Improvement for low power high performance hybrid type CAM

Match‐line control unit for power and delay reduction in hybrid CAM

“…But the proposed CAM quickly charges up to full V DD level; therefore, it causes charging overhead of V tn and 2V tn compared to the referred CAMs. Out of these factors, (i) and (iii) cause higher total power in the proposed design than the previous designs [17, 18] even though the delay is much reduced.…”

“…Search operations of the CAMs are checked under supply voltage scaling to determine delay and energy parameters. Existing hybrid designs, namely HT‐CAM [17] and IH‐CAM [18], operate well between moderate and high supply (0.9–1.2 V). But the ML delay (search speed) of HT and IH designs is worsened in low supply, and these CAMs cease to operate below 0.8 V, as shown in Figure 5a.…”

“…To quickly restore the precharged levels, and also to further decrease delay at the output (ML Out ), the proposed MLCU is designed with additional charging transistors and a fast discharging path (Figure 3). Despite low match delay at the output, there is overhead in search power (during evaluation) for some cases of R due to the following factors: (i) Whenever NAND‐ML is matched, more number of transistors urnt active in the NAND section of the proposed CAM compared to the existing hybrid CAMs [17, 18]; (ii) In the case of mismatch at both ML sections, HT [17] and IH [18] have only one charging path of output in their interface logic circuits. However, the proposed design has two different charging paths in MLCU; and (iii) In case of match at the NAND section and mismatch at the NOR section, HT and IH CAMs charge up their outputs to V DD ‐V tn (where V tn is threshold of nMOS) and V DD ‐2V tn , respectively.…”

“…This leads ML capacitance to charge and discharge frequently, dissipating more dynamic power. Existing hybrid MLs [17, 18] and proposed ML based on R = 2 segmentation dissipate more power over their corresponding R ≥ 4 segmentations. The dissipation in all hybrid CAMs decreases further as ‘R’ is raised from 4 to 10.…”

“…Since the proposed design forms a CAM word with 2 ML partitions (NAND & NOR), we focus on works with segmentation schemes [13–15, 27] and hybrid MLs [16–19, 22, 28]. In SMA‐CAM [13], a match‐line row is segmented into two sets of precharge section and charge‐shared section.…”