1-2hit |
Satoru HANZAWA Hiromasa NODA Takeshi SAKATA Osamu NAGASHIMA Sadayuki MORITA Masanori ISODA Michiyo SUZUKI Sadayuki OHKUMA Kyoko MURAKAMI
A hierarchical timing adjuster that operates with intermittent adjustment has been developed for use in low-power DDR SDRAMs. Intermittent adjustment reduces power consumption in both coarse- and fine-delay circuits. Furthermore, the current-controlled fine-tuning of delay is free of short-circuit current and achieves a resolution of about 0.1 ns. In a design with 0.16-µm node technology, these techniques make the hierarchical timing adjuster able to reduce the operating current to 4.8 mA, which is 20% for the value in a conventional scheme with every-cycle measurement. The proposed timing adjuster achieves a three-cycle lock-in and only generates an internal clock pulse that has coarse resolution in the second cycle. The circuit operates over the range from 60 to 150 MHz, and occupies 0.29 mm2.
Koichiro ISHIBASHI Kunihiro KOMIYAJI Sadayuki MORITA Toshiro AOTO Shuji IKEDA Kyoichiro ASAYAMA Atsuyosi KOIKE Toshiaki YAMANAKA Naotaka HASHIMOTO Haruhito IIDA Fumio KOJIMA Koichi MOTOHASHI Katsuro SASAKI
A 16-Mb CMOS SRAM using 0.4-µm CMOS technology has been developed. This SRAM features common-centroid-geometry (CCG) layout sense amplifiers which shorten the access time by 2.4 ns. A flexible redundancy technique achieves high efficiency without any access penalty. A memory cell with stacked capacitors is fabricated for high soft-error immunity. A 16-Mb SRAM with a chip size of 215 mm2 is fabricated and an address access time of 12.5 ns has been achieved.