Analog IC design HowTo's

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Introduction

How to change the default simulation results and saved states directories

By default, all simulation data and results are stored in a ~/simulation directory automatically created in your home directory the first time you run a simulation with Cadence IC. Similarly, Cadence simulation states by default are saved in a ~/.artist_states hidden directoryautomatically created in your home directory.

To change these defaults, just use in your home ~/.cdsinit or ~/.cdsinit_personal files the following directives:

envSetVal("asimenv.startup" "projectDir" 'string "/path/to/your/custom/simulation/results/directory")
envSetVal("asimenv" "saveDir" 'string "/path/to/your/custom/simulation/states/directory")


You can also issue these statements at the CIW command prompt.


See also

http://www.cadence.com/Community/forums/p/17009/1179512.aspx

How to disable the annoying 'beep' sound

Solo pe rla sessione corrente:

CIW ⇒ Options ⇒ User Preferences…

poi nel Command Controls tab c'e' la Beep Volume section

Altrimenti si customizza l'environment editanto il .cdsinit

How to evaluate the power consumption

A detailed Wiki page about this topic has been created, please refer to Power consumption evaluation in Cadence.

How to use SPICE transistor models

How to define the default circuit simulator for ADE

To set the default simulator, e.g. as Spectre, enter the following environment variable in your .cdsenv or .cdsinit file. Syntax to set the default simulator in the .cdsenv

asimenv.startup simulator string "spectre"

Syntax to set the default simualtor in the .cdsinit

envSetVal("asimenv.startup" "simulator" 'string "spectre")

How to set the default models path for Spectre

Syntax to set the default model path in the .cdsenv

spectre.envOpts modelPath string "<pathTo>/myModelFile;section"

Syntax to set the default model path in the .cdsinit

envSetVal("spectre.envOpts" "modelPath" 'string "<pathTo>/myModelFile;section")

Creating a parameterized cell

e.g. creare un ideal OPAMP with a vcvs

pPar("gain")

CIW ⇒ Tools ⇒ CDF ⇒ Edit…

see also here

How to save DC Operating Points’ Parameters of a MOSFET

save M0:oppoints

Other web tutorials can be found here and here

How to evaluate rise time, delays etc.

riseTime(.....)
delay(......)

Example: Time-over-Threshold

How to make nice looking plots from Cadence

Printing the schematic

How to draw diagonal wires

This is a very useful trick to make your schematics more readable. Diagonal connections are used to draw cross-coupled transistors as in latches and flip-flops.

Press W to begin wiring, then press the F3 key. The Add Wire window will appear.

Change the Draw Mode from the default of “route” to something that allows diagonal or any angle wires.

You can also specify a 45 degree fixed angle with the relative Lock Angle option.

But you can also change between different Draw Modes simply by clicking on the mouse whell or the central mouse button!

See also

http://www.cadence.com/Community/forums/p/16772/1178636.aspx

Performing simulations with HSPICE

Se e' installato

see also here

How to evaluate the total impedance at a node

A detailed Wiki page about this topic has been created, please refer to Node impedance simulation.

How to evaluate the total input/output capacitance of a stage

In ingresso tipicamente e' quella vista sul gate of the input transistor

OP("/M0","cgg")

How to measure the OPAMP slew-rate

Si applica la definizione, mando in ingresso un voltage step e misuro

SR = max{d vout / dt }

ymax(deriv(VT("/out")))

How to choose the proper number of fingers

in potenze di 2, as Manuel dixit?

Create a custom library of ideal building blocks

cd ~/cadence
mkdir ideal_blocks
cd ideal_blocks
mkdir idealLib

poi create a cds.lib with the following directives:

INCLUDE $IC_DIR/tools/dfII/local/cds.lib
DEFINE idealLib $HOME/cadence/ideal_blocks/idealLib

poi lanciare virtuoso normalmente



Last update: Luca Pacher - Apr 23, 2013