Recent figures from Gartner Dataquest indicate annual automotive semiconductor consumption rising from $17.3 billion to $24 billion between 2004 and 2008. And, as vehicle electronic content grows, engineers must seek increasingly integrated and cost-effective solutions for the control ofand interface toin-vehicle systems. This, in turn, is driving demand for in-vehicle networking (IVN) semiconductor devices that combine digital, analog, and high-voltage capabilities in a single IC.
Obvious examples of mixed-signal application specific standard products (ASSPs) for IVN applications include single-chip LIN and CAN transceivers. Now, however, the ability to combine digital circuitry and high voltage capabilities in a single device is leading to much more integrated IVN solutions.
Take, for instance, semiconductors for LIN bus systems used for controlling distributed electrical systems in non-time-critical automotive applications. Such applications include the control of DC and stepper motors for windows, mirrors, and headlamps, or the management of information from sensors for climate control or seat position feedback.
Dedicated microcontrollers with a built-in LIN universal asynchronous receiver transmitter have become available. These microcontrollers are typically used with a companion chip that integrates the remaining slave node blocks such as the LIN transceiver, voltage regulator, watchdog timer, actuator drivers, and sensor interfaces. New high-voltage mixed-signal technologies, however, allow full integration of the key slave node blocks into a single, cost-effective chip built around standard IP modules. Such integration is behind the recent development of a microstepping motordriver ASSP for remote and multiple axes positioning in applications such as light control units for automatic headlamp leveling and turning.
Nevertheless the integration approach sometimes requires embedded application specific IP. In this case, where ASSP solutions are not available, designers are turning to high-voltage mixed-signal technologies to create custom system-on-chip (SoC) solutions. Devices developed using the latest 80V/50V BCDMOS 0.35-µn;m mixed-signal technology, for instance, can incorporate high-voltage circuitry such as motor controller drivers and DC-DC converters, as well as high-precision analog circuits including band gap filters, and analog/digital and digital/analog converters. Total gate counts can exceed 150,000, while available IP blocks cover phase-lock loops, USB interfaces, bus protocol controllers, and controllers for CAN and LIN connectivity. Embedded microprocessor options include ARM7TDMI (32 bit) and 8051 (8 bit) cores, and ROM, RAM, and non-volatile memory, such as high-density flash memory or EEPROM solutions can all be supplied.
One aspect to the integration that needs to be stressed is the proximity of the application environment. In the past, smart electronic boxes were seen in the engine compartment surrounded with wires and cables. The integration of the application functionality in one chip will obviously allow the chip to be located near the module it would control. Being closer means fewer cables in the car as only the IVN cable will supply the information to and from the module. Reducing the number of cables, and their resulting weight, is one of the advantages of the standardization of the vehicle networksand in the end, the vehicle consumes less fuel and emits fewer particles. The drawback, however, is the electronics are exposed to a much harsher environment.
For example, temperature-wise, the electronic module will have to be exposed to a wider range than the usual "40C to 125C automotive ambient temperature standard. The new range could go up to 175C ambient, which translates into a correspondingly much higher temperature for the silicon. The difference between the silicon and the ambient temperature is known as the dissipated temperature, corresponding to the energy the application would dissipate in active mode.
The designers of automotive semiconductor SoCs thus have to deal with a more complex development approach than before as the dissipation of the circuit needs to be monitored carefully to avoid overheating the silicon during application temperature peak. Additionally, the semiconductor reliability engineers need to adapt their qualification procedure to fit the temperature application requirements. Finally, the customer needs to monitor more closely the temperature profile of its application in order to help the semiconductor manufacturers to specify the correct accelerated stress test.
Peak temperatures are often met during 10% of the cumulated active lifetime of the vehicle, which more or less fits with the usual 1,000 hours life test performed at the application maximum operating ambient temperature. The deep submicron technologies used to integrate all these components on a single chip are sensitive to the temperature and the leakages of the silicon need to be correctly modeled to allow the designer to correctly size their system for worse case condition during simulation.
To conclude, the trend to reduce particle emission is broader than the "exhaust pipe process" and has large implications on the full automotive electronics supply chain. The reduction of cable weight contributes to the overall emitted particle bill and leads to a better standardized vehicle network. The increase of electronics in the car has to be compensated by a gain in space that the SoC approach and the IVN standardization allows, but with a broader system know how spread over the automotive electronic market players.
Hervé Branquart, is worldwide automotive strategic marketing manager, Mixed-Signal Business Unit, for AMI Semiconductor.