Semiconductor integrated circuit and a burn-in method thereof

Abstract

A semiconductor integrated circuit includes a first circuit and a second circuit having a breakdown voltage higher than that of the first circuit. Operation voltages of the first and second circuits can be made equal to or different from each other. The second circuit has a level shift circuit for shifting the level of an output signal of the first circuit in accordance with an operation voltage of the second circuit, an external output buffer having an input that can receive, selectively, an output signal of the level shift circuit or an input signal that bypasses the level shift circuit. When the first and second circuits operate with a low voltage, bypass is selected. In high-voltage operation and burn-in, the level shift circuit is selected.

1 - 19 . (Cancelled)  
     
     
         20 . A burn-in method in a semiconductor integrated circuit that comprises a first circuit, and a second circuit having a breakdown voltage higher than a breakdown voltage of the first circuit, 
 the first circuit being operable at a first circuit operation voltage equal to or lower than a second circuit operation voltage of the second circuit,    the second circuit comprising a level shift circuit for shifting a level of an output signal of the first circuit in accordance with an operation voltage of the second circuit, an external output buffer, and first and second signal paths for alternately coupling an output of the first circuit to an input of the external output buffer, only the second of the first and second signal paths including the level shift circuit,    wherein the burn-in method comprises:    selecting the second signal path;    providing the first circuit operation voltage to the first circuit, and providing the second circuit operation voltage to the second circuit; and    operating the semiconductor integrated circuit in a burn-in state.    
     
     
         21 . A burn-in method according to  claim 20 , wherein the selecting is performed by a selection circuit operable to select either the first signal path or the second signal path and that selects the second signal path in the burn-in state.