Integrated circuit with internal semiconductor supply switch - allowing internal gates to be tested even when circuit is operating

摘要

The integrated circuit has its individual circuit elements, such as logic gates, testable even when the IC is connected to other ICs in a complete circuit, i.e. in a composite LSI chip. This is particularly useful in complex ICs. The IC's internal logic gates are connected to one supply voltage rail and, over an internal semiconductor switch (T1) to the other supply rail (Us). The switch's control electrode is connected to an external terminal to which a switching signal (SH) is applied to disconnect the supply from the gates. In normal operating conditions the supply voltage is switched through.