Patent Application
20090287971
1. Field of the Invention
The present invention relates generally to memory device testing and in particular to AC testability path for memory devices.
2. Background Information
AC testability is an important part of memory chip verification. Standard chip verification (or bring up) involves running various patterns on LBIST (Logic Built in Self Test) and ABIST (Array Built in Self Test) paths. Ideally, LBIST and ABIST paths should be mutually exclusive and have no interaction with each other. However, this is very rarely achieved in practice and in most cases LBIST paths are dependent on the timing and behavior of a memory array which is typically tested by ABIST.
A method and apparatus for testing a random access memory device is provided. One embodiment involves providing an interface between Logic Built in Self Test (LBIST) and Array Built in Self Test (ABIST) paths for memory testing, including providing a cross-coupled flash memory such as a NAND device with an LBIST test path; configuring the cross-coupled NAND device for interfacing ABIST and LBIST paths by modeling a worst case scenario for timing from a domino read static random access memory (SRAM) array; and modifying data in the cross-coupled NAND device using an LBIST controlled data path at essentially the latest point in time when a read may propagate from the array to provide full AC test coverage of down stream logic.
Other aspects and advantages of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention.
For a fuller understanding of the nature and advantages of the invention, as well as a preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings, in which:
The following description is made for the purpose of illustrating the general principles of the invention and is not meant to limit the inventive concepts claimed herein. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations. Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc.
A method and apparatus for testing a random access memory device is provided. One embodiment involves providing an interface between Logic Built in Self Test (LBIST) and Array Built in Self Test (ABIST) paths for memory testing, including providing a cross-coupled NAND device with an LBIST test path; configuring the cross-coupled NAND device for interfacing ABIST and LBIST paths by modeling a worst case scenario for timing from a domino read static random access memory (SRAM) array; and modifying data in the cross-coupled NAND device using an LBIST controlled data path at essentially the latest point in time when a read may propagate from the array to provide full AC test coverage of down stream logic.
An example implementation comprises a cross-coupled NAND circuit with AC testability path for memory devices. The circuit functions as an interface between LBIST and ABIST paths, providing an interface between LBIST and ABIST test domains that improve memory chip manufacturing and quality. An example cross-coupled NAND structure with an LBIST test path that models a worst case scenario for the timing from a domino read SRAM is described below. The circuit allows realistic testing of combined ABIST and LBIST paths by modeling a worst case read from a domino read SRAM, which is important since domino read SRAM have variable access times. The invention models a worst case read by modifying the data in the cross coupled NAND device through an LBIST controlled data path at the latest point in time where a read may actually propagate out of the SPAM memory array. By performing the modification in the cross-coupled NAND, it is possible to propagate realistic timing to down stream logic during LBIST to provide full AC test coverage.
As is known to those skilled in the art, the aforementioned example embodiments described above, according to the present invention, can be implemented in many ways, such as program instructions for execution by a processor, as software modules, as computer program product on computer readable media, as logic circuits, as silicon wafers, as integrated circuits, as application specific integrated circuits, as firmware, etc. Though the present invention has been described with reference to certain versions thereof; however, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.
Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiments can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.
