Methods And Apparatus For Testing Electronic Circuits

Abstract

Methods and apparatus are provided for testing to determine the existence of defects and faults in circuits, devices, and systems such as digital integrated circuits, SRAM memory, mixed signal circuits, and the like. In particular, methods and apparatus are provided for detecting faults in circuits, devices, and systems using input control signals to generate controlled-duration, controlled pulse-width, transient power supply currents in a device under test, where said transient power supply currents are of controllable bandwidth and can be used as observables to determine faulty or defective operation. Additionally, methods and apparatus are provided to permit high bandwidth sensing of transient supply currents as need to preserve the narrow widths of these current pulses. These methods may include autozero techniques to remove supply current leakage current and DC offsets associated with practical current sensing currents. The sensed transient supply currents can be compared to single or multiple thresholds to assess normal or faulty or defective operation of the device under test.

1 . An apparatus for determining defects and faults in electronic devices having at least one input that is coupled between a power supply and a ground to receive a supply current therefrom, the apparatus comprising:
 a current sensor electrically coupled between the power supply and a device under test, the device under test comprising an SRAM device, and the current sensor comprising:
 at least one input electrically coupled to the power supply; 
 a first output electrically coupled to the device under test and capable of supplying a supply current voltage to the device; and 
 a second output capable of delivering a signal proportional to the supply current delivered to the device under test. 
   
   
   
       2 . An apparatus for determining defects and faults in electronic devices having at least one input that is coupled between a power supply and a ground to receive a supply current therefrom, the apparatus comprising:
 a resistor electrically coupled between the power supply and a device under, the resistor comprising:
 at least one input electrically coupled to the power supply; 
 a first output electrically coupled to the device under test and capable of supplying a supply current voltage to the device under test; and 
 a second output capable of delivering a signal proportional to the supply current delivered to the device under test. 
   
   
   
       3 . A method for determining faults or defects in an electronic device that is coupled between a power supply and a ground to receive supply current therefrom while the device is in operation, the method comprising:
 exposing a fault-free device to a plurality of pairs of complementary control signal vectors;   generating a plurality of complementary pairs of baseline transient supply currents associated with the signal vectors;   exposing the device under test to one or more of the complementary pairs of vectors;   measuring the transient supply currents generated;   comparing the generated transient supply currents to the baselines currents; and   determining if the generated transient supply currents are within a normal circuit variation of the baseline transient currents.   
   
   
       4 . The method of  claim 3 , further comprising:
 calculating a baseline difference for each complementary pair of baseline transient currents;   calculating a test difference for each complementary pair of generated transient currents; and   comparing the baseline differences to the corresponding test differences.