US 7,609,079 B2 · Probeless DC testing of CMOS I/O circuits

Abstract

A method and implementation is described by which I/O input and output circuitry of a CMOS chip are measured without the need to probe the chip. Output driver transistors are used to provide marginal voltages to test input circuits, and the output driver transistors are segmented into portions where a first portion is used to provide a representative “on” current, which is coupled to a test bus that is further connected to a current comparator circuit contained within the chip. Both leakage and “on” current of the driver transistors is measured using segmented driver transistors. The output of the current comparator circuit is connected to a test scan register or to a test output from which test results are obtained digitally. The testing techniques are also applicable for other semiconductor devices.

Claims25

Dependent claims

A method of leakage testing a CMOS driver, comprising:

a) connecting a bias voltage to a driver portion of a CMOS chip output driver connected to an output pad of said chip;
b) controlling off said driver portion;
c) closing a switch circuit coupling said chip pad to a test bus;
d) coupling a leakage current from said driver portion to a current comparator connected to said test bus;
e) comparing said leakage current to a reference current in a current comparator;
f) coupling results of said current comparator to a test result output mechanism;
g) opening said switch circuit;
h) continuing to a next said output pad and step c) until said driver portion of all said output pads are tested, then disconnect said bias voltage;
and
i) continuing to said next said driver portion of the chip output drivers, connecting said bias voltage to the next driver portion and returning to step b) until all said next driver portions are tested, then end.

7 more elements

Dependencies are inferred from the claim text.

Probeless DC testing of CMOS I/O circuits

Life of this patent

Probeless DC testing of CMOS I/O circuits

Life of this patent

Abstract

Claims25