Archive for the ‘Cadence’ Category

Cadence 6.14 Virtual Machine

Thursday, October 15th, 2015

Research Links

Cadence 5.11 Virtual Machine

Wednesday, October 14th, 2015

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Stray Capacitance in MIM XFAB XH018 Capacitors

Monday, October 5th, 2015

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Cadence Error LX-2063 Technology Library cdsDefTechLib contains no constraint groups

Monday, October 5th, 2015

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When I have a schematic open and click on  Launch > Layout XL the following error pops up.






I found cdsDefTechLib in the library manager as shown below under CadenceLibs.  I need to know what to do with that!  I'm blank at the moment as I often am when using Cadence software.   As blank as when you click on cdsDefTechLib in my current state of setup as shown in the library manager there is nothing listed when I click on cdsDefTechLib


Arun created a test library and when a dialog box came up he _____ with the existing technology library  TECH_XH018.  As you see below the "test" library came up under the XFABLibs tree in the library manager


Right clicking on "test" and clicking on properties gives:


As compared with right clicking on PowerSupply which gives the following dialog box where you see that the techLibName is the generic cdsDefTechLib that is under CadenceLibs and has nothing in it.


So now I have to either find a way to take the existing design library and associate with the existing technology library TECH_XH018  or  make a new library that is associated and copy the files in.

Varying Parameters during a Cadence Transient Analysis – Dynamic Parameters and Feeding Final Conditions into Initial Conditions

Monday, September 14th, 2015

Research Links

Click on the option button to get to the windows where you specify the file to read the circuit initial conditions.


The state file tab has the spectre.fc file specified which is the file that stores the final conditions after a simulation.

Final-And-Initial-Condition-Files      ReadIC

When you go to the "Algorithm" tab you can specify a file with your circuit initial conditions.  For my transient analysis optimizations of charge pumps I wanted to pick up from where the circuit analysis left off with a component value changed.  Thus I feed the spectre.fc file into the readic file. 

Cadence Vector Files

Friday, September 11th, 2015

This is mostly a place holder for later when I need to know about Cadence vector files. 

Research Links

Cadence: VCO Design Using SpectreRF

Tuesday, September 1st, 2015

I was looking for a way I could plot the output frequency of a ring oscillator versus an input tuning voltage.   I did not find anything easy and fast in the literature but I think PSS is the key for the more formal methods.  PSS = Periodic Steady State.  I will look at this later most likely for other applications.  To see what I did do for a useful plot of F versus Vtuning see below.

Research Links





The current consumption of the ring oscillator is more or less proportional to frequency and thus can be used as a plot of frequency versus voltage.  The tuning voltage goes into a gate of an mosfet.  You can see most of the tuning action occurs just below the Vt of that mosfet since the fet is being used with such low currents.

Data Points

  • 500 kHz @ 69 nAmp
  • 200 kHz @ 31 nAmp

Assuming current consumption directly proportional to frequency gives 0.000014 nAmp / Hertz.  This checks out.


Creating a Parameterized Cell in Cadence

Monday, August 31st, 2015

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1 nanoamp Current Source with No Resistors Using Self Cascode MOSFET

Thursday, August 13th, 2015

Note the 500M Ohm resistor is only to test the current reference.  It would be replaced by your application circuit.

Research Links

 Archive:  Current-Source.7z     Program = LTSPICE

Extract into directory.  Includes the required MOSFET library file.



Output Current


Supply Current

Ultra Low Current Band Gap References Using NanoAmps of Current with Good MonteCarlo Results

Tuesday, August 11th, 2015

If you need a voltage reference when doing energy harvesting it is very helpful have a band gap reference that uses very little current.  This topology uses “Self Cascode Mosfet”  abreviated as SCM.  The LTSPICE design uses 4.5 nano Amperes and outputs a 0.6 Volt reference voltage.

Research Links



   Archive: Voltage-Reference.7z      Program = LTSPICE

Extract into directory.  Includes the required MOSFET library file.


LTSPICE Analysis

Vref versus Temperature


Voltage reference current consumption versus temperature

Monte Carlo Analysis with Cadence

  •  Note how tight the voltage control is
  • Current usage = 1 nAmpere

MC_Voltage-Reference_V09 Schem_Voltage-Reference_V09