Test gears up for 42-V automotive ICs

The HVD instrument tailors the Flex ATE system for automotive IC applications, adding features such as -20-V to +70-V measurement capability and fully automated hysteresis test. Courtesy of Teradyne.

Several factors, Boydston said, are slowing the move toward 42 V, including the "jump-start problem" and the greater propensity for arcing at 42 V. Nevertheless, he said, the promise of less copper makes the move to 42 V inevitable.

He added that while waiting for the automotive industry to ramp up to the 42-V standard, companies who install a high-voltage test system will gain interim benefits: They can use the tester for printer and other non-automotive applications that employ high-voltage ICs to drive higher-voltage, and therefore smaller and lighter, servos and stepper motors.

Boydston cited a variety of automotive 42-V IC test challenges. The obvious requirement is instrumentation capable of sourcing and measuring the required voltages and currents. Complicating such testing is the coexistence of high-voltage and low-voltage mixed-signal circuitry within one device.

A related problem is the need to test all device pins—including low-voltage ones—for high-voltage leakage, because low-voltage pins may be exposed to high voltages through shorts. In addition, high- and low-voltage functions within a device are interdependent, and their tests can't be performed in isolation, as they could for high- or low-voltage-only parts destined not to meet until combined on a PCB. Finally, many automotive functions rely on hysteresis to prevent false triggering on sensor outputs in noisy automotive environments, and hysteresis tests can consume considerable test resources and be difficult to program.

To address these challenges, Teradyne developed a suite of instruments, including the HVD high-voltage digital board, to adapt the company's Flex ATE system for automotive IC applications. As one of its features, the HVD provides fully automated hysteresis test capability for all DUT pins in multisite applications.

But the individual instruments themselves aren't sufficient to achieve high-throughput test, Boydston added; they also must play well together.

To do that, said John Rowe of Teradyne's Semiconductor Test Division's platform applications group, Teradyne's Flex tester employs a pattern-control architecture, in which each instrument board includes a pattern-generator ASIC referenced to a central time base. Each instrument can control its own timing and maintain time synchronization with other instrument boards without being dependent on host computer speed or operating-system jitter. The Flex augments its pattern-control architecture with a parameter-set feature that can rapidly alter the instrument state under pattern control to speed test throughput.

The alternative to Flex's approach to automotive IC test, said Boydston, is to "build a tester on a tester"—that is, to add substantial test circuitry to a device interface board. That approach, he said, introduces correlation problems, with repeatability tough to guarantee. The tester-on-a-tester approach worked in the past, he said, "but with the liability issues posed by components for ABS and airbag deployment, it's becoming totally unacceptable."