Kevin S. Donnelly

A portable digital DLL for high-speed CMOS interface circuits

A digital delay-locked loop (DLL) that achieves infinite phase range and 40-ps worst case phase resolution at 400 MHz was developed in a 3.3-V, 0.4-/spl mu/m standard CMOS process. The DLL uses dual delay lines with an end-of-cycle detector, phase blenders, and duty cycle correcting multiplexers. This more easily process portable DLL achieves jitter performance comparable to a more complex analog DLL when placed into identical high-speed interface circuits fabricated on the same test-chip die. At 400 MHz, the digital DLL provides <250 ps peak-to-peak long-term jitter at 3.3 V and operates down to 1.7 V, where it dissipates 60 mW. The DLL occupies 0.96 mm/sup 2/.

A 2.5 V CMOS delay-locked loop for 18 Mbit, 500 megabyte/s DRAM

This paper describes clock recovery circuits specifically designed for the hostile noise environment found aboard dynamic RAM chips. Instead of a phase-locked loop having a voltage-controlled oscillator, these circuits implement a delay-locked loop, thereby achieving low jitter and reduced sensitivity to noise on the substrate and the power supply rails. Differential signals are employed both in signal paths and in control paths, further decreasing noise sensitivity and simultaneously allowing operation from low voltage supplies. An unorthodox voltage controlled phase shifter, operating on the principle of quadrature mixing, yields a circuit with unlimited delay range (modulo 2/spl pi/ radians). Minor loops, enclosed within the overall loop feedback path, perform active duty cycle correction. Measured results show peak-to-peak jitter of 140 ps on the internal clock signal, and 250 ps on the external data pins, sufficiently small to allow 500 Megabyte/s transfer rates at the I/O interface. >

A 0.4-4-Gb/s CMOS quad transceiver cell using on-chip regulated dual-loop PLLs

This paper describes the design and implementation of a quad high-speed transceiver cell fabricated in 0.13-/spl mu/m CMOS technology. The clocking circuit of the cell employs a dual-loop architecture with a high-bandwidth core phase-locked loop (PLL) and low-bandwidth digitally controlled interpolators. To achieve low jitter while maintaining low power consumption, the dual-loop PLL uses two on-chip linear regulators of different bandwidths, one for the core and the other for the interpolator loop. The prototype chip operates from 400 Mb/s to 4 Gb/s with a bit error rate of <10/sup -14/. The quad cell consumes 390 mW at 2.5 Gb/s (95 mW/link) under typical operating conditions with a 400-mV output swing driving double terminated links.

A 660 MB/s interface megacell portable circuit in 0.3 /spl mu/m-0.7 /spl mu/m CMOS ASIC

A high-speed interface circuit delivering 660 MB/s data is implemented as a byte-wide I/O bus-interface cell. The interface contains low-swing input receivers, controlled-current output drivers, and clock-recovery circuits. The circuits perform well in noisy environments such as microprocessors, and withstand LdI/dt noise generated in high-inductance packages such as PQFPs. The interface is implemented as a full-custom ASIC library mega-cell, reducing area and power over gate-array approaches. An advanced CAD methodology is used to easily port the analog circuits and high-speed digital circuits in the interface cell to multiple-fabrication process technologies. The cell is used as an interface for ASIC-to-DRAM communication and for ASIC-to-ASIC communication, for point-to-point links and for bused links.

1.6 Gb/s/pin 4-PAM signaling and circuits for a multidrop bus

A 1.6 Gb/s/pin 4-PAM multi-drop signaling system has been implemented in 0.35-/spl mu/m CMOS. The system uses current-mode single-ended signaling, with three DC references shared across six I/O pins. A high-gain windowed integrating receiver with wide common-mode range was designed in order to improve SNR when operating with the smaller input overdrive of 4-PAM. Voltage and timing margins are measured via shmoos in a two-drop bussed system.

A 0.4-4 Gb/s CMOS quad transceiver cell using on-chip regulated dual-loop PLLs

A quad high-speed transceiver cell is designed and implemented in 0.13 /spl mu/m CMOS technology. To achieve low jitter while maintaining low power consumption, dual on-chip regulators are used for each dual-loop PLL. The prototype chip demonstrates that the links can operate from 400 Mb/s to 4 Gb/s with a bit error rate <10/sup -14/. The quad cell consumes 390 mW at 2.5 Gb/s (95 mW/link) under typical operating conditions with a 400 mV output swing driving double terminated links.

A 2.6-GByte/s multipurpose chip-to-chip interface

A 2.6 GByte/s megacell that interfaces to single or double byte wide DRAMs or logic chips is implemented using 0.35-0.18 /spl mu/m CMOS technologies. Special I/O circuits are used to guarantee 800 Mbit/s/pin data rate. Microwave PC board design methodologies are used to achieve the maximum possible interconnect bandwidth.

A multiple vendor 2.5-V DLL for 1.6-GB/s RDRAMs

A DLL design and porting methodology have been described to enable multiple vendors to create a 400 MHz DLL from a template design in a 0.25 /spl mu/m, 64 Mb DRAM process.

A portable digital DLL architecture for CMOS interface circuits

A digital DLL was developed which achieves infinite phase range and 40 ps worst-case phase resolution at 400 MHz. The architecture uses dual delay lines with an end-of-cycle detector, phase blenders, and duty cycle correctors. This more easily process-portable DLL achieves jitter performance comparable to a more complex analog DLL, when placed into identical high-speed interface circuits fabricated on the same die in a 0.4 /spl mu/m CMOS process.

Development of single-chip multi-GB/s DRAMs

Discusses improvement of current device jitter budget. A DRAM incorporating these improvements is expected to operate with 1.3Gb/s/pin signaling rate (650MHz clock rate) delivering 5.2GB/s from a 32b interface. Such a 64Mb density DRAM will exhibit a fill rate of 650times/s. Compared to an industry-standard 64M SDRAM operating at 66MHz with its 33times/s fill rate in a 2Mx32 organization, the ratio is 19.7:1.