Highly testable design of BiCMOS logic circuits |
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Authors: | Osman M.Y. Elmasry M.I. |
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Affiliation: | VLSI Res. Group, Waterloo Univ., Ont.; |
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Abstract: | Most of the work reported in the literature to date on the testability of BiCMOS circuits has concentrated on fault characterization and the need for a suitable testing method that can address the peculiarities of BiCMOS circuits. The problem of adequately testing large BiCMOS logic networks remains open and complex. In this paper, we introduce a new design for testability technique for BiCMOS logic gates that results in highly testable BiCMOS logic circuits. The proposed design incorporates two features: a test charge/discharge path and built-in current sensing (BICS). The test charge/discharge path is activated only during testing and facilitates the testing of stuck-open faults using single test vectors. BICS facilitates testing of faults that cause excessive IDDQ. HSPICE simulation results show that the proposed design can detect stuck-open faults at a test speed of 10 MHz. Faults causing excessive IDDQ are detected by BICS with a detection time of 1 ns and a settling time of 2 ns. Impact of the proposed design on normal operation is minimal. The increase in propagation delay in normal operation is less than 3%. This compares very favorably with CMOS BICS reported in the literature, where the propagation delay increase was 20%, 14.4% respectively. The increase in the area is less than 15% |
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