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Design and Self-Test for Switched-Current Building Blocks
Summer 1996 (vol. 13 no. 2)
pp. 10-17

Switched-current designs are receiving increasing interest within the VLSI community as the technique allowing analogue functions to be implemented on a digital process. In addition, switched-current designs tend to be robust and compatible with the trend for reduced supply voltages. This article describes the design of a novel type of switched-current memory cell with a built-in-self-test option. The cell is digitally controlled and can be used as a building block for a range of analogue functions. A divide-by-two circuit for reference signal generation in algorithmic A-to-D converters is given as an example application.

Furthermore, two self-test approaches for these building blocks are described and their effectiveness evaluated. Over 3000 single faults have been simulated in HSPICE to obtain the fault coverage using an open/short fault model. The self-test functions are easy to apply, need only a very small overhead and result in fault coverages up to 95% for shorts and 60% for open-circuits.

The analysis of undetected faults revealed that certain circuit structures used in the demonstrators which are common to analogue and mixed-signal designs are practically untestable.

Index Terms:
Switched-Current (SI) Design, Built-In Self-Test, BIST, Design-for-Testability, DfT, Fault Simulation, Testability
Thomas Olbrich, Andrew Richardson, "Design and Self-Test for Switched-Current Building Blocks," IEEE Design & Test of Computers, vol. 13, no. 2, pp. 10-17, Summer 1996, doi:10.1109/54.500196
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