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100 Mhz sq wave w/ >5 pSec jitter?

Discussion in 'Electronic Design' started by [email protected], Nov 16, 2004.

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  1. Guest

    I have a request to measure the edge-to-edge jitter from some F100314
    diff ECL line drivers. The customer wants it done with 100 MHz square
    waves, and the jitter spec is > +/- 5 pSec. Does that mean I need a sq
    wave with better than that jitter? Can I get one?
    Or: could I trigger off the sq wave source while inputting it into the
    line driver, then look at the output of the driver on the scope and
    measure the time from trigger to output edge rising and get the jitter
    of that time?
  2. John Larkin

    John Larkin Guest

    Yup. A medium-good 100 MHz ECL xtal osc will have maybe 1 ps RMS
    jitter. Vectrons are good.
    Do that too. The problem there is being sure that the edge you're
    observing is the same one that caused the trigger; if not, you're back
    to depending on the oscillator's cycle-to-cycle jitter being low. Most
    sampling scopes have a 40-70 ns trigger delay, several clock cycles. I
    guess you just prowl the edges for the one with the least jitter!

    You can also measure jitter with and without the chip in the path, and
    deconvolve the device jitter. That takes out both the oscillator and
    the scope jitter.

    What kind of scope do you have? Samplers run roughly 1-3 ps RMS jitter
    all by themselves, when they're in a good mood.

    I sure hope you're talking 5 ps RMS, and not peak-to-peak.

  3. mike

    mike Guest

    Sometimes people requesting measurements don't fully grasp what they're
    asking and don't have any idea what they're gonna do with the data when
    they get it. I'm gonna go way out on a limb and state that measuring
    5pS in a circuit environment other than the actual application is

    Look at the slew rate of the input and figger out how much noise, power
    supply rejection, reflection influence etc. it's gonna take to swamp
    your measurement. Even if you make the perfect circuit, how will that
    translate to the actual environment?

    Having said that...Can you make a ring oscillator and look at the FM
    with a spectrum analyzer?

    Return address is VALID.
    500MHz Tek DSOscilloscope TDS540 $2200
    Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
    Bunch of stuff For Sale and Wanted at the link below.
  4. Guest

    Thanks for the response.
    Oooh, good idea on the XTAL osc, I'll probably do that.
    I've got a TDS5104 ( I think its a 4) with the jitter package
    installed, but I'm stuck on a source.
    What Harris suggested is a splitter/delay method, trigger off the
    undelayed, display and find the delayed trigger edge and meas the
    jitter of the time till the next edge. But right now I'm measuring
    "period jitter" using the option in the scope. I'm getting ~50 pSec
    using an old HP pulse gen.
  5. Guest

    An outside company came to us and asked "can you verify that the
    edge-to-edge jitter of these ECL F100314 parts is < 5 pSec? ". They
    sent a drawing of a suggested setup: splitter/delay line. From what
    I've found searching, it's a recommended method, but I'm not sure of
    the impact of the source on the reading. I know jitter is related to
    phase noise by integrating and there's a nice spreadsheet to calculate
    it out there somewhere (Wenchel website?), I could do some thing FM,
    but... of course they don't want to spend any money or time, but want
    it done fast, like tommorow, and cheap, so don't waste time figuring
    anything out, hook somethings up, push a button on the scope and write
    down the right answer!.
  6. mike

    mike Guest


    don't waste time figuring
    Where can I get a job like that. I'm there in a New York Minute ;-)

  7. Fred Bloggs

    Fred Bloggs Guest

    You will never do it:
  8. John Larkin

    John Larkin Guest

    I do measurements like that all the time. My 11801A scope has
    trigger-to-vertical jitter of about 1.5 ps RMS, so it can make useful
    device jitter measurements to about 1 ps. (Just got a CSA803C off
    ebay, lower jitter still, but haven't fired it up yet.)

    The guy in the article chose not to mention equivalent-time sampling
    scopes; the newer ones have jitters way below 1 ps.

  9. Rich Grise

    Rich Grise Guest

    Depends what kind of money you want to make. I've got a guy right now
    who will let you do that.

    For seven-fifty an hour. ;-)

  10. Guest

    You guys are scaring me.
  11. Guest

    Thanks for the article. I'll add it to my growing collection. At least
    I'm learning alot. My scope is a TSD5104 with 8 pSec trigger jitter.
  12. Guest

    Congrats on the new CSA !! How much was it? I'm using a TDS5104. They
    say it ha ~8pSec trigger jitter. With the best source I have, I'm
    getting 50-60 pSec jitter.
  13. John Larkin

    John Larkin Guest

    About $1200. The older boxes, 11801 or 11802's, go for a few hundred.
    It's the sampling heads that are expensive; $500 for an SD14 dual
    probe (3 ghz), $800 maybe for an SD22 (12 ghz dual-channel), kilobucks
    for an SD24 (20 GHz TDR). Still cheap compared to the new stuff!

    Your cycle-cycle jitter is probably the pulse generator. Even a cheap
    20 MHz TTL xtal osc can do a lot better than 50 ps. There are lots of
    cheapish ecl xtal oscillators that will guarantee 1 ps RMS.

  14. The jitter is measured as close sideband noise. Just integrate the
    spectrum found from 10 to 1MHz beside the carrier on either or both sides.

  15. Guest

    Thanks to all for chiming in. I really appreciate the info, you can
    tell I'm out of my realm here.
    Here's what I'm getting: Using a TDS5104, trigger jitter ~ 8pSec, to
    measure the jitter of just the source, a Tektronix AWG2021, I get ~ 45
    pSec. Measuring one of the outputs of the ECL part, F100314, with the
    unused outputs terminated in 50 ohms, I get ~ 30 pSec. Why less, and
    not more?
    Digikey carries an Epson 106 MHz XTAL osc, 3 pSec RMS jitter. I
    ordered a couple. I'll use one for a source and post what I get.
    Stay tuned...
  16. mike

    mike Guest

    What are you using for a test breadboard?
    If you think of the the input slew rate as millivolts of noise per
    picosecond of jitter, you quickly determine that you can't have any...

    Return address is VALID.
    500MHz Tek DSOscilloscope TDS540 $2200
    Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
    Bunch of stuff For Sale and Wanted at the link below.
  17. sdy

    sdy Guest

    I have a very nice board I made from copper clad. ( The device the 5
    ECL line drivers, F100314) One set of inputs is tied to device's
    internal refernce voltage, the other inputs are connected to SMAs by
    50 ohm coax, shields soldered to copper PCB. Outputs are connected
    likewise, un-used ones terminate in 50 ohm sma loads. The device is in
    a good socket and power suppies bypassed at the socket.I took care
    knowing I needed fast, highh freq signals. At 30 MHz, theres no
    ringing at all and rising/falling edges are very nice.
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