Jim Thompson wrote:

On Mon, 06 Aug 2007 13:58:42 -0700, Joerg
wrote:


Jim Thompson wrote:


On Mon, 06 Aug 2007 20:11:14 GMT, Joerg
wrote:



Jonathan Kirwan wrote:



On Mon, 06 Aug 2007 19:35:40 GMT, Joerg
wrote:




Jim Thompson wrote:




Joerg, Why don't you try the attached version?


Ok, just did: It chokes, creating humongous bursts of spikes on VCC.
There is no longer a normal oscillation :-(


Can you try it more like this?

||
,---/\/\----+---||------,
| 1M | || 10n |
| | |
| \ |
| / 1M |
| \ |
| | |
| |\ | |\ |
+---| o----+----| o---'
| |/ |/
|
---
--- 10p
|
gnd


Thanks, Jon, done that before and it did not help the cross current at all.


Make the left-most 1M into 10K.


Done that, too. Then it oscillateth no more.



Where's the 10pF coming from?


Don't know but I've tried several caps.



Or, naughty question of the week, Why are you using 4000 series CMOS
in the 21st Century ?:-)


Because it's cheap and does away with the need for regulated VCC. Plus
the functionality of this stuff is so great that some of it was even
ported into other families. For example 74HC4060. But there you can't
have a 3V-18V VCC range anymore.

This design, however, is one that's slated for a port into uC land. The
oscillator in those 4060 devices appears not to be one of the smarter
design in the CD series. Got to think hard about that porting because I
absolutely will not employ any LDOs in there. No way. Guess I'll be
rolling my own. Again.


Are you making a custom uC? Or just using spare inverters/gates for
your clock?


The uC would run off its on-chip clock, comes factory calibrated. But I
would need two independent uC because there must be an "Are you still
alive?" check as usually found on mission-critical aircraft systems.

--
Regards, Joerg

http://www.analogconsultants.com