Hi all
I used a cd4046 to to produce a square and triangle wave
It has a constant current on the capacitor pin so producing also a triangular wave form on that pin . The circuit works well at pspice
but in my board I get different results as pictures below
please help me

 

You don't show a schematic of the constant-current source and my crystal ball is out-of-order, so how can we tell what's wrong?

 

Hi thanks for your response . I read on a web site that it has some kind of constant current on capacitor pins and it is shown on spice simulation but the problem is that on board I did not get same result .what is the reason ?

 

We can't see your board from here!

 

my board:

 

How does the modern generation do "electronics" without a schematic ?

 

How does the modern generation do "electronics" without a schematic ?

I sent pspice schematic .

 

Friends please reply me if you do not receive my pictures .

 

Now I have to refresh how the VCO in the 4046 is constructed. A example of the data sheet can be Texas Instruments: CD4046

On page 11, there is an expanded block diagram of the VCO. It can be seen that the timing capacitors one end is connected to ground when charging with the constant current of opposite end of the capacitor, and after a half cycle time is changed to the opposite terminals of the capacitor.

So that will measure a sawtooth curve when measured at one end of the time capacitor.
http://www.ti.com/lit/an/scha002a/scha002a.pdf

 

Try connecting the resistor that presently goes to pin 12 to pin 11 instead.

 

Why do you have pin 15 connected to V+?
It should be left open or connected to ground.

 

Why do you have pin 15 connected to V+?
It should be left open or connected to ground.

it is connected to ground not v+

Now I have to refresh how the VCO in the 4046 is constructed. A example of the data sheet can be Texas Instruments: CD4046

On page 11, there is an expanded block diagram of the VCO. It can be seen that the timing capacitors one end is connected to ground when charging with the constant current of opposite end of the capacitor, and after a half cycle time is changed to the opposite terminals of the capacitor.

So that will measure a sawtooth curve when measured at one end of the time capacitor.

thanks
I read that page
you say right
but why pspice draws a triangular wave ?

 

it is connected to ground not v+

......................
but why pspice draws a triangular wave ?

Yes, I mis-traced the connection.

Kjeldgaard is correct. You will measure a sawtooth voltage from one end of the capacitor to common as the circuit shows.
What, exactly is the Pspice plot measuring?

 

Do you now have a resistor between pin 11 and ground?

 

This is a good example of why you should not DESIGN with a program, any program.

 

Yes, I mis-traced the connection.

Kjeldgaard is correct. You will measure a sawtooth voltage from one end of the capacitor to common as the circuit shows.
What, exactly is the Pspice plot measuring?

Do you now have a resistor between pin 11 and ground?

Yes , of course

This is a good example of why you should not DESIGN with a program, any program.

I think so

 

I meant at what point in the circuit is the Pspice voltage being measured?

 

Can you post a link to the Pspice model of the 4046? The spice model I downloaded doesn't work properly.

 

Can you post a link to the Pspice model of the 4046? The spice model I downloaded doesn't work properly.

Hi sorry for late response
I did not download it , it was in my library list

 

If you require to generate a triangular wave from a square wave, use an integrator.