Joerg wrote:

Chris Jones wrote:

Joerg wrote:


Chris Jones wrote:


Joerg wrote:



Chris Jones wrote:



Joerg wrote:




Hello Folks,

See the scope plot and excerpt from the ON Semi datasheet for the
CD4060. The blue trace is at the node RS/Rtc/Ctc, the yellow trace is
at pin 9 which is an output.

Why is there sag at the end of each phase? Rs is 500K and Rtc is
100K. I mean, that shouldn't be any load to write home about even for
a CD series part.



From the polarity of the step in the waveform (which must be the same
on

both ends of the capacitor for reasonable peak currents through the
capacitor), I would say that the yellow trace has to be Pin 10, not
Pin 9.


Nope, yellow is pin 9.


Are you *sure* sure ?


Not so sure anymore. Used the wrong datasheet. You are right, it is pin
10. Still puzzled why the transition is so sluggish. At 8-10V I would
have expected a lot more oomph even from a single stage inverter.



(or are you sure the pin numbers on the schematic are right?) It
doesn't make sense if Out2 jumps up in the middle of the scope display
and the
other end of the cap jumps down. Since that doesn't make sense, I think
something is wrong here.


I guess so. How embarrassing. But why is it so sluggish? Even the old
HCU04 has more zing.


Well, I don't see what you mean by sluggish - the edges are pretty crisp
on this timescale and the droop at the end of the yellow waveform can be
explained as follows:

You're looking at Out1, I think. So the blue is the input to an inverter
and the yellow is the output of the same inverter. The blue (input) is
very slowly approaching the threshold of the inverter and as the input
gets very close to the threshold, by definition, the output will also
start to approach the threshold.

Look at the other output, out2, and the droop should be gone.


I did, and it is gone. But I've not yet seen CD4000 unbuffered inverters
begin to cross conduct so far away from center. Then again I don't do
analog stuff with them at such high supplies.


The relevant measure is "how far away from the nearest supply rail", not
"how close to the centre". If it is further from the VDD rail than the
p-channel threshold, and further from the VSS rail than the n-channel
threshold then you'll get plenty of supply current.

Chris