Quantifying circuit performance

• US 5,878,383 A
• Filed: 10/29/1996
• Issued: 03/02/1999
• Est. Priority Date: 10/29/1996
• Status: Expired due to Fees

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Carter, Malcolm Edward
• Primary Examiner(s): Shah, Kamanini
• Application Number:
  US08/739,358
• Time in Patent Office: 854 Days
• Field of Search: 364/551.01, 364/571.03, 364/550, 364/571.02, 371/28, 371/25.1, 309/58, 702/182, 702/99
• US Class Current: 702/182
• CPC Class Codes: G01R 31/2849 Environmental or reliability testing, e.g. burn-in or validation tests of individual semiconductors G01R31/2642; of printed circuits boards G01R31/2817; of IC's G01R31/2855
• CPC Class Codes: G06F 11/24 Marginal checking or other specified testing methods not covered by G06F11/26, e.g. race tests
• CPC Class Codes: H04L 43/50 Testing arrangements
• CPC Class Codes: H04M 3/22 Arrangements for supervision, monitoring or testing

Abstract

The invention relates to automated testing of equipment items of the electronic, electrical, and optical type over a range of environmental conditions. A testing apparatus operates to vary an operating environment of an item of test equipment between a lower extreme and an upper extreme, and iteratively searches each test parameter for a peak response. The peak response is compared with a response limit specified in a customer specification or an international standard. The apparatus assesses a design robustness of the equipment item by comparing a set of measured responses with a maximum range of responses specified in the customer specification or international standard. The apparatus produces a data output for each performance parameter tested, identifying performance parameters which are outside the customer specification, or which have insufficient design robustness.

Claims

1. A method of determining whether a performance characteristic of an item of equipment is within a specified performance limit, comprising the steps of:

setting a performance limit data corresponding to said specified performance limit;

obtaining performance data corresponding to a performance characteristic of the equipment at an extremity of a predetermined range of environmental conditions, said equipment maintained within a predetermined set of environmental conditions;

iteratively searching said performance data for a peak performance value data within said predetermined range of environmental conditions; and

comparing said peak performance value data with said performance limit data to determine whether a peak performance value represented by said peak performance value data is within said specified performance limit.

2. The method as claimed in claim 1, wherein said step of iteratively searching for a peak performance value data comprises analysing performance data obtained at a specified extreme environment condition and at an ambient environment condition, to estimate a new performance data at an environment condition between said extreme environment condition and said ambient environment condition.

3. The method as claimed in claim 2, wherein said step of iteratively searching for a peak performance value data comprises;

connecting said performance data obtained at ambient environmental conditions, and said performance data obtained at a first extreme environmental condition by a first function of performance data against environment condition, said first function having a first gradient;

obtaining a second function of performance data against environment condition said second function having a new gradient; and

selecting a position along said second linear function, said position representing an estimated peak performance value data.

4. The method as claimed in claim 3, wherein said step of iteratively searching for a peak performance value data comprises;

connecting by means of a third linear function, said performance data obtained at ambient environment condition with a performance data obtained at a second extreme environment condition;

extrapolating said third function at environmental conditions between said ambient and said first extreme environmental condition,

determining an intersection of said second linear function and said extrapolated third linear function, wherein said selected position corresponds to said intersection.

5. The method as claimed in claim 4, wherein a said function comprises a linear function.

6. The method as claimed in claim 3, wherein said step of obtaining a second function comprises selecting a said new gradient lying between said first gradient and a function of infinite gradient.

7. The method as claimed in claim 3 wherein said second function is selected by;

determining an angle between said first function and a function of infinite gradient;

multiplying said angle by a predetermined multiplication factor to obtain a new angle with respect to said function of infinite gradient; and

assigning said second function said new gradient corresponding to a function at said new angle.

8. A method of determining a performance characteristic of an item of equipment, said method comprising the steps of:

(i) placing the equipment item in a controllable environment;

(ii) maintaining the equipment at a first set of environmental conditions;

(iii) monitoring a performance of said equipment item at said first set of environmental conditions;

(iv) maintaining said equipment at a second set of environmental conditions;

(v) monitoring the performance of said equipment item at said second set of environmental conditions;

(vi) estimating a peak performance of said equipment item;

(vii) determining an environmental condition corresponding to a said estimated peak performance;

(viii) maintaining said equipment item at said environmental condition corresponding to said estimated peak performance; and

(ix) monitoring an actual performance of said equipment item at said environmental condition corresponding to said estimated peak performance.

10. The method as claimed in claim 8, wherein said step of estimating a peak performance of said equipment item comprises estimating a peak performance corresponding to an environment condition between said first and second sets of environment conditions.

11. The method as claimed in claim 8, wherein said step of determining an environmental condition corresponding to said estimated peak performance comprises searching for an environmental condition between said first set of environmental conditions and said second set of environmental conditions.

12. The method as claimed in claim 8, wherein a said step of monitoring a performance of said equipment item comprises:

inputting test signals to said equipment item; and

monitoring response signals produced by said equipment item in response to said test signals.

13. The method as claimed in claim 8, further comprising a step of setting a limit of performance, and comparing said estimated peak performance with said performance limit.

18. The apparatus as claimed in claim 10, which operates to carry out a series of performance tests relating to a plurality of different performance parameters, and

for each test said means for controlling an environment maintains said environment within one or more predetermined environmental conditions.

19. The apparatus as claimed in claim 11, which operates to carry out a series of performance tests relating to a plurality of different performance parameters, and for each test said means for controlling an environment maintains said environment within one or more predetermined environmental conditions.

9. The method as claimed in claim 9, wherein said step of estimating a peak performance of said equipment item comprises the steps of:

operating said equipment item at said first set of environmental conditions;

operating said equipment item at said second set of environmental conditions; and

operating said equipment item at a third set of environmental conditions between said first and second environmental conditions.

14. A method of processing performance data corresponding to a plurality of performance parameters of an item of equipment, comprising the steps of:

setting a performance limit data for each performance parameter;

for each performance parameter,

obtaining performance data at an ambient environmental condition;

obtaining performance data at a lower environmental condition;

obtaining performance data at an upper environmental condition;

comparing said obtained performance data with said performance limit data;

if said performance data exceeds said performance limit data, recording a fail test data;

if said performance data is within said performance limit data, estimating a peak performance data;

if said peak performance data is within said performance limit data, recording a pass test data;

if said peak performance data exceeds said performance limit data, obtaining an estimated environmental data corresponding to said estimated peak performance data;

obtaining a performance data at an environmental condition corresponding to said estimated environmental condition;

comparing said performance data at said estimated environmental condition with said performance limit data; and

if said performance data at said estimated environmental condition is within said performance limit data, recording a pass test data.

15. Apparatus for performance testing an item of equipment, said apparatus comprising:

means for controlling an environment;

test means for testing a set of performance parameters of said equipment item;

means for recording results of a set of said performance parameter tests implemented by said testing means; and

means for analysing said results of performance parameter tests;

wherein said test means operates to automatically implement a test routine to test said performance parameters at a lower environment condition, an upper environment condition, and an ambient environment condition between said upper and lower environment conditions, and said analysing means automatically analyses said test results to identify performance parameters which lay outside predefined specified performance limits.

16. The apparatus as claimed in claim 15, therein said means for controlling an environment is capable of changing said environment in response to a result of an analysis carried out by said analysing means.

17. Apparatus for determining whether a performance characteristic of an item of equipment is within a specified performance limit, comprising:

means for setting a performance limit data corresponding to said specified performance limit;

means for maintaining said equipment item within a predetermined set of environmental conditions;

means for obtaining performance data corresponding to a performance characteristic of the equipment at an extremity of a predetermined range of environmental conditions, said equipment maintained within a predetermined set of environmental conditions;

means for iteratively searching said performance data for a peak performance value data within said predetermined range of environmental conditions; and

means for comparing said peak performance value data with said performance limit data to determine whether a peak performance value represented by said peak performance value data is within said specified performance limit.