Abstract: A differential sensing amplifier for content addressable memory is disclosed. In the differential sensing amplifier there is a detection circuit for detecting at an input node a change in an input signal comprising, a differential amplifier having a sense node and a reference node, a means for alternating the differential amplifier between a precharge phase and a sense phase, a precharge means for providing an input signal precharge voltage to the input signal via an input device, said input device selectively coupling the sense node to the input signal upon a change in the input signal, and a reference means for providing the reference node with a reference signal that continuously tracks the input precharge voltage during the precharge phase and actively maintains the input signal precharge voltage during the sense phase.

Abstract: A dynamic content addressable memory (CAM) cell is disclosed which is suitable for constructing relatively high-speed and large-capacity CAM arrays, having binary and ternary storage capability. The cell comprises a pair of storage devices, comparing means and a pair of memory access devices. In a compare operation, the comparing means couples a match line to a discharge line during a mismatch between a pair of complementary search bits carried on a pair of search lines and a pair of complementary data bits stored in the memory. In a read or write operation, the pair of access devices are activated by a word line to couple the storage capacitors to a pair of bit lines. A ‘0’ or a ‘1’ data bit is stored when the two storage capacitors carry complementary charges. A ‘don't care’ state is stored when both capacitors are discharged.

Abstract: A system and method for reduction of power consumed by a searchline buffer and control circuit during a CAM search-and-compare operation. The data buffer circuit samples one bit of a search word and a mask bit for driving a pair of complementary searchlines with the appropriate logic levels. The complementary searchlines are precharged to a mid-point voltage level between the high logic level voltage and the low logic level voltage during a precharge phase. The mid-point voltage level is applied on each searchline by sharing charge from the searchline at the high logic level voltage with the searchline at the low logic level voltage. Additional control logic compares the searchline data of the current search-and-compare operation with the next search-and-compare operation, to inhibit searchline precharging when both searchline data are at the same logic level.

Abstract: The invention detects multiple matches between search and stored data in high-density content addressable memories. An input signal is derived from the matchlines, such that the input signal starts discharging form a predetermined precharge level towards a discharge level determined by the number of match conditions. A reference signal is generated such that it starts to discharge at the same time from the same precharge level towards a reference level which falls between the two discharge levels corresponding to single and double match condition. A latching differential amplifier is activated shortly thereafter to compare the input signal with the reference signal and thereby provide an indication whether a multiple single or no match occurs on the matchlines, after which the amplifier is deactivated. The disclosed circuit features a relatively fast detection with low current consumption.

Abstract: A dynamic content addressable memory (CAM) cell is disclosed which is suitable for constructing relatively high-speed and large-capacity CAM arrays, having binary and ternary storage capability. The cell comprises a pair of storage devices, comparing means and a pair of memory access devices. In a compare operation, the comparing means couples a match line to a discharge line during a mismatch between a pair of complementary search bits carried on a pair of search lines and a pair of complementary data bits stored in the memory. In a read or write operation, the pair of access devices are activated by a word line to couple the storage capacitors to a pair of bit lines. A ‘0’ or a ‘1’ data bit is stored when the two storage capacitors carry complementary charges. A ‘don't care’ state is stored when both capacitors are discharged.

Abstract: The invention detects multiple matches between search and stored data in high-density content addressable memories. An input signal is derived from the matchlines, such that the input signal starts discharging form a predetermined precharge level towards a discharge level determined by the number of match conditions. A reference signal is generated such that it starts to discharge at the same time from the same precharge level towards a reference level which falls between the two discharge levels corresponding to single and double match condition. A latching differential amplifier is activated shortly thereafter to compare the input signal with the reference signal and thereby provide an indication whether a multiple single or no match occurs on the matchlines, after which the amplifier is deactivated. The disclosed circuit features a relatively fast detection with low current consumption.