Stats

  • Locked Locked
  • Replies 2
  • Subscribers 63
  • Views 15145
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

One testbench for PSS and Transient Simulation with different stimuli.

Thomas T

Hi,

 I am trying to setup an all-purpose testbench for some amplifier circuits I need on a regular basis that can be used for all the simulations I normaly use: DC, AC, TRAN and PSS.

 The problem I have stems from the fact, that I need to test my circuit in a pulsed operating mode in the transient simulation: the circuit has a node called "powerdown" which is driven by a VPWL voltage source. This activates and deactivates the circuit for a certain amount of time, allowing me to observe the transient behaviour of the circuit with regards to settling time etc. in a pulsed operating mode.

For my PSS simulations, where I want to establish the 1dB-compression point for example, the powerdown-node needs to be set to a defined voltage, in my case 0 volt (or connected to ground) in order to avoid the frequency components of the powerdown source. Is there a way, to setup both in one testbench ? For DC-simulations, I can just set the DC value of the vwpl source to 0 and everything works as expected. I haven't found a way to do the same for PSS simulations which leads to me always having to make a copy of the testbench where I then statically connect the powerdown node to ground. This has lead to mistakes in the past and I would prefer a single testbench that just works and can be reused.

 Thanks !

Parents

  • Shawn,

    Actually that won't work. The tstab is additional time added on to Tonset (the onset of periodicity). It will simulate for as long as needed for the sources to be periodic, and then the tstab. So with a tstab of 1u, if you have a source with a delay of 1m, it will simulate 1m+1u for the initial transient.

    Thomas - a couple of approaches I'd suggest:

    1. Put a design variable on the "stretch" parameter of the vsource (a PWL parameter). This allows you to scale the time values in the PWL. So for example, I have this netlist (easier to show a netlist than a picture of the parameters):

      parameters high=0 timefactor=1e-15

      v1 (n1 0) vsource type=pwl wave=[0 0 1u 0 1.01u high 2u high 2.01u 0 3u 0 3.01 high] stretch=timefactor
      vclk (n2 0) vsource type=sine freq=500M ampl=1

      pss pss fund=500M

      By setting high=0 and timefactor=1e-15 it scales all the times to be tiny, and the amplitude variation to be 0. You can't set timefactor to 0 unfortunately. If you set high to be your desired peak value and timefactor=1, the PWL will behave as you want it for the tran analysis.
    2. Add two sources in your testbench - in parallel. One that you'll use for tran and one for PSS. Then create two config views for the same schematic, and use the instance binding "bind to open" for one of the sources in one config, and for the other source in the other config. Then you simulate using the config views. Bind to open means that the instance will be omitted from the netlist. One schematic to maintain, and two very simple configs. You can use the same approach to switch in and out other testbench components.

    Regards,

    Andrew.

Reply

  • Shawn,

    Actually that won't work. The tstab is additional time added on to Tonset (the onset of periodicity). It will simulate for as long as needed for the sources to be periodic, and then the tstab. So with a tstab of 1u, if you have a source with a delay of 1m, it will simulate 1m+1u for the initial transient.

    Thomas - a couple of approaches I'd suggest:

    1. Put a design variable on the "stretch" parameter of the vsource (a PWL parameter). This allows you to scale the time values in the PWL. So for example, I have this netlist (easier to show a netlist than a picture of the parameters):

      parameters high=0 timefactor=1e-15

      v1 (n1 0) vsource type=pwl wave=[0 0 1u 0 1.01u high 2u high 2.01u 0 3u 0 3.01 high] stretch=timefactor
      vclk (n2 0) vsource type=sine freq=500M ampl=1

      pss pss fund=500M

      By setting high=0 and timefactor=1e-15 it scales all the times to be tiny, and the amplitude variation to be 0. You can't set timefactor to 0 unfortunately. If you set high to be your desired peak value and timefactor=1, the PWL will behave as you want it for the tran analysis.
    2. Add two sources in your testbench - in parallel. One that you'll use for tran and one for PSS. Then create two config views for the same schematic, and use the instance binding "bind to open" for one of the sources in one config, and for the other source in the other config. Then you simulate using the config views. Bind to open means that the instance will be omitted from the netlist. One schematic to maintain, and two very simple configs. You can use the same approach to switch in and out other testbench components.

    Regards,

    Andrew.

Children
No Data

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.