EDNE July 2012 - (Page 37)

tery power into the traction motor. The high-voltage orange cables leading to this module have disconnects with relays for safety; Steier notes that the module cover itself is also a safetycircuit disconnect. Inside is what Scott-Thomas says is the closest thing to a central brain in the car (Figure 3). freeScale microcontrollerS The Hitachi PCB includes four 32-bit Freescale Qorivva microcontrollers. Scott-Thomas first noticed the large amount of real estate available, noting that it allows future modifications, either by changing or adding circuits. One of the four controllers functions as the supervisor, using inputs, including vehicle and wheel speeds; acceleration, or throttle; braking; and battery state, to decide which state is the most efficient (Figure 4). Decisions to be made could include, for instance, choosing which combination of outputs from the traction motor and combustion-engine-generator motor to use, when to activate regenerative braking, and to what extent to recover energy. The supervisory controller is the largest of the four microcontrollers, with 3 Mbytes of flash memory, taking half the area of the die. The controller also endeavors to run the electric motors at lower rotation rates for more efficiency. The other three Freescale microcontrollers control the traction motor; the combustionengine-driven generator; and the clutched planetary gear set, which the IC engine can engage if necessary. other electronicS The rest of the Volt’s electronics, unless they connect with the hybrid-drive system, are fairly conventional state-of-the-art automotives (Figure 5). An air-cooled dc/dc converter, with PCBs from TDK and a Renesas microcontroller, takes the place of an alternator to provide 12V for running standard auto systems, such as doors, lights, navigation, and audio, and to charge the auxiliary 12V battery. Taking apart the center stack uncovered a communications-module PCB by LG hosting a Freescale memory controller with Spansion flash. These infotainment boards are sparse, according to Scott-Thomas, who notes there is a lot of space but not that much required processing power; thus, the electronics combine several functions onto single chips. In addition, adequate space between the resistive-touch switches on the front of the panel helps prevent the driver from incorrectly selecting the wrong function. As customers gain experience, it will be interesting to see how—and how fast—this plug-in hybrid platform evolves in the coming years. EDN referenceS DeMeis, Rick, “Innovation revelation: engineering the Chevy Volt,” EE Times, May 13, 2011, http://bit.ly/HJSyOx. 2 DeMeis, Rick, “We tear down a Chevy Volt,” EE Times, March 12, 2012, http://bit.ly/HOpY0Y. 3 DeMeis, Rick: “Driving impressions: Chevy Volt,” EE Times, Aug 2, 2011, http://bit.ly/tB3W3U. 1 you can reach Designline editor Rick DeMeis at jldmld@comcast.net. Read more at www.eetimes.com/design/ automotive-design. www.edn-europe.com JULY 2012 | edn eUroPe 37 http://ad.doubleclick.net/clk;256714408;80512663;h?http://www.digikey.com/europe http://www.bit.ly/HJSyOx http://www.bit.ly/HOpY0Y http://www.bit.ly/tB3W3U http://www.eetimes.com/design/ http://www.edn-europe.com

Table of Contents for the Digital Edition of EDNE July 2012

Cover
Contents
International Rectifer
Microchip
FTDI
Masthead
Comment
International Rectifer
Pulse
Analog Devices
Digi-Key
Analog Devices
Test & Measurement
Agilent Technologies
Baker's Best
Messe München
Understand and characterize envelope-tracking power amplifiers
Digi-Key
Cover Story
Coilcraft
Digi-Key
Signal Integrity
Altera
USB 3.0 : Bringing SuperSpeed connectivity to mobile devices
Digi-Key
Developing high-frequency integrated circuits for test and measurement
Design idea
Product Roundup
Tales from the cube

EDNE July 2012