The Designer's Guide Community
Forum
Welcome, Guest. Please Login or Register. Please follow the Forum guidelines.
Oct 24th, 2020, 2:21am
Pages: 1
Send Topic Print
Question regarding track and hold model (Read 3321 times)
gmande
New Member
*
Offline



Posts: 2

Question regarding track and hold model
May 03rd, 2004, 2:01pm
 
Hello Experts,

I have a question regarding track and hold model explained in "Hidden State in SpectreRF" document. Please refer to Section 4, Figure 1 and Listing 2. In listing 2, the veilogA model th contains an internal node hold. V(hold) has been used inside the code. But I am not able to understand where and how the V(hold) value is getting eavaluated.

Please let me know if you need more information.

Thanks and Regards,
Geeta...
Back to top
 
 
View Profile   IP Logged
Andrew Beckett
Senior Fellow
******
Offline

Life, don't talk to
me about Life...

Posts: 1736
Bracknell, UK
Re: Question regarding track and hold model
Reply #1 - May 3rd, 2004, 2:45pm
 
Isn't it fairly clear:

Code:
// Implement switch with effective series resistence of 1 Ohm
if (($abstime > tstop  aperture) && ($abstime <= tstop))
  I(hold) <+ V(hold)  V(Pin, Nin);
else
  I(hold) <+ 1.0e12 * V(hold);
// Implement capacitor with an effective capacitance of tc
I(hold) <+ tc * ddt(V(hold));
// Buffer output
V(Pout, Nout) <+ V(hold);
 



The first bit is a switch, which is either a 1 ohm series resistor,
or a leakage resistance of 1 teraohm to ground.
The second is the equation for a capacitor.
And finally V(hold) is used.

With Verilog-A you can write the relationship between currents and voltages - you don't always have to formulate the equation so that the voltage is assigned to.

For example, a resistor can be defined as:

Code:
I(plus,minus) <+ V(plus,minus)/R; 



just as well as:

Code:
V(plus,minus) <+ I(plus,minus)*R; 



both forms are effectively equivalent.

So do you understand now? If not, can you elaborate on what it is you don't understand?

Regards,

Andrew.
Back to top
 
 
View Profile WWW   IP Logged
gmande
New Member
*
Offline



Posts: 2

Re: Question regarding track and hold model
Reply #2 - May 4th, 2004, 1:03pm
 
Hello Andrew,

Thank you so much.

Best Regards,
Geeta...
Back to top
 
 
View Profile   IP Logged
Eugene
Senior Member
****
Offline



Posts: 262

Re: Question regarding track and hold model
Reply #3 - May 4th, 2004, 7:34pm
 
You can also use a resettable integrator that integrates zero. Set the integrate indentically to zero. Insert the input you want to track and hold into the integrator's initial condition. When the integrator's assert input is nonzero, the integrator tracks the time varying initial condition. When the assert input drops to zero, the integrator holds the initial condition. I have used this successfully with SpectreRF.
Back to top
 
 
View Profile   IP Logged
Pages: 1
Send Topic Print
Copyright 2002-2020 Designer’s Guide Consulting, Inc. Designer’s Guide® is a registered trademark of Designer’s Guide Consulting, Inc. All rights reserved. Send comments or questions to editor@designers-guide.org. Consider submitting a paper or model.