A 100 MHz 0.41 fJ/(Bit∙Search) 28 nm CMOS-Bulk Content Addressable Memory for HEP Experiments

This paper presents a transistor-level design with extensive experimental validation of a Content Addressable Memory (CAM), based on an eXclusive OR (XOR) single-bit cell. This design exploits a dedicated architecture and a fully custom approach (both in the schematic and the layout phase), in order to achieve very low-power and high-speed performances. The proposed architecture does not require an internal clock or pre-charge phase, which usually increase the power request and slow down data searches. On the other hand, the dedicated solutions are exploited in order to minimize parasitic layout-induced capacitances in the single-bit cell, further reducing the power consumption. The prototype device, named CAM-28CB, is integrated in the deeply downscaled 28 nm Complementary Metal-Oxide-Semiconductor (CMOS) Bulk (28CB) technology. In this way, the high transistor transition frequency and the intrinsic lower parasitic capacitances allow the system speed to be improved. Furthermore, the high radiation hardness of this technology node (up to 1Grad TID), together with the CAM-28CB high-speed and low-power performances, makes this device suitable for High-Energy Physics experiments, such as ATLAS (A Toroidal LHC ApparatuS) at Large Hadron Collider (LHC). The prototype operates at a frequency of up to 100 MHz and consumes 46.86 µW. The total area occupancy is 1702 µm2 for 1.152 kb memory bit cells. The device operates with a single supply voltage of 1 V and achieves 0.41 fJ/bit/search Figure-of-Merit.