Electronic Design

IC Measures Time-Of-Flight With 125-ps Accuracy

Ken Condreva, an engineer at Sandia National Laboratories in Livermore, Calif., had a problem. He needed to accurately record critical timing signals in weapon test flights. But new telemetry systems required a compact, lightweight, low-power device—and there weren't any available.

"The only things I could find that had this resolution were table-top instruments packaged in a box," he said. "They were way too big, and used way too much power." So, he rolled up his sleeves and invented the Falcon.

This inexpensive IC, which is smaller than a dime, is accurate up to 125 ps (see the figure). It uses Condreva's patented "Pulse Stretcher" technique to increase resolution up to 200 times for a low-power clock using 300 mW at 40 MHz.

The circuitry provides greater resolution by lengthening the duration of the output signal to 64 to 200 times longer than the input signal. This technique is similar to recording something with fast-action film and then replaying it at slow speed to clearly see what happened.

Its applications go beyond weapons systems, though. Sandia believes it can be used in anything that depends on accurate distance measurement, such as land surveying, construction, liquid level measurements, and collision avoidance. It can withstand high and low temperatures, high vibration and shock, and high and low humidity.

Scott Vaupen, Sandia's business developer, noted that the circuit uses commercially available standard CMOS technology. Most semiconductor businesses, he added, could manufacture it inexpensively. For licensing information and other details, call (925) 294-2322, or point your browser to www.sandia.gov.

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