Clock gating

About: Clock gating is a research topic. Over the lifetime, 7838 publications have been published within this topic receiving 107903 citations.

Stable high speed clock generator

Abstract: A clock generator which is provided with a circuit generating non-overlap clock from input clock, a frequency dividing circuit driven by the non-overlap clock and a latch disposed between the frequency dividing circuit and a clock driver, and whose critical pass being a cause of delay is shortened by sampling the frequency-divided output into the latch by the input clock and thereafter driving it by the clock driver, and a clock generator in which an internal clock at high speed in the internal clock logical value generating circuit is added with internal clock edge generating circuit required to operate at high speed and an output of initial stage of a buffer for inputting external clock is divided to supply to the internal clock edge generating circuit and to the other circuits, thereby capacity of the buffer required to operate at high speed in the circuit is decreased to reduce the delay of external clock.

Qualified universal clock buffer circuit for generating high gain, low skew local clock signals

Abstract: A universal qualified clock buffer circuit for generating high-performance, low-skew local clock signals from a single-phase source clock is presented. The universal qualified clock buffer circuit independently generates a separate clock signal from the single-phase clock signal and provides for conditional signal qualification for those logic circuits which require both control signals and clock signals to regulate the flow of data. An important aspect of the universal qualified clock buffer circuit is that delays on the output signal can be independently controlled. In a CMOS implementation, the delays of both rising and falling edges of the output signal are independently controlled using different FET sizes. To control skew and edge-rate uniformity, the universal qualified clock buffer circuit is capacitively matched to the impedance load of the circuit it drives.

Digital jitter attenuator using selection of multi-phase clocks and auto-centering elastic buffer

Abstract: A jitter attenuator receives data and a receive clock extracted from an input data stream. A transmit clock is generated for retransmitting the data. The transmit clock has less jitter than the receive clock but has the same average frequency. An elastic buffer or FIFO is necessary to buffer the data. The receive clock is divided into a series of write clocks for writing data into the elastic buffer, and the transmit clock is also divided into a series of read clocks for reading data from the elastic buffer. A series of multi-phase clocks is used to generate the transmit clock. The multi-phase clocks all have the same frequency but are offset in phase from one another. A phase selector, under control of a counter, selects one of the multi-phase clocks to be the transmit clock. The counter is incremented or decremented by a phase comparator. The phase comparator compares the phase of one of the write clocks to the phase of one of the read clocks. The counter is incremented when the phase of the write clock lags the read clock, selecting a multi-phase clock with a more retarded phase, but the counter is decremented when the write clock leads the read clock, selecting a multi-phase clock with a more advanced phase. Thus the phase of the transmit clock is adjusted by the phase comparison of the write and read clocks for the elastic buffer. The elastic buffer is forced to half-full by comparing a write and read clock that are separated by half the capacity of the buffer. The phase, rather than the frequency, is adjusted, eliminating the feedback to an external VCO, allowing the jitter attenuator to be integrated on a single silicon substrate.

Line loop back for very high speed application

Abstract: Method and circuitry for performing a line loop back test includes a receiver, a deserializer, and a low speed parallel loop back data multiplexer selects either the low speed parallel data from the deserializer when in loop back mode or low speed parallel input data when in normal mode. The deserializer produces a low speed clock output signal that is fed to a low speed loop back reference clock multiplexer and also to a low speed loop back clock multiplexer. Both the loop back reference clock multiplexer and the loop back clock multiplexer select the low speed clock output signal from the deserializer when in line loop back mode. A clock multiplying unit converts the output of the low speed loop back reference clock multiplexer into a high speed clock signal. The serializer generates the high speed serial transmitter data in synchronization with the high speed clock signal received from a clock multiplying unit. A clock divider circuit converts the high speed clock signal from the clock multiplying unit into a low speed FIFO output clock. A first-in-first-out buffer receives the low speed parallel output data in synchronization with a clock multiplexer output, and transmits low speed parallel FIFO data to the serializer in synchronization with the low speed FIFO output clock. A low speed parallel loop back data buffer provides coupling between the deserializer and the low speed parallel loop back data multiplexer, and a low speed loop back clock buffer provides coupling between the deserializer and the loop back reference clock multiplexer and the loop back clock multiplexer.

Clock generating circuit for use in semiconductor memory device

Abstract: In a semiconductor memory integrated circuit device, power consumption and clock noise are reduced by providing a plurality of separately controlled internal clock signal generators. All of the internal clock signal generators receive an external clock signal, so as to provide respective internal clock signals that are synchronized with the external clock signal. However, each of the internal clock signal generators is separately controlled depending upon the present operating mode of the memory, so that individual internal clock signals are generated only when required.