[time-nuts] Bye-Bye Crystals
scott.j.stobbe at gmail.com
Tue Mar 14 13:16:24 EDT 2017
Not only that. Good luck finding a datasheet with *any* analog
specifications for its internal oscillator. Here are the pins for an
external crystal. The microchip PICs are nice, they give you the goldilocks
selection for drive level a little cool, a little hot, maybe just right.
On Tue, Mar 14, 2017 at 8:04 AM, Bob Camp <kb8tq at n1k.org> wrote:
> > On Mar 14, 2017, at 4:44 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
> > artgodwin at gmail.com said:
> >> I'm not after quality - I do have an application in mind but it doesn't
> >> to compete with mass production. Just wondering if it's feasible to make
> >> something crude that will resonate.
> > Are you doing this for fun or ???
> > Feasible? Sure. Cheaper? That depends.
> > The cost difference between a complete oscillator package and a simple
> > crystal is tiny. The osc is often cheaper if you include board space or
> > engineering time.
> Purchased in volume, the difference it the price of a crystal vs a
> complete XO
> is enormous. You will see at least a 10:1 cost savings on the crystal and
> more than that. Simply attaching a crystal to the internal oscillator
> inside a
> chip is nearly zero engineering cost. If your product is cost sensitive
> not super tight tolerance … you go with the crystal.
> > Is your background digital or analog? Do you want a sine wave or a
> > My background is primarily digital. If the chip you are using has 2 pins
> > setup to drive a crystal, you can probably get it to run reliably by
> > following the data sheet and/or app notes. The usual recipe is 2 tiny
> > and a big resistor. (big in resistance, not physically big)
> > An advantage of using a crystal with the on-chip amplifier that I didn't
> > mention last time is that you save the osc power if you power down that
> > corner of the chip.
> > If you want a sine wave, you are out of my comfort zone. I'd probably
> > in ham radio literature.
> > They make logic chips like a 74HCU04, U for unbuffered. One of their
> uses is
> > for making oscillators. I've never done it. Try google.
> > --
> > These are my opinions. I hate spam.
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