International Business Machines Corporation

University of Michigan

Jerry C Kao

Jente Benedict Kuang

Kevin John Nowka

Marios C Papaefthymiou

Visvesh S Sathe

Juang-Ying Chueh

Hung Cai Ngo

Gary Dale Carpenter

Fadi Hikmat Gebara

Alan J Drake

Liang-Teck Pang

Conrad H Ziesler

Salvatore Nicholas Storino

Jayakumaran Sivagnaname

Christophe Robert Tretz

Chung-Tao Li

Disclosed herein is a digital system that includes a distribution network having a path to carry a reference clock and an adjustable delay element disposed along the path, and first and second clock domains coupled to the distribution network to receive the reference clock and configured to be driven by respective clock waveforms, each of which has a frequency in common with the reference clock. The digital system further includes a phase detector coupled to the first and second clock domains to generate a phase difference signal based on the clock waveforms, and a control circuit coupled to the phase detector and configured to adjust the adjustable delay element based on the phase difference signal.

Clock distribution network architecture with clock skew management

A circular edge detector on an integrated circuit including a plurality of edge detector cells, each of the plurality of edge detector cells having an input select block operable to receive a data signal and a previous cell signal and to generate a present cell signal, and a state capture block operably connected to receive the present cell signal. The present cell signal of each of the plurality of edge detector cells is provided to a next of the plurality of edge detector cells as the previous cell signal for the next of the plurality of edge detector cells, and the present cell signal from a last edge detector cell is provided to a first edge detector cell as the previous cell signal for the first edge detector cell.

Circular edge detector

Circular edge detector for measuring timing of data signals

A wordline-to-bitline timing ring oscillator circuit for evaluating storage cell access time provides data on internal bitline access timing, and in particular the total wordline select-to-bitline read output timing. Columns of a storage array are connected in a ring, forming a ring oscillator. The bitline read circuit output of each column is connected to a wordline select input of a next column, with a net inversion around the ring, so that a ring oscillator is formed. The period of oscillation of the ring oscillator is determined by the total wordline select-to-bitline read circuit output timing for a first phase and the pre-charge interval time for the other phase, with the bitline read timing dominating. The circuit may be applied both to small-signal storage arrays, with the sense amplifier timing included within the ring oscillator period, or to large-signal storage arrays, with the read evaluate circuit timing included.

Wordline-to-bitline output timing ring oscillator circuit for evaluating storage array performance

Disclosed herein is a digital system that includes a distribution network to carry a reference clock and a plurality of circuit domains coupled to the distribution network to receive the reference clock for synchronous operation in accordance with the reference clock. Each circuit domain of the plurality of circuit domains includes a respective clock generator driven by the reference clock to generate a resonant clock signal, respective circuitry coupled to the clock generator to operate in accordance with the resonant clock signal, with the circuitry including a capacitive load for the resonant clock signal and a respective inductance coupled to the circuitry and the clock generator to resonate the capacitive load of the circuitry.

Clock distribution network architecture for resonant-clocked systems

Disclosed herein is a digital system that includes a distribution network to carry a reference clock, and a circuit domain coupled to the distribution network to receive the reference clock for synchronous operation in accordance with the reference clock. The circuit domain includes a clock generator driven by the reference clock to generate a resonant clock signal, an input port to receive a control signal, and a gate coupled to the input port to discontinue application of the resonant clock signal within the circuit domain based on the control signal.

Clock distribution network architecture with resonant clock gating

A storage array including a local clock buffer with programmable timing provides a mechanism for evaluating circuit timing internal to the storage array. The local clock buffer can independently adjust the pulse width of a local clock that controls the wordline and local bitline precharge pulses and the pulse width of a delayed clock that controls the global bitline precharge, evaluate and read data latching. The delay between the local clock and the delayed clock can also be adjusted. By varying the pulse widths of the local and delayed clock signal, along with the inter-clock delay, the timing margins of each cell in the array can be evaluated by reading and writing the cell with varying pulse width and clock delay. The resulting evaluation can be used to evaluate timing margin variation within a die, as well variation from die-to-die and under varying environments, e.g., voltage and temperature variation.

Storage array including a local clock buffer with programmable timing

A method for evaluating memory cell performance provides for circuit delay and performance measurements in an actual memory circuit environment. A row in a memory array is enabled along with a set of drive devices that couple each bitline pair to the next in complement fashion to form a cascade of memory cells. The drive devices can be inverters and the inverters can be sized to simulate the bitline read pre-charge device and the write state-forcing device so that the cascade operates under the same loading/drive conditions as the operational with memory cell read/write circuits. The last and first bitline in the row can be cascaded, providing a ring oscillator or the delay of the cascade can be measured in response to a transition introduced at the head of the cascade. Weak read and/or weak write conditions can be measured by selective loading.

Method for evaluating memory cell performance

A cascaded test circuit with inter-bitline drive devices for evaluating memory cell performance provides for circuit delay and performance measurements in an actual memory circuit environment. A row in a memory array is enabled along with a set of drive devices that couple each bitline pair to the next in complement fashion to form a cascade of memory cells. The drive devices can be inverters and the inverters can be sized to simulate the bitline read pre-charge device and the write state-forcing device so that the cascade operates under the same loading/drive conditions as the operational with memory cell read/write circuits. The last and first bitline in the row can be cascaded, providing a ring oscillator or the delay of the cascade can be measured in response to a transition introduced at the head of the cascade. Weak read and/or weak write conditions can be measured by selective loading.

Cascaded test circuit with inter-bitline drive devices for evaluating memory cell performance

A method and apparatus are provided for implementing subthreshold leakage current reduction in limited switch dynamic logic (LSDL). A limited switch dynamic logic circuit includes a cross-coupled NAND and inverter logic. A dynamic node provides a first input to the NAND. A sleep signal provides a second input to the NAND. An output of the NAND provides an input to the inverter logic that inverts the NAND output and provides a complementary output. The NAND logic includes a series connected first sleep transistor receiving the sleep input. The first sleep transistor is turned OFF during the sleep mode. A second sleep transistor is connected between a voltage supply rail and the NAND output. The second sleep transistor is turned ON during the sleep mode to force high the NAND output and force low complementary output.

Growing community of inventors

Rochester, MN, United States of America

Jerry C Kao