Stats

  • Locked Locked
  • Replies 7
  • Subscribers 126
  • Views 21411
  • 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

Schematic editor bus naming and connections questions.

mhkvy4

I have 2 questions about instantiating multiple instances, the multiplier parameter and bus naming conventions in the Schematic editor. If I want to connect 4 MOSFETs( in parallel), in series, with another set of parallel MOSFETs like in figure A, do I do it using figure B or figure C. (I think it is figure B). If I do instantiate four MOSFETs like in figure 3, for both the top and bottom set, and if I make the connecting net a bus of width 4 bits then I think I get figure D.

1)So if I have this right figure A and B are the same, D and C are the same. Is this wrong? 

2) if i want to declare an array of say 128 identical series resistors, how do I go about it? 

Do I have to make the nets on either side a bus of 128 bits and instantiate resistors with R<127:0>? How do I go about declaring an array of identical parallel resistors? I am guessing for a parallel array I don't make the nets on either side of the R<127:0> into 128 bit buses. 

Parents
  • Marc Heise

    Hi,

    the m parameter is a model parameter, so there might be difference between having four separate devices and one device multiplied by 4 in the model card. Think along shared S/D areas and their cap values.  C and D are identical, yes.

    For series resistor arrays there is the s-parameter which we support. I don't know if your PDK supports this.  As  workaround you can  use the iterated instance method for series connection as well by defining kind of a loop:

    Expression  on the input net:  IN, internal<127:1>

    Device: RES<128:1>

    Expression on the output net: internal<127:1>, OUT

    IN - RES<128> - internal<127> - RES<127> .........RES<1> -  OUT

    Very useful for any kind of chains. (inverter delay line or ringos), just make sure your layout people are aware of that technique. ;)

    If you want them to be parallel, just connect the array to only one net on each side, if you declare a bus, the devices will be separated.

    Kind regards,

    MMarc

  • mhkvy4
    in reply to Marc Heise

    Thanks for the reply Marc.

    Just wanted to make sure that I am understanding you right. If I wanted to declare an array of 128 parallel resistors then I should declare it as  IN - RES <128:1> -OUT 

    where IN and OUT are the net names on either side. 

Reply
  • mhkvy4
    in reply to Marc Heise

    Thanks for the reply Marc.

    Just wanted to make sure that I am understanding you right. If I wanted to declare an array of 128 parallel resistors then I should declare it as  IN - RES <128:1> -OUT 

    where IN and OUT are the net names on either side. 

Children
  • Andrew Beckett
    in reply to mhkvy4

    For a parallel resistor, better to use m if you can because it's better for the simulator, but if you did want to do it, then it would be like the bottom resistor in the picture below. The top resistor shows a series-connected resistor chain.

  • mhkvy4
    in reply to Andrew Beckett

    Thanks a lot Andrew. This was a big help. 

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.