insane flipflop measurements

Neat, the data sheet says Tr = 2.5 ns.

Photo of test setup?

-- john, KE5FX

Nice measurements :-)

We use it also, but never bothered to do any qualification

Isn't it the rise time that is beyond amazing?

Cheers

Klaus

Am 31.01.2017 um 05:08 schrieb John Larkin:

Looks interesting!

This is what I got from a pair of SN74LVC1G04DCKR, 50 Ohm source and load terminated, running on 6V, still legal. I wanted acceptable 3V3 CMOS levels @ 50R input. It varies somewhat from batch to batch.

< > and left/right

Scope rise time is 145 ps.

cheers, Gerhard

How much load were you driving?

--
Boris

If believable. The rise time makes no sense.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Just 500 ohms, a series resistor into a 50 ohm coax.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

From the sticky-note, the risetime is from the clock; the falltime from Clear. Does the fall-time change if the device is configured to toggle? {WAG not what you want in your application}

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.)

I was using the TI SN74LVC1Gxxx family. I then tried the NXP 74AUP1Gxxx family as they specified a really low "equivalent switching charge" and in fact, the shoot-through was not measurable. That required a complete redesign of the boards, though!

Jon

Here's the breadboard.

I didn't expect it to be so fast, and the carbon film resistor pickoff from Q to the scope is maybe questionable. But I tried probing Q with an HP54006A resistive probe, rated 6 GHz, and the risetime is still around 200 ps. At that point, my breadboard starts to matter. That US8 adapter is something I threw onto another PCB layout just for fun, not intended for this sort of speed. US8s are horrible little packages.

This flop, pulsed at clock and clear, cheerfully makes a reasonably square 700 ps pulse.

I would have expected the fall (nfet) to be faster than the rise (pfet) but semiconductors make no sense.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

That's pretty clean.

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.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

It looks faster on the falling edge if I only use the clock. In toggle mode, rise is maybe 150ish, fall maybe 250. There is some overshoot and ringing, and that fools the scope rise/fall measurements, but it's plenty fast.

I'll be using clock and clear to make my pulses.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Am 31.01.2017 um 23:31 schrieb John Larkin:

Mouser says it is obsolete. Maybe reels of 6000 still available.

Sigh, Gerhard

Am 31.01.2017 um 23:57 schrieb Gerhard Hoffmann:

No, the -usg version is still available. They are waiting for the 6K devices.

What's the best edge-time you've seen from these TinyLogic parts? Got a plot handy? Better than an LVDS driver?

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).

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.

Clifford Heath

Hrm, curious how you measured that?

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.

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.

(I wonder if anyone makes a Rogowski coil small enough to slip around an SOIC pin...)

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: http://seventransistorlabs.com

Yikes, don't scare me like that!

There are other, drop-in parts, but the Onsemi version is the best.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

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.

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.

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.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Interesting, thanks.

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.

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.