Force Only Device Testing
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
A technique is reported for testing CMOS semiconductor devices at true device rates in a impedance-controlled environment favorable to the test system and which eliminates on-chip switching transients. Off-chip-driver (OCD) switching during chip testing may simultaneously cause switching transients on chip, a problem associated with large pinout VLSI N/CMOS and bipolar devices during chip testing. By inhibiting OCD switching during functional testing, transient switching problems are eliminated. Through the utilization of a comparator circuit on all OCDs, as shown in the figure, only forced data from a tester is used to functionally test a chip. Each OCD is disabled through a control pin 10 which places OCD 11 into a high impedance state (tri-state) during a test.