Chip like LTC1799

Was it too hard to look up the linear website ? Special functions, Silicon Oscillators. They have a bunch of these parts.

Rene

TinyLogic schmitt trigger.

John

John Larkin wrote in news: snipped-for-privacy@4ax.com:

Thanks John and Rene for those two rather flippant replies.

I have been down the Schmitt road but found that for any variable resistor / fixed cap combination the frequency was not selectable.

I was asking for other manufactures of similar chips to the LTC one. If you knew off the tops of your heads that would be quite help full, but I can of course do my own research.

DaveC

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On 19 Feb 2005 06:15:45 -0600, DaveC wroth:

I saw those earlier replies and calling them "flippant" shows a remarkably high degree of restraint on your part. 8-)

Sometimes I wonder if anyone ever reads more than 5 or 6 percent of the words in a post before replying.

The little LTC1799 is, AFAIK, the only part that does what it does. It does it very well too, I might add. I can only surmise that you have a good reason for wanting an alternate part. Perhaps the PHB you work for has mandated that only second-sourced parts can be used in any design.

Single-sourced parts can sometimes be a pain, but it's a pain you have to learn to live with when you are designing on the "bleeding edge".

Jim

Why flippant? A cmos schmitt will oscillate with a single resistor, and the resistor sets the frequency. It might be useful if you don't need high frequency accuracy, it's multi-sourced, and very cheap.

Oh, don't be idea-phobic.

What's bleeding-edge about a mediocre-accuracy oscillator?

John

Sorry John, was having one of those days.

I did try a schmitt res/cap did not get very good results. I'm clocking a DAC & ADC so need mark/space within 40-60% and frequency between 20kHz &

I dont have a scope where I am, but the ADC conversions became error riden. When I get back to school in a week I can use a scope so will further investigate the schmitt option.

I need inverters for this circuit any way so the hex chip is not wasted on the board.

DaveC

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John Popelish wrote in news:4217F489.906C4CA1 @rica.net:

Yes it must hold, The frequency is controlled by the user. It's for a guitar pedal. A foot controller is used to adjust the frequency at any time. If the 40-60% mark/space is lost then you get really awful pops as the ADC drops samples.

DaveC

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For 20kHz-800kHz maybe you could use an 8-pin PIC. Just configure it to run RC oscillator mode with Fosc/4 output. You don't even need a program. 50% duty cycle is guaranteed. ;-)

Best regards, Spehro Pefhany

DaveC wrote: (snip)

Does this mean that any frequency between 20 kHz and 800 kHz will do if the symmetry stays between 40-60%, or must that symmetry hold while the frequency is adjusted, continuously between these limits?

Then I think you could rig up the VCO in a CD4046 or HC4046 PLL to do this. 40 to 1 frequency is a bit large, but if you don't need very precise limits, unit t0 unit, I think it would work.

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How about:

A CD4060 / HC4060

IIRC the oscillator part of the LT1054 runs at about 30KHz. You can combine the oscillator with another useful circuit.

A TICPAL22V10Z could make the oscillator and divide by two with some extra sections to make other glue logic.

I read in sci.electronics.design that John Larkin wrote (in ) about 'Chip like LTC1799', on Sat, 19 Feb 2005:

It operates at around 30 THz? (;-)

Development without a scope can be rather hard, especially when the parts don't behave as expected. To get a 50% dutycycle, a Flipflop as divide-by-two could be helpful. But only if the slopes are sufficiently fast.

Rene