Michael Bucher

A 4.3 GB/s Mobile Memory Interface With Power-Efficient Bandwidth Scaling

This paper presents a 4.3 GB/s mobile memory interface that utilizes low power states with rapid transition times to support power efficient signaling over a wide range of effective bandwidths. The fastest power state transition is implemented by a global synchronous clock pause that gates dynamic power consumption without any loss of system state. Extensive use of CMOS circuit topologies, with low static power consumption, provides maximum power savings when the clocks are paused. The memory controller forwards a half bit-rate clock to the memory for synchronous communication, which is similarly paused in the low power state. Thus, dynamic interface power on the memory itself naturally responds to the clock pausing, without any explicit communication from the controller or special low-power state on the memory. Low-swing differential signaling based on a push-pull voltage mode driver results in good signal integrity and power efficiency at peak activity. Test-chips fabricated in a 40 nm low-power CMOS technology achieve 3.3 mW/Gb/s power efficiency at 4.3 GB/s data bandwidth, and support better than 5 mW/Gb/s operation over a range from 0.03 to 4.3 GB/s.

A 5 Gb/s Link With Matched Source Synchronous and Common-Mode Clocking Techniques

A 5 Gb/s source-synchronous signaling system was developed utilizing a new clock/data skew minimization technique. The method incorporates a transmit clock delay line and integrating receiver yielding an increased tolerance to high frequency transmit source jitter. The system has the potential to support rapid turn-on without the clock buffer latency of conventional source-synchronous systems. A second method to minimize clock distribution delays with embedded clocking via superposition of clock in the common-mode across two differential pairs was also explored. A test device was fabricated in TSMCs 40 nm LP CMOS process and performance measurements indicate substantial margin improvements, even when the matched source-synchronous system is subjected to realistic source SJ and independent PSIJ noise. Comparable performance was also achieved with embedded common-mode clocking with matched peak swings, indicating it as a potential solution for pin-constrained designs.

Characterization of a low-power 6.4 Gbps DDR DIMM memory interface system

A memory system that meets the bandwidth, power efficiency, and capacity needs of future computing systems is presented in this paper. A 6.4 Gbps single-ended DDR memory interface for the controller and the DRAM was designed in a 28-nm CMOS process for a main memory system with dual-rank DIMMs. The architecture features a novel clocking scheme, per-pin timing adjustment, dynamic point-to-point signaling topology, and near ground signaling. The system V-T budget simulations and the characterization results of the fabricated memory interface are presented.

A 5Gb/s link with clock edge matching and embedded common mode clock for low power interfaces

A 5Gb/s signaling system was designed and fabricated in TSMCs 40nm LP CMOS process. A new clock/data skew minimization technique with a source-synchronous transmit clock delay line and integrating receiver tolerates high frequency transmit clock jitter and supports rapid turn-on without the clock buffer latency of conventional source-synchronous systems. A second method to minimize clock distribution via embedded clocking with superposition of clock in the common-mode was also explored.