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The Propeller could beat up Chuck Noris... — Parallax Forums

The Propeller could beat up Chuck Noris...

LawsonLawson Posts: 870
edited 2012-07-28 19:50 in Propeller 1
So, turns out a Prop will run (Overclocked to 96MHz) almost perfectly off a power supply rail like the one shown below.

3v3_0u1ceram.png


A 3.3 volt average 1.2 volt peak to peak saw tooth is not normally considered a good supply rail. :innocent: The only two clues something was wrong was the serial link to the computer would drop half a line of text randomly, and the board hummed softly.

3v3_10uceram.png


This second power rail works perfectly though... A 0.8v peak to peak saw tooth is within spec for the Propeller. :cool:

Lawson

P.S. Turns out the TLV1117 regulators only work if the output capacitor has a 0.2-10 ohm equivalent series resistance. Using a 10uF ceramic capacitor turns it into a noisy saw tooth oscillator. (and it's even worse running with 0.4uF...) Easy to miss this part of the datasheet.
3v3_0u1ceram.png
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3v3_10uceram.png
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Comments

  • plainsteveplainsteve Posts: 33
    edited 2012-07-27 15:29
    Dear all,

    Lawson departed this world at 4:07 PM GMT-6. Cause of death was determined to be a roundhouse kick to the abdomen. Due to damage sustained by the body, the service will be closed-casket.

    RIP Lawson.
  • jmgjmg Posts: 15,183
    edited 2012-07-27 15:53
    Lawson wrote: »
    P.S. Turns out the TLV1117 regulators only work if the output capacitor has a 0.2-10 ohm equivalent series resistance. Using a 10uF ceramic capacitor turns it into a noisy saw tooth oscillator. (and it's even worse running with 0.4uF...) Easy to miss this part of the datasheet.

    Parts that are that fussy, should be banned.
    Too easy to have a cap go outside that "I'm OK jack" band, with age, or temperature.
    Change brands, or service the device, and you have a new lottery...
  • RickInTexasRickInTexas Posts: 124
    edited 2012-07-28 19:50
    I had a strange regulator issue with my Propeller Proto Board USB. I blew up a few SD cards and was pulling my hair out. Finally discovered that the 5v regulator was ​intermittently jumping to around 8 volts or so. Didn't have my scope handy but I suspect it was oscillating. Just replaced it with a good ol' LM7805 and went merrily on my way. Love those old things - bulletproof and I've never seen one fail in my 30 some odd years of geekdom.

    BTW, the only SD card that survived the abuse was an old 512MB Sandisk.
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