Role of Flash-Based Electronic Control Units & Networks Toward Enabling Environmental Friendly Vehicles

By

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.

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.

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.

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.

(Source: Toyota Motor Company)

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.

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:

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  Outstanding reliability over the widest operating range of temperature and voltage
  
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  Cost-effective programming time
  
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  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.

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.

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.

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.

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.

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.

In the face of the continuing challenges that today’s designer is confronted with in the automotive electronics arena, the selection of a compatible, Flash-based microcontroller is very important. Being the core of an ECU, this is a building block which must provide the designer with the flexibility and breadth of compatible devices to solve his design requirements for the next project as well as subsequent projects. The combination of low-power characteristics, Flash-based program and data memory, and support of CAN and LIN network protocols continue to advance tomorrow’s automobiles with the ability to provide the driver with a safer, energy efficient, and more reliable vehicle. Environmental concerns and the quest to provide fuel-efficient, environmental friendly vehicles are becoming an everyday concern for consumers not only in the automotive market but in our daily lives. Governmental legislation, consumer influence, and automakers themselves are driving current and future initiatives to increase the content of Flash microcontroller based electronic control units and networks within the automobile without sacrificing consumer convenience.