A Collaborative Design Approach to Interdisciplinary Mixed-signal SoCs for Automotive Applications Nyambayar Baatar1 and Shiho Kim2 1
Department of Electrical Engineering, Chungbuk National Univ School of Integrated Technology and Yonsei Institute of Convergence Technology Yonsei University Songdo, Incheon 406-840, Korea
[email protected]
2
Abstract— A collaborative design approach to interdisciplinary mixed-signal SoCs for automotive applications is presented. Mixed-signal SoC design for vehicles involves the collaborative blending of mixed-signal systems with convergence among multidisciplinary areas of technology such as mechanical, MEMS, and semiconductor technologies with analog and digital signal processing. The key features of this approach include a system knowledge-based control algorithm, collaborative design, rapid prototyping, mixed signal interoperability, and intelligent information processing.
I.
INTRODUCTION
A mixed-signal IC is any integrated circuit that has both analog circuits and digital circuits on a single chip. Typical mixed-signal integrated circuits are data converters, amplifiers, filters, display drivers, sensor interfaces, etc. With the advances in semiconductor technology and system performance, application specific integrated circuits often contain an entire system-on-a-chip, including CPUs, network and communication units, embedded software, and analog and RF circuits. Because of their use of both digital signal processing and analog circuitry, mixed-signal ICs are usually designed for a very specific purpose, and their design requires a high level of expertise and careful use of electronic design automation (EDA) tools. Despite tremendous advancements in the areas of computer aided design tools and methods, there are specific challenges in the design of mixed-signal systems on chip (SoCs): •
The CMOS technology and supply voltage are usually scaled for digital performance, making it difficult to achieve both analog and digital performances in a single technology.
•
Although design automation is practical and essential in digital design, analog circuits are not well suited for automation. Combining analog and digital technologies multiplies the complexity of the design.
•
Fast switching digital signals generate noise, which is transmitted to sensitive analog parts. One path for this noise is substrate coupling. A variety of techniques are used to attempt to block or cancel this noise
coupling such as fully differential topology, on-chip decoupling, guard-rings, and triple-well isolation. •
Verification in the design step and the testing of chips can also be challenging.
Technological convergence is the trend for technologies to merge into new technologies that bring together a myriad of media. Conventionally, technology has handled one medium or at most two tasks. Through technological convergence, devices are now able to present and interact with a wide array of media. The needs of this new paradigm require designers to understand a broad range of disciplines, from the solid state physics of nano-scale devices, through circuit-level techniques, to high level system design [1]. In addition to theoretical knowledge, a designer must also be constantly aware of manufacturability and testability issues. The increasing complexity and pressure on researchers and developers of interdisciplinary convergent technology have caused them to adopt a collaborative design approach [2]. This paper describes a collaborative design approach to the design of mixed signal integrated circuits for automotive applications. The examples that will be described in this paper include a platform-based design to overcome the complexity of academic interdisciplinary projects involving mixed signal SoC design. II.
COLLABORATIVE APPROACH FOR INTERDISCIPLINARY MIXED SIGNAL SOC DESIGN
Collaborative technologies can be used to facilitate solutions to problems in the design and implementation of integrated electronic systems such as advanced control, communications, and intelligent systems [2]. The goal is to provide a solution for the proper definition, identification, and application of mixed domain technologies for SoC development involving multidisciplinary and collaborative design. These elements are crucial aspects of evolving a successful integration of interdisciplnary convergent technology into SoC. This approach is necessary because the new collaborative technology is creating paradigms for large complex microsystem design, which requires the use of multidisciplinary skills throughout the SoC development
III.
Selection of Circuit Topology Interoperability Optimization
System Knowledge Based control Algorithm
Multidisciplinary System Requirements
Performance Constrains Critical Time Domain
Mixed-signal Circuits Back-end design
To Manufacturing
Fig. 1. Collaborative approach for design and fabrication of interdisciplinary mixed signal SoCs.
environment. For a collaborative approach, as shown in Fig. 1, the simulation tools must be interactive, graphical, and fully integrated into a multidisciplinary framework to provide a fully integrated, interoperable, interdisciplinary mixed signal SoC design. The collaborative goal of SoC design can be ranked by its effectiveness in determining time critical task decisions and information gathering, identification, retrieval, and fusion. The system knowledge-based functionality algorithm provides the perception element for the mixed signal SoC. Collaborative micro-models must therefore contain accurate representations of the scaled technology, account for the effects of advanced materials, and provide mixed-signal interoperability. To ensure the performance of these mixed-signal designs, they must incorporate domain technologies for verifying, validating, and ensuring the functionality and integrity. While design automation is practical and essential in digital design, analog circuits are not well suited for automation. Analog designs are typically transformed from concept to implementation by hand, which makes the design slow and error prone as compared to automated digital circuit design. As an alternative to design automation, analog designers have to develop a bottom-up design methodology that is more efficient [3-4]. The traditional bottom-up design process starts with the design of individual blocks, which are then combined to form the system. The block design starts with a specification and ends with a transistor level implementation. Each block is verified against its specification. Once verified separately, the blocks are combined and verified together at the transistor level. A comprehensive verification strategy, including simulation and modeling plans, is needed. The plans specify which tests to run, how to perform them, and which blocks shall be at the transistor level during the test. For blocks represented by models, the effects that must be included in the model are identified for each test. The simulation plan is applied initially to the high-level description of the system, where it can be quickly debugged. Once validated, it can be applied to transistor level simulations. Mixed level simulations verify the block function in the system context. Each level is fully designed before moving on to designing the next level.
DEVELOPMENT OF MIXED SIGNAL SOC FOR AUTOMOTIVE APPLICATIONS
Up to 60 million cars are manufactured every year, and with the increasing importance of electronics within a vehicle, vehicle applications provide an attractive opportunity for the developers of mixed signal SoCs. This trend is measured by the growing number of electronic control units and the increasing popularity of mixed-signal SoCs [5]. The integration of various analog functions and IPs supporting invehicle communication on a digital MCU is one of the major trends in the automotive semiconductor arena. The advantages of mixed signal technology include better reliability, superior noise performance, lower cost, smaller size, lower power requirements, and better performance. The reliability is improved by reducing the number of chips required for an application, which means fewer interconnections and less potential for trouble from connector-related problems. Mixed signal devices offer superior noise performance, because fewer chips mean fewer high-speed signals traveling between chips. It is usually cheaper to have a single chip rather than multiple chips, and while a smaller size is not a significant factor for many automotive applications, it could become increasingly important in applications such as battery monitoring. The lower power consumption potential of mixed signal devices is likely to become more important in automotive applications. When you put a data converter on an MCU, it draws less power than it would by itself. It also improves performance, because its data is available immediately to the MCU. MEMS has brought about a revolution in the design of SoC systems because of its multidisciplinary collaborative nature. The collaborative revolution that MEMS is imposing on SoC design involves both macro and micro issues. In macro collaboration, the design team’s environment needs to be collaboration-friendly. The knowledge-based functionality algorithm provides the perception embedded intelligence to perceive patterns, order, and variations. Multidisciplinary domains such as those in MEMS provide a complete set of systems for interoperability; however, they must be optimized to the performance design requirements by using functional measures of collaboration effectiveness. The capability of manipulating data to create knowledge is the thread that pulls together the collaborative processes of design, interoperability, domain data POWER TRAIN
CAR INTERTAINMENT
Engine control On Board Diagnostic Automatic Control System
Automotive Navigation System Telematics Multimedia System
CHASSIS Steering Control Break Control Suspension Control
BODY Body Control Module Electric Lamp Control Unit Convenient Apps Control Unit
Fig. 2. Typical electric system configuration for vehicle.
sensors
Processors
Sensor
Signal conditioning
ADC
Sensor
Signal conditioning
ADC
Mixed signal
Automotive systems
Mechanics
ECU
Sensor Interface Sensor
Signal conditioning
ADC
Sensor
Signal conditioning
ADC
Actuator
Output Driver
DAC
Actuator
Output Driver
DAC
B U S
CPU
System Software
Actuator Interface
Network
Controls
Actuator
Output Driver
DAC
Actuator
Output Driver
DAC
Fig. 4 Configuration of typical sensor and actuator interface circuits of vehicles. Fig. 3. Collaborative interoperability for SoC design of automotive systems.
transformation, information query, and control. Therefore, in successful smart SoC, the collaborative design tasks are evaluated for effectiveness in terms of the probability of recognition and speed of information fusion. Generally, the system environment has a mixed signal nature, dominated by the analog behavior of actuators and loads. Such a mixed signal system is controlled by a microcontroller, which transmits and receives digital data from Smart Power ICs and sensors, typically input, status, and sensor signals. The analog/digital interface is located in the smart power IC and sensors. The smart power IC converts the digital input signals into analog current and voltage characteristics, while simultaneously sending digital status information to the microcontroller. On the other hand, the sensors convert physical parameters like pressure, distance, and temperature into digital information. An electromechanical transformer and mechanical load close the feedback loop by delivering physical quantities to the sensors. The increasing functionality and, hence, complexity requires advanced simulation tools. In the past, the most commonly used approach to simulate mixed signal systems was “CoSimulation,” where digital and analog parts are simulated by individual simulators such as SPICE and Verilog logic simulators and linked by data exchange and command interfaces. Some clear disadvantages of this approach are the inherent incompatible of modeling languages and the low simulation speed [6]. In the EMI (electromagnetic interference) domain, there is a tradeoff between disturbance filtering and signal quality. The experimental verification of such effects is indispensable, as well as time-consuming and expensive. Simulation can help to guide efficient test series. The design gap for analog circuits continues to grow, and system simulation on the transistor level is no longer feasible because of the increasing complexity. A high risk for IC redesign exists because of the lack of top-level simulations. For collaborative interoperability for the SoC design of automotive systems, all aspects of electrical engineering, along with some aspects of mechanical engineering, computer science, and materials engineering are present.
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Power circuits: the electrical motor, power electronics, and power supply.
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Controls: design of a control system for speed control and collision protection, an automatic light control system.
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Processors: control and digital signal processing.
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Mixed signal circuits: mixed-signal interface electronics, sensor interfaces, and actuators, along with hardware realization of the speed control loop and embedded software on MCUs.
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Networks: in-vehicle and vehicle-to-vehicle network.
•
Sensors: sensing physical, chemical, and electrical properties
In this way, a vehicular platform like AUTOSAR (AUTomotive Open System ARchitecture) represents a paradigm shift in automotive software development, from an ECU-based approach to a function-based approach. AUTOSAR is an open and standardized automotive software architecture, jointly developed by automobile manufacturers, suppliers, and tool developers [7]. The need to build a common architecture became stringent for a variety of reasons. The objective is to create and establish open standards for automotive electric and electronic architectures that will provide a basic infrastructure to assist with developing vehicular software, user interfaces, and management for all application domains. This includes the standardization of basic system functions, scalability to different vehicle and platform variants, transferability throughout the network, and integration from multiple suppliers. The model is supported by an automated methodology to create executable software for the ECUs, starting from the design model and the properties and physical topology of the hardware. The principal aim of platform-based standard design is to master the growing complexity of automotive electronic architectures. The goal is to define a common understanding of how electronic control units (ECUs) cooperate on the same functions and separate the software from the hardware in order to allow software reuse
hardware description languages, design analysis tools, physical design tools, and design synthesis tools. The establishment of a platform-based design approach bridges the design gap of the bottom-up approach and will provide a collaborative design methodology by reducing the cost and time needed for SoC design. V.
Fig. 5. AUTOSAR software architecture–components and interfaces [7].
and smooth evolutions limiting re-development and validation. A platform-based approach enables multiple different functions such as software modules to be hosted on the same ECU, independently of the supplier of either part. IV.
DISCUSSION
In automotive systems, designing application specific mixed signal SoCs continues to be a major challenge. The challenge is for semiconductor engineers to understand multidisciplinary system knowledge and manage the design and development of both the software and hardware for this new collaborative methodology. The main tasks of collaborative and multidisciplinary SoC design include: (1) convergence technologies for automotive applications, with mechanical and control algorithms and (2) integrating a mixed-signal SoC with analog, RF, digital, and embedded software. One of the most complex problems in this area is the generation and coupling of noise. For a successful design, the optimization of the interoperability of mixed-signal systems is crucial. The optimization of the interoperability involves the collaborative blending of mixed-signal systems with the multidisciplinary areas of mixed-technology domains for the electrical, mechanical, and mixed-concept performances of electrical, control, and digital signal processing. The meshing of mixed signal design differences imposes robust design challenges for a multidisciplinary design methodology. Integrating application-specific signal processor cores, memory, analog, and MEMS functions on a single chip involves a collaborative design methodology in both the macro and micro arenas. Macro collaborative automation tools reflecting rapid prototyping techniques enable teams of designers to work together from remote sites. Micro collaborative approaches to SoC submicron manufacturing requires advances in interoperability simulation technology,
CONCLUTIONS
The collaborative trend for interdisciplinary mixed-signal SoC design for automotive applications was presented. Mixed signal SoC design for vehicles involves the collaborative blending of mixed-signal systems with the multidisciplinary areas of technology convergence among mechanical, MEMS, and semiconductor technologies, with analog and digital signal processing. The system knowledge-based control algorithm, collaborative design, rapid prototyping, interoperability of mixed signals, and intelligent information processing are the key features of this approach. The collaborative concerns and domain engineering issues for interdisciplinary projects are primarily related to the areas of application-specific mixed signal SoC design. ACKNOWLEDGMENT This work was supported by the Ministry of Knowledge Economy (MKE), Korea, under the “IT Consilience Creative Program” supervised by the NIPA (National IT Industry Promotion Agency) (NIPA-2010-C1515-1001-0001). REFERENCES [1]
[2]
[3]
[4]
[5] [6] [7]
John A. McNeill and Richard Vaz,“Integrating Mixed Signal IC Design Research into a Project-based Undergraduate Microelectronics Curriculum,” Proceedings of IEEE International Conference on Microelectronic Systems Education, p 28- 29, 1997 R. L. Ewing, H. S. Abdel-Aty-Zohdy, and G. B. Lamont, “Multidisciplinary Collaboration Methodology for Smart Perception System-on-a-Chip (SoC),” Analog Integrated Circuits and Signal Processing, Vol. 28, p 181–192, 2001 Martin Anderson, Johan Wernehag, Andreas Axholt, and Henrik Sjöland, “Teaching Top Down Design of Analog/Mixed Signal ICs Through Design Projects,” Proceedings of 37th ASEE/IEEE Frontiers in Education Conference. p T1C1-T1C4, October 2007 Walter Daems, Bart De Smedt, Piet Vanassche, Georges Gielen, Willy Sansen, and Hugo De Man, “PeopleMover: An Example of Interdisciplinary Project-Based Education in Electrical Engineering," IEEE TR. On Education, Vol. 46, No. 1, February 2003 “Auto market holds appeal to mixed-signal IC vendors,” Power electronics technology, January 2005 Dieter Metzner, and Jürgen Schäfer, “Architecture Development of Mixed Signal ICs for Automotive Application with VHDL-AMS “Specification of the Virtual Functional Bus," www.autosar.org
