AVOSpice is a fast and accurate simulation module for to use in the analog design of VLSI (Very Large Scale Integration) circuits. It combines the advantages of SPICE and fast-SPICE programs. AVOSpice applies specific data structures and mathematical methods that provides with the improved efficiency in the time it takes to simulate without a loss in accuracy. It is running both under Windows and Linux.

Key Features

• Simulates VLSI circuits at the transistor level.
• Performs functional verification of complex digital-to-analog projects such as SoC projects using precise (SPICE) simulation methods.
• Applies fundamentally new calculation algorithms for speeding-up the circuit simulation process.
• HSPICE/Spectre compatible for mixed netlists, models and analyses.
• HSPICE/Spectre correlation.
• Makes TRAN analysis of complex projects within commercially acceptable time frames.
• Monte Carlo analysis.
• Supports multiprocessing/multicore operations.
• Provides integration with Cadence Composer through AVOSpice Simulation Environment.
• Performs RC network reduction.
• Delivers the performance and capacity required to perform overnight analysis of complex analog circuits with up to one million transistors with SPICE accuracy (for PC with 4Gb RAM).

Accuracy
A new technology of calculations was realized which allows to accelerate substantially circuit simulation without making accuracy tradeoffs. As a result, accuracy level provided is as high as one delivered by commonly used SPICE simulation programs.

Accuracy Comparison
The comparison was carried out on time-delay circuit providing time delay of 2.1ns. Below the table with comparison results is represented.

Table 1. Accuracy Comparison Results

Simulator	Time delay, ps	Maximum spread in values, ps
AVOSpice (1)	2 081	13
AVOSpice (2)	2 094
Simulator A(1)	2 066	33
Simulator A(2)	2 099
Simulator B(1)	2 010	57
Simulator B(2)	2 067

Simulator A and Simulator B – SPICE simulators
(1) – with automatic step selection
(2) – with step ≤20ps

Depending on different simulation options various simulators deliver different results. AVOSpice applies specially developed methods providing high level of simulation accuracy for the majority of circuits by default.
On the picture above You can see that simulation results generated by AVOSpice have minimal spread in values and AVOSpice curves are located within curves generated by other SPICE simulators (at minimal step of integration).

Capacity
AVOSpice can simulate up to 1 million elements: resistors, capacitors, inductors, transistors (PC 4Gb RAM). The most advantage can be obtained for circuits of size from thousands to hundreds of thousands transistors (500.000).

Speed

• Typical DAC circuits:
  AVOSpice simulates from 2 to 7 times faster than other SPICE simulators.
• Complicated digital circuits consisting of up to hundreds of thousands transistors:
  Acceleration achieves hundred and thousand times in comparison with other SPICE simulators.

Calculation technology
AVOSpice applies unique technologies for calculations that allow speeding up calculation processes. It was achieved due to the following distinctive features of AVOSpice technology.

• Mathematical methods, algorithms and rules system developed allow classification and separation of circuit variables (potentials) into groups. These groups are generated dynamically at the certain time interval, it allows:
  • dividing a big system of algebraic equations into a set of independent subsystems in the majority of cases. Solving such subsystems separately leads to significant decrease of computation resources;
  • applying mathematical algorithms according to individual peculiarity of each subsystem;
  • using multiprocessor calculations, which means that every group of variables is processed in a separate processor.
• The main resources are spent to simulate only active part of circuit, while the accuracy is the same as for full circuit.
• Conventional algorithms were redesigned in order to save time at the expense of memory (usually algorithms save memory and time simultaneously).
• Original data structure efficiently using processor cache memory was designed.
• Effective parallelization using pool of threads.

Due to applying these technologies AVOSpice simulates with speed of fast-Spice without loss in accuracy.

Table 2. Simulation Results

Program	Circuits
	Generator 5713 (BSIM3)	PLL 1607 (BSIM3)	ADC10 4933 (BSIM3)	USB Cable 12141 (BSIM3)
AVOSpice	8h 08min	2h 13min	3h 02min	6h 46min
SPICE simulator	2 days 14h	7h 09min	9h 53 min	2 days 2h
	6 times faster	3 times faster	3 times faster	7 times faster

Multiprocessing

The challenge of multithreaded programming is very acute, as the market is changing and multicore systems become more and more affordable for IC designers.

AVOSpice is fitted to using on multicore systems due to applying of original algorithms which allow efficient paralleling. This results in extra acceleration of calculation process.

Analyses
Supports all main types of analysis: 

• transient (.TRAN);
• direct current (.DC);
• frequency (.AC);
• sweep for all analyses mentioned above;
• Monte Carlo analysis.

Design Flow
AVOSpice easily builds into the following design flows:

• running from command line;
• running from Cadence Schematic Program through AVOSpice Simulation Environment.

Models Available

• Resistor, physical resistor, capacitor, inductor.
• Diode: LEVEL1 (nongeometric junction diode model), LEVEL3 (geometric junction diode model).
• BJT: Gummel-Poon, HICUM 2.1, VBIC 1.2, MEXTRAM (bjt504, bjt504t, bjtd504 and bjtd504t).
• MOSFET: BSIM3v3.2, BSIM4, BSIM4.5.0, EKV 2.6, EKV 3 (Electronics Laboratory–TUC).
• JFET.
• Independent sources: Pulse, Exp, Sin, PWL, SFFM.
• Dependent sources: VCVS, VCCS, CCCS, CCVS.

Inputs

• Netlist in HSPICE format.
• Netlist in Spectre format.
• Mixed HSPICE /Spectre netlist.

Outputs

• PSFBIN / PSFASCII;
• CSDF (ASCII);
• NUTMEG;
• CSV (ASCII);
• Monte Carlo data;
• measurement data.

Recommended System Requirements:

• AMD 64 Opteron 2.2 GHz;
• 1 Gb RAM.

Operation Systems:

• Linux: SuSe 9.2, 10.0, RedHat 7.3(x86) and others;
• Windows 2000, 2003, XP, Vista.