Method and apparatus for applying and monitoring programmed test signals during automated testing of electronic circuits

• US 4,646,299 A
• Filed: 05/17/1984
• Issued: 02/24/1987
• Est. Priority Date: 08/01/1983
• Status: Expired due to Fees

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Murdock, James R., Schinabeck, John
• Primary Examiner(s): ATKINSON, CHARLES
• Application Number:
  US06/611,445
• Time in Patent Office: 1,013 Days
• Field of Search: 371/20, 371/25, 371/27, 324/73 R, 324/73 AT, 324/73 PC, 364/579, 364/580
• US Class Current: 714/736
• CPC Class Codes: G01R 31/31713 Input or output interfaces for test, e.g. test pins, buffers for scan test G01R31/318572
• CPC Class Codes: G01R 31/3191 Calibration
• CPC Class Codes: G01R 31/31922 Timing generation or clock distribution G01R31/3191 takes precedence
• CPC Class Codes: G01R 31/31926 Routing signals to or from the device under test [DUT], e.g. switch matrix, pin multiplexing
• CPC Class Codes: G01R 31/31928 Formatter driver, receiver details G01R31/31924
• CPC Class Codes: G01R 31/31935 Storing data, e.g. failure memory
• CPC Class Codes: G01R 31/31937 Timing aspects, e.g. measuring propagation delay G01R31/3191 and G01R31/31922 take precedence; marginal testing G06F11/24
• CPC Class Codes: H03K 2005/00247 using counters
• CPC Class Codes: H03K 2005/00254 using microprocessors
• CPC Class Codes: H03K 2005/0026 using memories or FIFO's
• CPC Class Codes: H03K 5/131 Digitally controlled
• CPC Class Codes: H03K 5/14 by the use of delay lines H03K5/133 takes precedence

Abstract

A plurality of test signal applying and monitoring circuits are coupled to pins of an electronic device being tested to force test stimuli signals onto input pins of the device under test. The response signals are monitored while the device is being tested. Each test signal applying and monitoring circuit includes a node to be coupled to a pin of the device under test, a digitally programmed source for supplying a test signal connectable to the node by a first switch, and a comparison circuit connected to the node by a second switch for indicating the relative amplitude of the response signal with respect to a programmed reference level. The digitally programmed source is included for providing gated voltage-current crossover forcing functions during functional testing to minimize the disturbance when the device being tested is connected and to protect out of tolerance devices. Programmable voltage and current values define a pass window to assure a non-ambiguous go/no-go result during testing. Other features are also disclosed.

Claims

1. A method for applying and monitoring a test signal at a node of a device under test including digitally programmed source means having a preselected programmed voltage-current characteristic defined by not-to-exceed voltage rail and current rail levels switchably connected by a first switch means to the node for supplying a test signal to the node and comparison means switchably connected by a second switch means to the node, the method comprising the steps of:

connecting the test signal to the node;

comparing the test signal with a preselected programmed reference level;

providing an indication of the relative magnitude of the test signal with respect to the preselected programmed reference level; and

providing a preselected programmed constant signal in the event that the test signal has a predetermined relationship with respect to the programmed reference level.

2. The method of claim 1 wherein the test signal is a forcing function which starts at zero volts and one percent of the maximum current of a preselected voltage-current range.

3. The method of claim 1 wherein the step of comparing the test signal with a preselected programmed reference level comprises comparing the voltage applied to the node with the preselected programmed voltage rail level, the step of providing an indication of the relative magnitude of the test signal with respect to the preselected programmed reference level comprises providing an indication of the relative magnitude of the voltage applied to the node with respect to the voltage rail level, and the step of providing a preselected programmed constant signal in the event that the test signal has a predetermined relationship with respect to the preselected programmed reference level comprises applying the preselected programmed current rail level when the voltage applied to the node reaches the voltage rail level.

4. The method of claim 3 wherein the test signal is a forcing function which starts at zero volts and one percent of the maximum current of a preselected voltage-current range.

5. The method of claim 1 wherein the step of comparing the test signal with a preselected programmed reference level comprises comparing the current at the node with the preselected programmed current rail level, the step of providing an indication of the relative magnitude of the test signal with respect to the preselected programmed reference level comprises providing an indication of the relative magnitude of the current at the node with respect to the current rail level, and the step of providing a preselected programmed constant signal in the event that the test signal has a predetermined relationship with respect to the preselected programmed reference level comprises applying the preselected programmed voltage rail level when the current at the node reaches the current rail level.

6. The method of claim 5 wherein the test signal is a forcing function which starts at zero volts and one percent of the maximum current of a preselected voltage-current range.

7. Apparatus for applying and monitoring a test signal at a node of a device under test, comprising:

digitally programmed source means switchably connected by a first switch means to the node, the digitally programmed source means having a preselected programmed voltage-current characteristic defined by not-to-exceed voltage rail and current rail levels for supplying test signals and alternatively a preselected programmed constant signal to the node; and

comparison means connected to the digitally programmed source means and switchably connected by a second switch means to the node for indicating the relative magnitude of the test signal with respect to a preselected programmed reference level;

the digitally programmed source means supplying the test signals unless the test signal applied has a predetermined relationship with respect to the preselected programmed reference level;

the digitally programmed source means supplying the preselected programmed constant signal in the event that the applied test signal has a predetermined relationship with respect to the preselected programmed reference level.

8. Apparatus as in claim 7 wherein the digitally programmed source means is a crossover source which supplies a test signal in the form of a forcing function that starts at zero volts and one percent of the maximum current of a preselected voltage-current range.

9. Apparatus as in claim 7 wherein the comparison means compares the voltage applied to the node with the preselected programmed voltage rail level for providing an indication of the relative magnitude of the voltage applied to the node with respect to the voltage rail level;

the digitally programmed source means supplying the test signals unless the voltage applied to the node reaches the voltage rail level;

the digitally programmed source means supplying the preselected programmed current rail level when the voltage applied to the node reaches the voltage rail level.

10. Apparatus as in claim 9 wherein the digitally programmed source means is a crossover source which supplies a test signal in the form of a forcing function that starts at zero volts and one percent of the maximum current of a preselected voltage-current range.

11. Apparatus as in claim 7 wherein the comparison means compares the current at the node with the preselected programmed current rail level for providing an indication of the relative magnitude of the current at the node with respect to the current rail level;

the digitally programmed source means supplying the test signals unless the current at the node reaches the current rail level;

the digitally programmed source means supplying the preselected programmed voltage rail level when the current at the node reaches the current rail level.

12. Apparatus as in claim 11 wherein the digitally programmed source means is a crossover source which supplies a test signal in the form of a forcing function that starts at zero volts and one percent of the maximum current of a preselected voltage-current range.

13. Apparatus as in claim 7 wherein the switch means are controlled by a computer means.

14. Apparatus as in claim 13 wherein the switch means comprise reed relays.

15. Apparatus as in claim 14 wherein the computer means comprises a test head controller.

16. Apparatus as in claim 7 wherein the digitally programmed source means is a crossover source.

17. Apparatus as in claim 16 wherein the digitally programmed source means supplies a test signal which is a forcing function that starts at zero volts and one percent of the maximum current of a preselected voltage-current range.

18. A method for monitoring the response signal at a node of a device under test caused by a test signal applied to the node by digitally programmed source means having a preselected programmed voltage-current characteristic defined by not-to-exceed voltage rail and current rail levels switchably connected by a first switch means to the node and comparison means switchably connected by a second switch means to the node, the method comprising the steps of:

connecting the test signal to the node;

comparing the response signal voltage at the node with a first preselected programmed voltage level;

comparing the response signal voltage at the node with a second preselected programmed voltage level;

comparing the response signal current at the node with a first preselected programmed current level;

comparing the response signal current at the node with a second preselected programmed current level;

providing an indication of the relative amplitude of the response signal voltage and current with respect to the first and second preselected programmed voltage levels and first and second preselected programmed current levels, respectively;

providing a pass signal when the response signal voltage and current have a first predetermined relationship with respect to the first and second preselected programmed voltage levels and first and second preselected programmed current levels, respectively; and

providing a fail signal when the response signal voltage and current have a second predetermined relationship with respect to the first and second preselected programmed voltage levels and first and second preselected programmed current levels, respectively;

thereby providing a non-ambiguous pass/fail result.

19. The method of claim 18 wherein the test signal is a forcing function which starts at zero volts and one percent of the maximum current of a preselected voltage-current range.

20. Apparatus for monitoring the response signal at a node of a device under test caused by a test signal applied to the node, comprising:

digitally programmed source means switchably connected by a first switch means to the node, the digitally programmed source means having a preselected programmed voltage-current characteristic defined by not-to-exceed voltage rail and current rail levels for supplying test signals to the node;

first comparison means switchably connected by a second switch means to the node for indicating the relative amplitude of the response signal voltage at the node with respect to a first preselected programmed voltage level;

second comparison means switchably connected by the second switch means to the node for indicating the relative amplitude of the response signal voltage at the node with respect to a second preselected programmed voltage level;

third comparison means switchably connected by the second switch means to the node for indicating the relative amplitude of the response signal current at the node with respect to a first preselected programmed current level;

fourth comparison means switchably connected by the second switch means to the node for indicating the relative amplitude of the response signal current at the node with respect to a second preselected programmed current level;

means connected to the comparison means for providing a pass signal when the response signal voltage and current have a first predetermined relationship with respect to the first and second preselected programmed voltage levels and first and second preselected programmed current levels, respectively; and

means connected to the comparison means for providing a fail signal when the response signal voltage and current have a second predetermined relationship with respect to the first and second preselected programmed voltage levels and first and second preselected programmed current levels, respectively;

whereby a non-ambiguous pass/fail result is provided.

21. Apparatus as in claim 20 wherein the digitally programmed source means is a crossover source which supplies a test signal in the form of a forcing function that starts at zero volts and one percent of the maximum current of a preselected voltage-current range.