Role of Flash-Based Electronic Control Units & Networks Toward Enabling Environmental Friendly Vehicles
Manager, Far East Marketing
Automotive Products Group
Microchip Technology Inc.
Environmental concerns continue to mount as the number of automobiles manufactured around the globe reaches 63 million vehicles annually, of which 4 million vehicles annually are manufactured within China. The technological advancements of electronics within the vehicle are being driven by the challenge to make the vehicle safer, more energy efficient and networked. Flash-based microcontrollers are the command center for Electronic Control Units (ECUs). ECUs provide system designers with the flexibility to implement software upgrades, monitoring and diagnostic capabilities, and distributed intelligence systems in response to changing customer requirements or governmental mandates, as required. As the proliferation of ECUs increases throughout the vehicle, the need for aiding in the communication between these sub-systems has changed the paradigm of the automobile into the networked vehicle.
Flash-based microcontrollers are integral components of ECUs because of the flexibility and versatility that they add to the overall system. The reprogrammability of Flash-based microcontrollers allows a system designer to implement changes in a productive manner, thus providing a path for additional cost savings in the development cycle of the ECU. Also, the ability of the designer to be more responsive to the ever-changing requirements of their customer base can create a competitive advantage that is difficult for the competition to emulate. Manufacturing and design flexibility allow the supplier to be responsive to changes that can be caused by a variety of reasons from government regulations to consumers’ demands for different features/functionality to design corrections. Fuji Cho, President of Toyota Motor Corp., urges that “An eco-friendly car is not an idea ahead of its time; it’s an idea that cannot wait”.
Environmental Concerns Being Addressed by Flash Microcontroller Based ECUs
China, the world’s third largest car manufacturing base, is facing a serious problem of automobile-related pollution and soaring levels of oil consumption. Statistics from the State Environmental Protection Administration of China show that China will have approximately 33 million automobiles on the road by 2006 and estimates over 131 million by 2020. Inherent risks to China’s air pollution and diminishing natural resources need to be addressed as the growth trend is expected to continue.
Automobile exhaust emissions contribute 20% of the country’s air pollution problems with carbon monoxide and nitrogen oxide emissions. The Ministry of Science and Technology states that 400,000 cases of respiratory illness are reported annually within China’s 14 largest cities. The increase in automobile fuel consumption threatens China’s domestic oil reserves where 60% of its allocation is dedicated to transportation. As environmental concerns mount, governmental regulations are being driven towards alleviating these problems. Engine controls must meet stricter emission laws and fuel economy standards. The electronic content in engine controls creates a networked, closed-loop system that can manage the emissions and the fuel economy of the vehicle by creating the perfect ratio of fuel/air mixture (See Figures 1 & 2 below).
FIGURE 1: Air Quality Sensor ApplicationFIGURE 2: Air Quality Sensor Hybrid Vehicle Battery Challenges – Increasing Supply to Meet Demand
J.D. Power and Associates, a global marketing information services firm based in the United States, estimates that by 2007, about 410,000 hybrid vehicles will be sold in the United States alone, up from an estimated 70,000 in 2004 and about 47,500 in 2003. The three major suppliers of hybrid vehicle batteries, Panasonic (Japan), Sanyo (Japan), and Cobasys (USA), are the manufacturers of the nickel metal hydride batteries for the most popular hybrid vehicles, the Toyota Prius, Ford Escape, and Honda Civic (See Figure 3 for Battery Monitoring System Circuit Board Example). It is estimated that by 2011, 35 different hybrid vehicle models will be in production worldwide.
As environmental friendly vehicles continue to emerge within the automotive market, hybrid battery suppliers will continue to add resources necessary in hopes of keeping pace with the overall demand. Additional battery suppliers are currently seeking testing approval from the car manufacturers to supply hybrid battery packs but the automakers currently require a year’s worth of testing before approving their designs in production. Cellphone companies are also currently evaluating updating their backup generators for their cell towers to utilize the same battery technology which would then put additional strain on the already short supply.
FIGURE 3: Hybrid Battery Monitoring System
Increasing ElectronicsContent in the Automobile
Advanced usage of electronics within the vehicle can aid in controlling the amount of pollution being generated and increasing the ability to provide systems’ monitoring and diagnostic capabilities without sacrificing safety/security and comfort/convenience features that consumers demand. The electronic content within the vehicle continues to grow and more systems become "intelligent" through the addition of Flash microcontroller based ECUs. A typical vehicle today contains an average of 25-35 microcontrollers with some luxury vehicles containing up to 70 microcontrollers per vehicle. Flash-based microcontroller ECUs are continuing to replace relays, switches, and traditional mechanical functions with higher-reliability components while eliminating the cost and weight of copper wire.
Environmental friendly vehicles fall into one of three classifications: electric vehicles, hybrid-electric vehicles, and fuel-cell electric vehicles. The current technology for environmental friendly vehicles has been of the hybrid variation. A hybrid vehicle (Figure 4 below represents the automotive block diagram of a Toyota Prius Hybrid Vehicle) uses its electric motor for start-up and low- to mid-range speeds. At normal speeds, the power distribution is split between the engine and the electronic battery depending on the acceleration requirements. On-going research is being done in the field of fuel-cell electric vehicle development and is expected to be introduced into the automobile market by 2010. The race to provide more environmental friendly vehicles includes most of the major automotive companies led by the efforts of Toyota, Honda, General Motors, Volkswagen, Ford, Nissan, and DaimlerChrysler.
China has invested more than $100 million in developing new technologies for environmental friendly vehicles led by joint venture partnerships with First Automotive Works Co. (FAW), Shanghai Automotive Industrial Corp. (SAIC), Shenzhen BYD Co., Tsinghua University, and Wuhan University. Hybrid-vehicles and fuel-cell electric vehicles both contain electrical requirements that will drive the need for higher power and higher performance semiconductor content in the future.
FIGURE 4: Hybrid Vehicle Block Diagram (Toyota Prius)
(Source: Toyota Motor Company)
Key Technologies for Flash Microcontroller Based ECUs
Flash microcontroller based ECUs are emerging throughout the vehicle, enabling more efficient subsystems from engine management to climate controls to air quality sensor controls to battery monitoring. Automotive ECUs must have Flash-based program and data memory, low power characteristics, and support network protocols, such as CAN and LIN, to support the stringent quality and performance standards needed within the automotive environment.
Flash-Based Program and Data Memory
The non-volatile memory (NVM) cell is the foundation for any Flash technology. Endurance, data retention, temperature, operating voltage and frequency, and programming time all play significant roles in matching the right technology with the application. These parameters are also critical to the reliability of the device. All Flash is not created equal. Many Flash cell designs exist since one design cannot satisfy all requirements of the application. All factors should be considered when selecting the right Flash cell technology for microcontrollers that are to be used in applications within the vehicle. The following are critical characteristics that should be weighted heavily:
Outstanding reliability over the widest operating range of temperature and voltage
Cost-effective programming time
Supports both program and data arrays effectively
Low-power consumption is becoming a key competitive differentiator in electronic modules due to the following reasons: 1) The number of electronic modules is increasing within the vehicle, 2) battery size cannot increase to keep pace due to size, weight, and cost constraints, and 3) greater load demand causes battery failures. Automotive designers are facing tightening total vehicle current limits (typically 20mA – 30mA). Numerous applications within the vehicle are requiring current loads to be present while the ignition is off (keyless entry, anti-theft detection, remote start, sensors, infotainment, etc.). These applications require microcontrollers that have flexible oscillator configurations, fast startup, and various low-power modes (see Figure 5 below). The PIC18F product family from Microchip Technology is representative of the type of Flash-based microcontrollers that take advantage of these types of features to provide a low-cost single-chip solution for power-managed automotive applications with or without integrated CAN.
(Source: Microchip Technology Inc.) Analog & Digital Peripheral Integration
Over the last decade, the integration advancements of analog and digital peripherals coupled with the Flash memory technology has enhanced the performance range of the microcontroller, regardless of the microcontroller bit width. A variety of Flash-based microcontrollers now integrate high-precision analog peripherals such as: analog-to-digital converters, comparators, op amps, brown-out detectors, low-voltage detectors, temperature sensors, internal oscillators, voltage references, EUSARTS, PWMs, programmable timers, and CAN/LIN modules. The Flash-based microcontroller’s integration supports the advancements of standalone electronic control units which are networkable and the reduction of component count and board space substantially reduces the overall system cost.
Space-Saving Packaging Technology
Semiconductor packaging has made considerable advances within the last decade to aid in assisting automotive designers to cost effectively reduce the physical size of sub-system designs, thus allowing for viable alternatives to traditional mechanical solutions. Innovative packaging techniques have allowed system designers an unprecedented level of flexibility when implementing Flash-based microcontrollers in space-constrained applications within automotive designs. In an effort to continually cost reduce not only systems, but also the processes with which these systems are built, design for manufacturability becomes an important issue. The recent packaging innovations of Flash-based microcontrollers help make these designs more adaptable to the harsh automotive environment. Flash microcontrollers come in numerous packages from new innovations with 6-pin SOT-23 packages to extremely I/O intensive 144-pin packages, giving a system designer the ability to utilize the benefits of their flexibility. This packaging trend is expected to continue as automotive manufacturers demand reduced design cycles, lower total system costs, and faster time to market without sacrificing dependable delivery and quality.
A large portion of the automotive applications within the vehicle contains distributed intelligence driven though a variety of Flash-based microcontrollers. Automobiles typically have several networks that contain numerous network nodes. The ability of these systems to work effectively is directly related to gathering data within the automobile. This data is obtained through various sensors (inputs) which is then calculated within the microcontroller and sent back to controlling actuators and switches (outputs). Intelligence is being implemented in these sensors and actuators based on the information from the microcontroller to essentially create smart sensors. Smart sensor technology is referred to as Micro-electro-mechanical Systems (MEMS) that combine silicon semiconductor chips that incorporate sensor, information and signal processing, and control circuits. MEMS devices have the ability to respond to change in temperature, pressure, or other environmental conditions, provide two-way communication, and have self-diagnostic and self-calibrating capabilities. As these devices become more economically viable, smart sensors will provide automobiles with more flexibility in distributing processing capabilities throughout the vehicle and lead to more flexible and reliable systems. The ability of these various sub-systems to communicate within a vehicle network becomes more critical as the intelligence within the sensors increases and sharing of common sensor input and system status becomes a necessity.
Staying Connected – CAN & LIN Protocol Overviews
The typical automobile network is comprised of several sub-system networks (nodes). Strategy Analytics, a market research company based in the United Kingdom, estimates that 611 million automobile multiplex nodes will be installed in vehicles produced in 2005 and forecasts this to increase to 1.2 billion by 2011 (Source: Strategy Analytics: Automotive Multiplex Network Growth – December 2004). The Controller Area Network (CAN) and Local Interconnect Network (LIN) have become the automotive standards for communication protocols within the vehicle especially for body control applications. The CAN and LIN protocols are complementary standards depending on the speed and the cost associated with the application.
Controller Area Network (CAN)
The CAN protocol is the predominant global standard for medium speed (ISO11519 - Class B: 10Kpcs – 125Kbps) and high-speed (ISO11898 - Class C: 125Kbps – 1Mbps) event-driven automotive communications networking. High-bandwidth, real-time control applications like powertrain, airbags, and braking need the 1Mbps speed of CAN and their safety critical nature requires the associated cost. This protocol is error-sensitive and operates on a 5V differential bus.
Local Interconnect Network (LIN)
The LIN protocol is a single-master multislave bus that communicates via a single wire, cost-effectively reducing wiring complexity. It typically is a sub-bus network that is localized within the vehicle and has a substantially lower implementation cost when compared to a CAN network. It serves low-speed, low-bandwidth (Class A: 20Kbps) applications like mirror controls, seat controls, fan controls, environmental controls, and position sensors on a 12V single wire bus. Because this protocol is self-synchronizing, it allows the slave nodes to operate from a low-cost RC oscillator.
The networks, such as CAN and LIN, are very important in view of the increasing number of electronic control units within the vehicle (See Figure 6 that illustrates various automotive applications networked within the vehicle). The networks facilitate the transfer and sharing of information among the electronic control units throughout the vehicle. Ultimately, the efficiency of the vehicle is improved because of the information sharing capabilities of the electronic control units.