Pulse Stretcher

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

How accurate?

Wow, Fairchild has the 4538 as obsolete. bummer. I've used the 4040 counter in the past to generate long pulse times. Fed by a slow running 555. Just what you wanted to hear ;)

Cheers

Optical?

Bwahahahahaha!

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Mr.CRC
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Sloppy. I can tune a fairly accurate master oscillator with a pot.

I'm leery of RC due to leakage. ...Jim Thompson

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| 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     |

      Remember: Once you go over the hill, you pick up speed

A low-pin-count microcontroller makes a dandy delay element, depending on the frequency of the master clock. If you have other slow functions that can be dumped into it also, it can be cost/space effective.

Why not the 4541? Has oscillator and divider chain, plus a *256 calibrate mode for setting long timers.

Grant.

Use an up/down counter (7490?), count up fast during the pulse, count down slow afterward.

Or use a micro to do the same thing (if you're not making custom silicon). Is a SOT-23 package too big?

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http://www.wescottdesign.com

You didn't say much about your environment. If you are building a board rather than a chip, long delays are simple in software.

Assuming you want to use a counter...

Make a counter that is big enough. Load it with a magic number. After N cycles, it will overflow. Add glue around the edges to make it do what you want.

Suppose you have an active low load signal. Wire that to the pulse-out FF. Set the pulse-out with the pulse-in. Use the carry-out the top to reset the pulse-out FF. It will sit there reloading itself until you poke it again.

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These are my opinions, not necessarily my employer's.  I hate spam.

Maybe one of those single ripple counter ICs available (now) or umpteen years?

So, just a monostable; for this, a dual op amp, one half configured as integrator (1M input resistor, 1uF feedback capacitor). With 1V input, it slews one volt per second. With

0.1V input, it slews one volt in ten seconds.

Start by shorting the integrator capacitor. Then, the second op amp, wired as comparator to 1V, will trip in ten seconds.

n ____|____ / \ | . . . | +-+-------+-+ CLK>---------------|> | +----+ | DIV n | IN>------|S Q|-+--|E TC|-+ | | | +-----------+ | +-|R | | | | +----+ +--->OUT | +-------------------------+

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JF

This guy graduated from MIT, and calls himself an engineer, and doesn't understand counters? He totally panics and freezes up when he hears the "D" word.

I'd help him, as I'd help any digital newbie, if he wasn't such a creep.

John

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

I believe that one of the new Linear Tech parts in the 'timerblox' family will do this. The one shot version goes 1uS to 34 Seconds with one resistor change. Your choice of triggering options.

Oppie

You mean "Democrat"? Bwahahahaha!

50+ years doing analog. I usually hand my digital work off to an associate, but this is a G-job.

I'm looking for low device count and elegant.

I rather be a creep than a bipolar bastard ;-) ...Jim Thompson

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| 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     |

      Remember: Once you go over the hill, you pick up speed

Thanks, John F !!!

I knew it was simple. I was just having a brain freeze :-) ...Jim Thompson

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| 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     |

      Remember: Once you go over the hill, you pick up speed

"Jim Thompson" schreef in bericht news: snipped-for-privacy@4ax.com...

Well, the basic idea is to use the pulse to be streched to set a flipflop (asynchronously) and to start the counter. When the counter overflows it resets the flipflop and stops the counting until the next pulse appears.

petrus bitbyter

74HC123 goes quite nicely to the 10 second range with RC's. 555 derivatives do too too and is retriggerable if you hang a PNP outside (see datasheet for example).

If you want to use a counter, try a 74HC4060.

Tim.

JT says "I'm leery of RC due to leakage" which puts him as out of touch with analog design as he's out of touch with digital. Hmmmm.... what's left?

No, he doesn't understand counters.

He'd better use a spring timer.

John

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