > >-- john, KE5FX > > Here's the breadboard. > > https://dl.dropboxusercontent.com/u/53724080/Parts/Logic/NC7SV74/NC7SV74_test.JPG > > I didn't expect it to be so fast, and the carbon film resistor pickoff > from Q to the scope is maybe questionable.Very. L-trimmed surface mount resistors have much less inductance and parallel capacitance. <snip> -- Bill Sloman, Sydney
Reply by ●January 31, 20172017-01-31
Am 01.02.2017 um 00:31 schrieb Clifford Heath:> On 01/02/17 09:31, John Larkin wrote:> I want to build (hobby) a cheap TDR circuit, what's the best > driver approach to get into the 100ps vicinity? (similar speed > sampler needed, of course).Analog Devices ADCMP580 CML output comparator. (maybe adcmp590 or so, I cannot check it here). I do like CML! < https://get.google.com/albumarchive/103357048842463945642/album/AF1QipNilhbbnpm11i4xnlIgrmH6gt_TEYRtCwlIq5Nw/AF1QipOA07ifIcPnTb7NtoSfI118O4T5RSvhECQ1YEso > I had faster ones, but they are not on the open market. Laser drivers. (JL, sorry if I happened to shock you, but note the half year waiting time for the ON semi parts!) Gerhard
Reply by ●January 31, 20172017-01-31
On Wed, 1 Feb 2017 03:29:12 +0100, Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> wrote:>Am 01.02.2017 um 00:31 schrieb Clifford Heath: >> On 01/02/17 09:31, John Larkin wrote: > >> I want to build (hobby) a cheap TDR circuit, what's the best >> driver approach to get into the 100ps vicinity? (similar speed >> sampler needed, of course). > >Analog Devices ADCMP580 CML output comparator. (maybe adcmp590 or so, I >cannot check it here). I do like CML! > >< >https://get.google.com/albumarchive/103357048842463945642/album/AF1QipNilhbbnpm11i4xnlIgrmH6gt_TEYRtCwlIq5Nw/AF1QipOA07ifIcPnTb7NtoSfI118O4T5RSvhECQ1YEso > > > >I had faster ones, but they are not on the open market. >Laser drivers. > >(JL, sorry if I happened to shock you, but note the half year waiting >time for the ON semi parts!) > > > >GerhardDigikey has a couple hundred in stock. We have most of a 3K reel. We use it as a mosfet or phemt gate driver too. It's a pretty good deal for 16 cents. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●February 1, 20172017-02-01
John Larkin wrote:> > > I'm doing a fast thing and thought I might go all CMOS, instead of > traditional expensive ECL. We have the Fairchild NC7SV74 tiny logic > flipflop in stock, 16 cents each. I thought I'd play with one. > > Here are the rise and fall times at the Q output, 3.3 volt supply: > > https://dl.dropboxusercontent.com/u/53724080/Parts/Logic/NC7SV74_2.JPG > > That fall time is amazing, but the rise time is hard to believe. I > can't see that I'm doing anything wrong. > > The clock rise to Q rise prop delay is 0.8 ns. Its temperature > coefficient was hard to measure, but it looks like maybe +0.7 ps per > degree C. Vcc delay coefficient is so close to zero that it doesn't > matter. > >Change the circuitry to have balanced Q/_Q drive to two otherwise identical in layout parts and look at the outputs. Betcha you see decidedly different timings. Then swap the layouts and note that difference essentially does not change...
Reply by ●February 1, 20172017-02-01
"John Larkin" <jjlarkinxyxy@highlandtechnology.com> wrote in message news:ig129clsgk8b431usgjsk8tccbek93p0lv@4ax.com...> I didn't expect it to be so fast, and the carbon film resistor pickoff > from Q to the scope is maybe questionable.Maybe. But then why is the one edge reasonable? Is its true rate appallingly slow (>1ns)? What does it do between SET and (D=0) CLK? Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reply by ●February 1, 20172017-02-01
On Wed, 1 Feb 2017 03:38:12 -0600, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:>"John Larkin" <jjlarkinxyxy@highlandtechnology.com> wrote in message >news:ig129clsgk8b431usgjsk8tccbek93p0lv@4ax.com... >> I didn't expect it to be so fast, and the carbon film resistor pickoff >> from Q to the scope is maybe questionable. > >Maybe. But then why is the one edge reasonable? Is its true rate >appallingly slow (>1ns)?The falling edge, the slower one, is 488 ps. The rise seems to be genuinely about 200 ps, using the HP probe.> >What does it do between SET and (D=0) CLK?I'm not planning to use SET, but I'd expect it to be similar to clear. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●February 1, 20172017-02-01
On Tue, 31 Jan 2017 00:22:23 -0800 (PST), "John Miles, KE5FX" <jmiles@gmail.com> wrote:>On Monday, January 30, 2017 at 8:08:21 PM UTC-8, John Larkin wrote: >> That fall time is amazing, but the rise time is hard to believe. I >> can't see that I'm doing anything wrong. > >Neat, the data sheet says Tr = 2.5 ns. > >Photo of test setup? > >-- john, KE5FXI don't see a Tr or Tf spec in the data sheet. The 2.5 ns, in one figure, seems to be a max for the clock input. Tr and Tf are seldom specified for logic or FPGAs. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●February 1, 20172017-02-01
Tim Williams wrote:> "Jon Elson" <jmelson@wustl.edu> wrote in message > news:oMWdnUjCoLgObg3FnZ2dnUU7-bnNnZ2d@giganews.com... >> Watch out for the shoot-through current on fast CMOS parts. I did a >> design >> some years ago, mixed-signal stuff, and had insideous crosstalk issues. >> After realizing what it might be, I discovered the single-gate and >> single-FF >> parts had a shoot-through of about 0.5 - 1 A that lasted about 3 ns >> (might have been shorter, that was the best I could resolve with the >> scope and probes I was using.) > > Hrm, curious how you measured that? >This thing was a 32-channel "discriminator" for nuclear signals. It had two comparators and a scheme to compare a delayed and attenuated signal with the original, to achieve a measure of rise-time compensation. Called, in that field, a "constant fraction discriminator". So, each of the 32 sections had a power island with caps and a series resistor for decoupling. I just measured the dip in voltage when it switched, and was astounded to see a huge dip in voltage. Yes, there are all SORTS of parasitic inductances in the decoupling caps that makes real quantitative numbers pretty suspect.> 1A/3ns is at least 1.7V dropped across the package inductance alone. At > 3.3 or 5V supply and very nearby bypassing, I can see it being possible, > at least. >Yes, quite likely the voltage inside the chips was massively affected, if I saw that much dip at the outside.> The impedance of such a [presumed] signal is, at most, 10 ohms: > considerably less than the Zo of any reasonable structures in the vicinity > (bondwires, pins, PCB pads, even shunt resistors if not done carefully), > so the stray inductance will be quite dominant. > > Definitely a challenge to measure accurately.Oh, I assumed that any attempt to measure it had an error bar of about +/- 50% or worse. But, it told me I had FOUND the problem, and I just had to find chips that didn't have such horrible shoot through. Jon
Reply by ●February 1, 20172017-02-01
On Wednesday, February 1, 2017 at 7:09:28 AM UTC-8, John Larkin wrote:> I don't see a Tr or Tf spec in the data sheet. The 2.5 ns, in one > figure, seems to be a max for the clock input.Hmm, you're right, the waveform on page 7 is labeled CP Input ( https://www.fairchildsemi.com/datasheets/NC/NC7SV74.pdf ). Definitely nothing in that data sheet to suggest transition times in the hundreds of ps. It would be funny if it turned out that cheap carbon film resistors act like shock lines. -- john, KE5FX
