ADMS: Compact Model Synthesis PART I: Introduction and development outlook

ADMS: Compact Model SynthesisPART I: Introduction and development outlook Laurent Lemaitre Freescale - Geneva Ben Gu Freescale - Austin 1

Outline of Presentation • Device Models in CAD tools • Device Model Implementation – hand-crafted • ADMS: software tool - translates Verilog-AMS to C • Overview of the Device Model Generator • Example of Model Generation • Ngspice Interface • Work on progress • Conclusion

Device Models in CAD tool Spice netlists + Process libraries (model parameters) Electrical Circuit Simulator DESIGNER Simulation Results Spectre, ADS, Mica, .. done manually or use model compiler (ADMS) Built-in Device Model EquationsVBIC, EKV, SP, MOSCAP, R3, ..

Model ImplementationHand-crafted • Device Model Engineer: • provides equations of new model • to programmer. No standard. • Programmer: • hand-codes the model in source code of the electrical circuit simulator (most of the time the language is C). No standard. • C code must comply with the Simulator Programming Interface. Much coding needs to be done again for each simulator. • C code involves the manual computation and coding of partial derivatives. This process is tedious and error-prone. • C code is hard to read. Feedback to the Device Model Engineer is made difficult. • The process is a barrier to model maintenance and enhancement.

ADMS Approach • ADMS translates Verilog-AMS to ready-to-compile C code for simulator API (application programming interface) • ADMS uses Verilog-AMS as input. • Advantages of Verilog-AMS: • Verilog-AMS code easy to read - no extra code specific to simulators. • Model can be easily and completely tested prior implementation ! • ADMS uses XML (successor of HTML ) as internal language to build the translators from Verilog-AMS to Simulator API: • Simplifies development of new features of ADMS and support of multiple simulators

ADMS Translator STANDARD 1: AT MODEL LEVEL DTD basedvalidation Verilog-AMS Model Code Parsing STANDARD 2: AT SIMULATOR LEVEL Internal XML program data Other Code Generator applications Testing prior implementation C code Mica, Spectre, ADS, … Documentation Circuit Test benches

Example – Verilog-AMS I `define NPN +1 `define PNP –1 module BIP (c,b,e); // Nodes input c,b; // input nodes output e;// output nodes electrical c,b,e; // all electrical // Branches branch (b,c) bc; branch (c,e) ce; branch (e,c) ec; branch (b,e) be;

Example – Verilog-AMS II // Parameters parameter real is = 1.0e-16; parameter real bf = 100; parameter real br = 1; parameter real nf = 1.0; parameter real nr = 1.0; parameter integer type = `NPN; // Variables real Tdev, Vtv; real Ifi, Ibf; real Iri, Ibr; real argf,expf;

Example – Verilog-AMS III analog begin // Analog section Tdev = $temperature; Vtv = 1.380662e-23 * Tdev / 1.602189e-19; if ( type == `NPN ) begin argf = V(be) / ( nf * Vtv ); end else if ( type == `PNP ) begin ... expf = exp(argf); Ifi = is *(expf-1.0); Ibf = Ifi/bf; begin I(ce) <+ Ifi; // FORWARD Transport C-E I(be) <+ Ibf; // FORWARD Diode B-E end

Example – Code for Spectre SPECTREinterface.h BIPdefs.h BIPinitParameter.c BIPloadJacobian.c BIPevaluateStatic.c BIPevaluateDynamic.c BIPOLAR TRANSISTOR in VERILOG-AMS Run admsSpectre Ready-to-compile C code

Example – Test-bench Circuit • Automatically Generated by ADMS Cint 1 kOhm Bint 1 V 1 kOhm Eint 1 V 1 Ohm

Example – Comparisons

NGSPICE support • Motivation: standardization effort • Link to home page: http://ngspice.sourceforge.net/adms.html • How to: http://ngspice.sourceforge.net/admshowto.html# • ADMS distribution in ngspice: • ADMS is distributed separately from ngspice. You can download the ADMS compiler from it's web site. Once you have downloaded and installed the compiler, you can add Verilog-AMS model to ngspice. • The process of adding a new device is far from being automatic and need a certain knowledge of spice internals. The file README.adms distributed with ngspice describes the process. • Plan: update the XML interface by Q4-2006: integrate the latest versions of psp, hicum and mextram.

Work in Progress • ADMS is written in the C language • Current release 2.2.4 • Next release 2.2.5 planned by end of October • documentation • stronger XML parsers • faster (5X) • ADMS is open-source: mot-adms.sourceforge.net • Port to freeBSD (July 2006)

Work in Progress • Working with Agilent to provide a free MINT interface: • end 2006 • Cadence provides support through CMI • Helene Parruit (ENSIB) writes the QUCS XML interface • Mentor Graphics is currently its XML interface for ADMS • The PSP family used ADMS to release its simkit version • Simucad who uses ADMS to implement some of its models.

Conclusion • ADMS = automatic implementation of compact models into circuit simulators • ADMS automatically generates efficient, robust, correct-by-construction code • (bsim3 same speed as hand-crafted reported in 2 cases) • ADMS has been successfully used for the integration of new device models into Mica, Spectre, HSIM and ADS • Compact models are defined by Verilog-AMS, a standard high-level language

ADMS: Compact Model Synthesis PART I: Introduction and development outlook