Forced substrate test mode for packaged integrated circuits

Abstract

An integrated circuit such as an SRAM or DRAM fabricated in a package having a number of external pins includes a plurality of inputs and outputs electrically coupled to the external package pins, an internal substrate that is unconnected to any of the external pins, a test mode indicator circuit having an input coupled to an external pin and an output for providing a test mode signal and a switch responsive to the test mode signal for coupling the substrate to a predetermined voltage. The predetermined voltage can either be ground, or a negative voltage introduced on a pin that is normally set to a logic zero during package level testing. The test mode signal can also be used to disable the on-chip charge pump. The test mode indicator circuit can include a super voltage indicator, an electronic key, or latch circuit in order to receive the test mode indication signal on an existing package pin.

Dependencies are inferred from the claim text.