| 摘要 |
A content addressable memory (CAM) includes a voltage power supply input and an enable input. An enable control circuit is connected to the enable input, and operates to compare an external voltage to an enable reference voltage. If the external voltage drops below the enable reference voltage, the enable control circuit drives the enable input to place the CAM into a low current, stand-by mode of operation. A voltage supply back-up circuit is connected to the voltage power supply input, and operates to compare the external voltage to a supply reference voltage. If the external voltage drops below the supply reference voltage, the voltage supply back-up circuit switches the voltage power supply input for the CAM from the external voltage input to a battery backup. As an alternative, the voltage power supply input for the CAM includes a separate power input for a CAM array, and the switch causes only that separate power input for the CAM array to be powered from the battery back-up. The foregoing circuits are fabricated on an integrated circuit chip with the CAM. Alternatively, the CAM and the circuit may be fabricated on separate chips that share a common package.
|
