[time-nuts] Bye-Bye Crystals

Bob Camp kb8tq at n1k.org
Tue Mar 14 08:04:40 EDT 2017


Hi

> 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 need
>> 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 likely
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 and 
not super tight tolerance … you go with the crystal. 

Bob

> 
> Is your background digital or analog?  Do you want a sine wave or a clock?
> 
> 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 caps 
> 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 look 
> 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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