Increasing test accuracy by varying driver slew rate

A variable slew rate, together with the ability to control ascending and descending slew rates independently, significantly improves the overall accuracy of test and verification systems for application-specific ICs. Although a high slew rate is usually desirable, in some cases, such as ECL devices and devices in circuits of older vintage, a variable rate is advantageous. Essential driver characteristics are identified, and the driver model is described. For a small parts cost, and with only a negligible increase in power requirements, it is estimated that independent control of slew rates for ascending and descending edges can improve tester accuracy by several hundred picoseconds.<>