Autonomous Vehicle Timing is a MEMS Thing (.PDF Download)

Engineering is always about tradeoffs, but autonomous vehicles are pushing that to the limit with conflicting requirements.

• These vehicles will generate copious amounts of data, both from the various forms of vision sensors as well as environmental sensors detecting temperature, pressure, and other critical parameters.
• Communication will be constant, using automotive Ethernet internally and 5G to talk to the world.
• They operate in an unforgiving environment, with constant vibration and shock. Temperatures can be extreme, due to external weather as well as the internal engine temperature. Temperature changes can be rapid, both externally, with quick weather changes, and internally, for example, when the engine warms up. Moisture can materialize at any time due to rain or driving on wet pavement.
• Automobiles put lives at stake. A car should always work, but if something goes wrong, it must be able to behave well as it moves into a safe state.
• Cars are a consumer item; manufacturers are extremely cost-conscious, even as they demand high performance from their electronics. Chip footprints must be small to save area, and electronics must be manufacturable with high yields to keep prices in range.

One common thread runs through all of these requirements, and it’s one we usually take for granted: timing. For everything to work in lock-step, even if things go awry, those clock signals must operate without fail. Timing is now mission-critical, more than it has ever been before, placing extreme demands on the sources of that timing.