Teradyne, Inc.

William J Bowhers

Sean Patrick Adam

Jason A Messier

Bryce M Wynn

Michael R Ferland

An example test system includes an output stage to source at least one of voltage or current to a channel of a test instrument; a tracking circuit to detect a channel voltage following the output stage and to control a supply voltage to the output stage based on the channel voltage; and a controller to determine a power dissipation of the output stage based on the supply voltage and the channel voltage, and to control the output stage based on the power dissipation in the output stage.

Controlling power dissipation in an output stage of a test channel

An apparatus and method for deskewing single-ended signals from different driver circuits of an automatic test system provides enough of a reduction in skew to allow differential signals to cross at or near their 50%-points. In accordance with this technique, first and second driver circuits are respectively coupled to first and second inputs of a measurement circuit through pathways having known and preferably equal propagation delays. The first and second driver circuits each generate an edge that propagates toward the DUT, and reflects back when it reaches a respective unmatched load at the location of the DUT. In response to the edge and its reflection, the first and second inputs of the measurement circuit each see a first voltage step and a second voltage step. The interval between the first and second voltage steps is then measured for each input of the measurement circuit. Variable delay circuits disposed in series with the driver circuits are adjusted in response to the measured intervals, to ensure that signals from the first and second driver circuits arrive at the DUT at substantially the same time. The measurement circuit may also measure the slew rates of the signals from the first and second driver circuits. Slew rate adjustment circuits provided with the driver circuits are then adjusted to substantially equalize slew rates from the first and second driver circuits.

Calibrating single ended channels for differential performance

Improved pin electronics for automatic test equipment are disclosed which compensates for the effects of round-trip delay on signals transmitted by the pin electronics and a circuit under test along the same transmission line. The pin electronics includes a driver and comparator circuitry, both of which are coupled to a transmission line connecting the pin electronics to a node of the circuit under test. Signals produced by the pin electronics and the circuit under test are combined at the pin electronics due to the effects of round-trip delay between the pin electronics and the circuit under test. The comparator circuitry takes a scaled version of the signal produced by the pin electronics and subtracts it from the combined signal, thereby recovering the signal produced by the circuit under test. Other pin electronics are also disclosed that uses the scaled signal for modifying threshold voltages provided to the comparator circuitry, thereby facilitating measurement of the combined signal.

Compensating for the effects of round-trip delay in automatic test

Apparatus for automatically testing electronic circuits and performing time measurements, including a time measuring circuit for counting clock pulses provided between stop and start event edges presented to it, two independent input selectors for each selectively connecting one of a plurality of its inputs to the time measuring circuit, and a plurality of local comparators located within the test apparatus near sources of signals to be timed and generating an event edge upon receiving a signal crossing a threshold value. Also disclosed are making time measurements of signals at digital and analog pins using local comparators connected to input selectors over deskewed transmission paths and connecting a local comparator to the filter output of an analog instrument.

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Wayland, MA, United States of America

William J Bowhers