sroy729 / vsdOSPowerCalc

OS-power-analysis-tool

Power analysis has materialized as a principal theme in today’s world of semiconductor industries. Very Large Scaled Integrated Circuits (VLSI) are far beyond human ability because of complexity. So to analyse power in these circuits we use open source computer aided tools, plenty of tools are available but most of them are costly. I designed open source power analysis tool for the academic use which analyse power dissipation (average switching and leakage power) efficiently.

Power analysis

Power analysis of design can be reconnoitred at several levels such as system level, architectural level, logic level, circuit level and device level. Power analyser is a tool which determines how much power is utilize by a system or circuit. In this process we give circuits as input along with few operating conditions to power analyser to get report about the power.

For power analysis I simulate D flip flop using pass transistor, transmission gate, pass transistor with stacking of transistor. Simulate 2-4 line decoder using CMOS logic and TG, DVL alternatively. Simulate 2-1 MUX using pass transistor, transmission gate, MTCMOS logic. Generate netlist and input output and power(V * I) waveform for all schematic circuit.

Average or Switching Power Dissipation

The significant cause of it is switching activities that occur in circuits. Or we can say that it occur during charging and discharging of capacitance as shown in figure.

Where CL is loading capacitor, VDD is power supply, α is activity factor and f is clock frequency. To evaluate average switching power in charging and discharging of capacitor we integrate power energy needed to charge to VDD and discharge to ground level while applying input waveform which have zero rise and fall time with time period T

                                        CMOS inverter 

Leakage or Static Power Dissipation:

It occur when circuit is not active or in OFF state. It is a function of the supply voltage (VDD), threshold Voltage (Vth), and transistor dimensions. The main components of leakage current in the scaled devices which also caused power dissipation are shown in figure.

                             Major leakage current component in NMOS

Power Tool Strategy

For calculating Average power

I placed a power meter between power supply and device as shown in figure below and calculate the product of average current and Voltage. For calculating average current i placed one extra power source of 0V in netlist.

              The power meter circuit used for the simulation of average dynamic power

For calculating leakage power

I remove all non constant power supply voltages and calculate the product of leakage current and Voltage. For calculating leakage current i placed one extra power source of 0V in netlist.

Inputs for Python Power Tool

First input is spice netlist. While executing script some more inputs are taken such as

1. Name of Supply Voltage

2. Node name of Supply Voltage

3. For synchronous circuit time perod of clock and for asynchronous minimum time period among all input pulse.

4. User has to remove all non constant voltage sources from the netlist for leakage power.

Python Power tool with example

1.First download or clone this repository.

             git clone https://github.com/CharuGupta-eng/vsdOSPowerCalc

2.To see circuit diagrams of scheamtic, go to images and there are images of circuit by their names.

3. Save the netlist of the cicuit, model parameters file, ngspice and python code in the same folder.

4. To see how we download ngspice, python3 and other useful things which have to download please see below in Python Power Tool Usage (Dependencies) section.

NOTE: This tool work properly in PYTHON3. It sometime create problem in exexution in PYTHON2 so i recommend to use it in PYTHON3 only.

USE PYTHON SCRIPT TO FIND Average POWER

1. To run code

   $ python3 POW.py
        or
   chmod 777 POW.py
       ./POW.py     
   

2. Following window open in which you have to enter .txt file name Or .cir file name as I enter DFF_TG.cir file of DFF using transmission gate.

NOTE : .tran 1e-0 20e-6(end value according to you) line must be present that means transition analysis.

                                           Python scipt 

                                           DFFTG.cir file 

                               Showing supply voltage value and node name on schematic

                                     Showing Time Period In Schematic                                         

4.Finally you get average power value.

PYTHON SCRIPT TO FIND LEAKAGE POWER

1. Run script by writing

        python3 leakage.py 
            or 
       
       chmod 777 leakage.py
       ./leakage.py
   

2.Following window open in which you have to enter .txt file name or .cir file name as I enter TT.cir file of DFF using transmission gate after removing non constant voltage sources (pulse) and no needs to remove any other line.

                                                Python script

3.You get leakage power on ngspice

Python Power Tool Outputs interpretation

Both leakage and average switching power are displayed in Watts. After running POW.py for average power clculation poweranalysis.cir and Leakage.py for leakage power calculation powerleakage.cir file are added in your system. These are modified netlist for power calculation. To view average power curve and power values you can run these netlist in ngspice.

Average Switching Power netlist can be run by following command.

 $ ngspice poweranalysis.cir

Following power plot you get (Depending on your cicuit)

                              Average Power Calculation on NGSPICE(DFFusing TG)

Leakage Power netlist can be run by following command.

 $ ngspice powerleakage.cir

Future Work

For proper working of this tool cicuit must have single power supply source.Hence it can be modified so that it works for multipile supply voltages. I tested this tool for osu 180 and TSMC 180 technologoy parameter file only.

Python Power Tool Usage

Dependencies

This tool works in NGSPICE and PYTHON only. Prerequisite things to run power analysis tool.

About Ngspice

Ngspice is an open source mixed signal circuit simulator.

Installing Ngspice

Open your terminal and type the following to install Ngspice

$ sudo apt-get install  ngspice

Installing Python

NOTE: This tool work properly in PYTHON3. It sometime create problem in exexution in PYTHON2 so i recommend to use it in PYTHON3 only.

Open your terminal and type the following to install Python3

$ sudo apt-get install  python 

NOTE: ngspice shell and python code are in same folder.

To run Python Script to find average power

NOTE: I used panda module so firstly you have to download panda

window user

In command prompt write

pip install pandas

linux or ubuntu users

step 1 : Open your terminal (ctrl + Alt + T), then type these command

sudo apt-get install python3-pip

Step 2: Write this command also

 sudo python3 -m pip install pandas

step 3: When pip installed, type the command to insatll pandas

pip install pandas

NOTE: ngspice shell and python code are in same folder.

Steps to run PYTHON POWER TOOL

Following steps to be followed to run tool to get average power and leakage power of any circuit:

1. To clone respository or download files, Open terminal first and type

     $ sudo apt install -y git
     $ git clone https://github.com/CharuGupta-eng/vsdOSPowerCalc 
   

2. Save the netlist of your cicuit, model parameters file, ngspice and python code in the same folder.

3. .tran line must be in your netlist.

4. To run code for calculating average power

   $ python3 POW.py
       or
   chmod 777 POW.py
      ./POW.py   
   

5. Ener the name of file, Supply voltage name, node name of supply voltage and value of value of supply voltage.

6. Average power value is displayed.

7. To run code for calculating leakage power

   $ python3 Leakage.py
      or
   chmod 777 Leakage.py
     ./POW.py   
   

8. Ener the name of file after removing all non constant voltage source from netlist, Supply voltage name, node name of supply voltage and value of value of supply voltage.

9. Leakage power value is displayed.

Unit of output displayed by power analysis tool

Both leakage and average switching power are displayed in Watts.

If there is an issue running tool, please contact administrator for support or report in “issues” section of GitHub

Contact information.

1. Charu Gupta M.tech VLSI Design and Embedded Systems DTU,Delhi [e-mail]
2. Kunal Ghosh Director, VSD Corp.Pvt. Ltd. [e-mail]
3. Philipp Guhring Software Architect at LibreSilicon Association [e-mail]
4. Dr. Gaurav Trivedi Co Principle Investigator, EICT Academy, and Associative Professor IEEE department IIT Guwahati [e-mail]