In article <4aps73$sgd@hecate.umd.edu> LEFRAK-B-25@ writes:
>From: LEFRAK-B-25@
>Subject: Simple Crystal and Clock Qustions
>Date: 14 Dec 1995 18:59:47 GMT
>I am trying to use a National Semiconductor ADC1038 A/D converter. I want to
>attach an external clock to the Cclk input. My question is how do I hook up a
>simple crystal to this input. If this is trivial please forgive me, I am just a
>hobbyist...Below is my plan is it right, kinda right or WRONG...
>I got a CY3.57Mhz crystal. I will take two 15pf caps and place them between
>ground and each lead of the cystal. I will also place a 1Meg resistor between
>each lead of crystal.
>Now I take one side of the crystal and put it into a CMOS inverter. I take the
>output of this inverter and tie it together with the other side of the crystal
>and then put both through another inverter.
>I think I can then take the output of the second inverter and put it into the
>Cclk input.
>Any help would be greatly appreciated...
>Joe
>jkemp@bss1.umd.edu
14 MHz clock:
Aa you pointed out correctly, a crystal must be used with some active elements
to function as an oscillator; a complete schematic:
|\ |\ _ _
----| >o----------| >o----> out _| |_| |_ 3.57MHz
| |/ | |/
| ___ |
|----|___|----|
| 1M |
| | |
| _ | |1K5
| | | |
|----|| ||----|
| |_| |
| crystal |
--- ---
--- 33pF --- 18pF
| |
___ ___
/// ///
The 1K5 resistor limits the power dissipated in the crystal.
So your plan was (almost completely) correct.
Success,
Richard
Richard Rasker
Calslaan 54-11
7522 MG Enschede
Date: Sun, 17 Dec 1995 22:21:49 UNDEFINED
Original Subject: Re: Simple Crystal and Clock Qustions