Mixed-Digital/Analog Simulation and Modeling Research Prof. Hal Carter 11 February 2005

A Mixed Signal Mixed Domain RF chip RF receivers Microprocessor Frequency domain Digital Core Time domain A/D converters Memory Units RF Transmitters Frequency domain Analog Core Time domain Mixers Courtesy Acapella Ltd

Context Simulation Modeling Electronic Design Automation Digital/Analog Electronics VLSI Data Analysis Applications

VHDL-AMS Example ir il n2 dout n3 entity rl_series is port (dout: out bit;); generic (R : real := 2.0; V : real := 10.0 ; L : real := 4.0 ); end entity ; architecture behavior of rl_series is terminal n1, n2, n3 : real; quantity Vr across ir through n1 to n2; quantity Vl across il through n2 to n3; quantity vs across n1 to n2; begin Vs == V; dout <= NOT a2d (n2); Vr == ir * R; Vl == L * il’dot; end behavior ; ir R n1 n2 dout Vr Vl il Vs n3

Top Down Design with Mixed-Signal Current Language Scope Technology Domain Timing Model Current State of VHDL-AMS Continuous Current State of Digital Design Representation (after synthesis) Mixed Distributed parameter Future State of Analog Design Representation Lumped parameter Discrete Digital Current State of VHDL Time Frequency Physical Domain Representation

Mixed-Signal Design Digital/Analog Behavioral Design Reqts Circuit Design Layout VLSI Circuit Simulate Simulate Analyze Simulation Results Extract & Simulate Analyze Simulation Results Analyze Simulation Results Fabricate

Behavioral Design Analog Behavioral Design Digital Behavioral Design Algorithm Transfer functions Signal flow Interface signals Voltage/current sources Waveforms Functions Digital Behavioral Design Algorithm Sequence of actions Functions Finite State Machines Interface signals Sequences of numbers integer or real types

Circuit Design Digital Circuit Design Analog Circuit Design Component networks Register transfer Level Gates & latches Interfaces Bit scalars and vectors Timing Discrete and accurate Analog Circuit Design Component networks Constitutive equations Kirchoff equations Interfaces Terminals, voltages, currents Timing Continuous & accurate

Mixed-Signal Modeling Methodology Behavioral level (System) Function is primary Include all primary and secondary effects (e.g., noise) Use simulation results as “golden” behavior Subsystem level Subsystem function is primary Include all primary and secondary effects in each subsystem Compare simulation results with behavioral level results Component level (Circuit) Component function is primary Sinclude allprimary and secondary effects in each component Compare simulation results with subsystem level results

Sigma-Delta Converter Example Behavioral Level Behavior output(n) = mult_noise * input(t) + add_noise where output(n) is type “discrete bit” and input(t) is type “continuous real”

Sigma-Delta Converter Subsystem Level Integrate Discretize Serial-to- parallel DAC Int_output = mult_noise * integrate (Int_input) + add_noise

Sigma-Delta Converter Integrate Discretize Serial-to- parallel DAC Voltage = (mult_noise * resistance + add_noise) * Current

Mixed-Signal Simulation C++ Compiler Run-Time System Syntax Lexical Analyzer Static Semantic Analyzer C++ Code Generator Library Pre- processor Elaboration Built-in Attributes Front end additions VHDL-AMS Model Library Manager Initialization Discrete Event Kernel Frequency Kernel Continuous Time kernel Output processing

Data Analysis Many random variables in models Need thousands of simulation runs Simulator must be very fast Need parallel simulator Need to design experiments for efficiency Design of Experiments Data is very complex Need to analyze data statistically

Molecular Computers Idea: Predict logic and memory circuits, Develop models for devices and circuits Create an algebra and design method for nanotube electronics