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Propagation Delay Measurement Accuracy Improvement Method For LSI Testers

IP.com Disclosure Number: IPCOM000102007D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 3 page(s) / 84K

Publishing Venue

IBM

Related People

Snyder, SC: AUTHOR

Abstract

Measurement of propagation delays of product modules on LSI testers are required to satisfy performance specifications. Typically the required propagation delay measurement accuracy is beyond what the LSI tester can provide. This problem is solved through the use of standards devices and an LSI tester software calibration.

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Propagation Delay Measurement Accuracy Improvement Method For LSI Testers

       Measurement of propagation delays of product modules on
LSI testers are required to satisfy performance specifications.
Typically the required propagation delay measurement accuracy is
beyond what the LSI tester can provide.  This problem is solved
through the use of standards devices and an LSI tester software
calibration.

      Measurement Defined.  A typical propagation delay example is
shown for an inverting path (see Fig. 1).

      The environment in which we are testing the product devices is
that of a production tester.  The device is placed in a socket which
is wired to an interface board (Fig. 2).  The appropriate signal
lines are routed to various measurement units and stimuli.  We are
interested in correcting for the error generated by the delay from
the tester drivers and tester comparators.

      Theory of Calibration.  To understand how the calibration table
is derived, we will look at a single path, the inverter.  First we
define some variables:
VARIABLE  DEFINITION
DS        Delay as measured on oscilloscope
DT        Delay as measured by tester
S         Skew used to correct tester measurements.  S is
   obtained by:
           S = DT - DS

      We can calibrate the tester by subtracting S from future tester
measurements to repeat what would of been measured by an external
oscilloscope (Fig. 2).  This method works given that the skew is
constant over a period of several days for this particular test and
this particular device under test.

      CALIBRATION METHOD Standards Module Generation.  An
oscilloscope is attached as diagrammed in...