476 results about "Clock buffer" patented technology

A receiver for receiving a stream of symbols clocked at a first rate, and providing the symbols at a second clock rate uses two buffers. Incoming symbols are written to a first dual clock buffer at the first rate, and read from the first and second buffer, at the second rate. Underflow of the first buffer is signaled to the second buffer, thereby avoiding the need to insert defined clock compensation symbols at the second rate. Symbols received at the second buffer while underflow is signaled may be ignored. Conveniently, the second buffer may also be used to align symbol data across multiple symbol streams using periodic alignment symbols. An exemplary embodiment conforms to the PCI Express standard.

A clock modulator spreads the frequency spectrum of an input clock to generate an output clock. A capacitor is connected to an intermediate clock node by a load-switching transistor. When the transistor is turned on, the capacitor increases the loading on the intermediate clock node, increasing delay. When the transistor is turned off, the delay is reduced. Output clock cycle periods are extended when delay is added, and reduced when the transistor turns off. A counter or sequencer is clocked by the input clock and drives the load-switching transistor. The transistor is turned on and off for alternate cycles when the counter is a toggle flip-flop, spreading the frequency over two frequencies every two clock cycles. Two capacitors of different sizes, connected to the intermediate clock node by two transistors, can be switched by a 2-bit sequencer, spreading the output clock over 7 frequencies every 7 clock cycles.

A system includes modules, a clock generator that generates a first clock signal that is applied to the modules, and a chipset that controls the modules, the chipset having a clock buffer that generates a second clock signal. The system includes a first clock line that transfer the first clock signal to the clock buffer, the first clock line connected between the clock generator and a first termination circuit. The system includes a second clock line that transfer the second clock signal to the modules, the second clock line electrically isolated from the first clock line, the second clock line connected between the clock buffer and a second termination circuit.

An integrated circuit chip comprises a plurality of clock distribution sub-networks each including a clock input for receiving a clock signal, each of the clock distribution sub-networks having a capacitance, as seen from the clock input, substantially equivalent to others of the clock distribution sub-networks; and a structured clock buffer having a size based on a load of the clock distribution sub-networks, and providing the clock signal to the clock distribution sub-networks.

According to one example embodiment, a buffer, e.g., in a clock/signal distribution apparatus is provided that substantially reduces jitter due to power supply noise. Decoupler and input stage isolates load from the top rail power supply (V_DD). In a more particular embodiment, jitter contributions from the bottom rail power supply (V_SS) can be minimized by cross-coupled load devices within load. Substantial independence from process and temperature is facilitated through the use of current bias, such as Proportional to Absolute Temperature (PTAT) current bias.

A semiconductor memory device includes a first clock buffer for outputting a first internal clock signal in response to an inverted signal of the system clock signal and for correcting a duty cycle ratio of the first internal clock signal in response to a control signal; a second clock buffer for outputting a second internal clock signal in response to the system clock signal and for correcting a duty cycle ratio of the second internal clock signal in response to the control signal; an analog duty cycle correction circuit for outputting the control signal corresponding to the duty cycle ratio of the first and second internal clock signals; a mixing circuit for mixing the first and second internal clock signals and for outputting a third internal clock signal whose duty cycle is corrected; and a DLL circuit for outputting a delay-locked clock signal by using the third internal clock signal.

A clock control circuit includes a multiphase clock generating circuit receiving an output signal of a input buffer for generating multiphase clocks; a selector circuit receiving multiphase clocks output from the multiphase clock generating circuit for selecting one of the multiphase clocks; a first variable delay circuit for delaying the output of the selector circuit; a clock buffer dummy receiving the output signal of the variable delay circuit ; a phase comparator circuit for detecting a phase difference between an output from the multiphase clock generating circuit and an output of the clock buffer dummy; and a filter for smoothing the output of the phase comparator circuit. The first variable delay circuit has its delay time varied by the output of the filter. The clock control circuit further includes a second variable delay circuit, receiving the output signal of the input buffer, having its delay time varied by the output of the filter; an adder circuit for adding the filter output and an input set value; a third variable delay circuit, receiving the output signal of the input buffer, having its delay time varied by the output of the adder circuit; and clock buffers receiving output signals of respective ones of the second and third variable delay circuits.

A novel iterative latch placement scheme wherein the latches are gradually pulled by increasing attraction force until they are eventually placed next to a clock distribution structure such as a local clock buffer (LCB). During the iterations, timing optimizations such as gate sizing and re-buffering are invoked in order to keep the timing estimation accurate. By applying the iterative clock net weighting adjustment, the present invention allows tighter interaction between logic placement and clock placement which leads to higher quality timing and significant power savings.

There is provided a DLL capable of controlling a duty rate of a clock by a fuse option or an EMRS input. The DLL includes a first clock buffer, a second clock buffer, a first delay line, a second delay line, a shift register, a first duty control unit, a second duty control unit, a first DLL driver, a second DLL driver, a delay model, a phase comparator, and a shift control unit. In the DLL, a first duty control unit and a second duty control unit control each duty rate of the output clocks of a first and a second delay lines respectively through the EMRS input or the fuse option. Therefore, it is possible to control the duty rate of DLL clocks through the EMRS input or the fuse option.

A circuit for measuring timing uncertainty in a clocked digital path and in particular, the number of logic stages completed in any clock cycle. A local clock buffer receives a global clock and provides a complementary pair of local clocks. A first local (launch) clock is an input to a delay line, e.g., 3 clock cycles worth of series connected inverters. Delay line taps (inverter outputs) are inputs to a register that is clocked by the complementary clock pair to capture progression of the launch clock through the delay line and identify any variation (e.g., from jitter, VDD noise) in that progression. Global clock skew and across chip gate length variation can be measured by cross coupling launch clocks from a pair of such clock buffers and selectively passing the local and remote launch clocks to the respective delay lines.

Methods and apparatus are provided for clock skew calibration in a clock and data recovery system. One aspect of the invention compensates for skew among a plurality of clocks in a clock and data recovery system. The clocks are applied to a plurality of latches to sample an incoming signal. A reference signal, such as a Nyquist signal, is applied to a data input of each of the latches. Statistics of “early” and “late” corrections applied to at least one of the clocks by a bang-bang phase detector in the clock and data recovery system are evaluated and a delay of a clock buffer associated with the at least one clock is adjusted to obtain approximately a 50% early-to-late ratio for the at least one clock. The clock and data recovery system ensures that the early-to-late ratio for the sum of the plurality of clocks is approximately 50%.

A method and apparatus for operating a source synchronous receiver. In one embodiment, a source synchronous receiver may include a clock receiver comprising a clock detector and a clock signal buffer. The clock detector may be configured to detect a first clock signal and assert a clock detect signal responsive to detecting the first clock signal. The clock buffer may receive the first clock signal and produce a second clock signal, which may be driven to a digital locked loop (DLL) circuit, where the second clock signal is regenerated and driven to a data buffer of the source synchronous receiver. The clock detect signal may be received by a clock verification circuit. The clock verification circuit may be configured to initiate a reset of the source synchronous receiver upon a failure to receive the clock detect signal. The resetting of the source synchronous receiver may be performed locally, and does not reset the core logic of the device in which it is implemented, nor any other source synchronous port on the device. Thus, other source synchronous ports on the device, as well as the core logic, may be able to continue operations as normal. The method and apparatus may include a source synchronous receiver that is hot-swappable.

A conditional clock buffer circuit is disclosed. In one embodiment, a conditional clock buffer circuit includes a precharge circuit, a first transistor and a second transistor coupled to the precharge circuit via the first node and the second node, a third transistor coupled to the first transistor and the second transistor. The first transistor may be activated responsive to a condition external to the clock buffer circuit. When the first transistor is activated, an output clock signal driven by the clock buffer circuit may be inhibited.

A synchronizing circuit includes an internal partial power supply interruption circuit section which can be subjected to a power supply interruption and includes a data transmission register configured to output data for controlling a power supply interruption and a clock enable control register configured to output an enable signal; an internal partial power supply interruption control circuit section configured to control a power supply interruption and includes a gated clock buffer configured to control a clock signal based on the enable signal, and a data reception register configured to take in data based on the controlled clock signal; and an isolation cell configured to output an output from the internal partial power supply interruption circuit section as a fixed value when the internal partial power supply interruption circuit section has been subjected to a power supply interruption.

The invention provides a clock adjustment circuit and an adjustment method for a clock circuit. The clock adjustment circuit comprises a clock buffer amplifier, a phase discriminator and a duty cycle adjustment circuit, wherein the clock buffer amplifier is used for receiving an external differential clock signal, shaping the differential clock signal into a single-end square wave clock signal and outputting the single-end square wave clock signal; the phase discriminator is used for receiving the single-end square wave clock signal from the clock buffer amplifier and a feedback signal from the duty cycle adjustment circuit, comparing the phase of the single-end square wave clock signal with the phase of the feedback signal to acquire a phase difference, and outputting the phase difference; and the duty cycle adjustment circuit is used for adjusting the duty cycle of the feedback signal by using the phase difference to acquire an adjusted feedback signal. The differential signal is shaped into the single-end square wave clock signal, the single-end square wave clock signal is compared with the feedback signal to acquire the phase difference, and the duty cycle is adjusted according to the phase difference, so that the complexity of duty cycle adjustment and hardware implementation can be effectively reduced, phase errors and the ripple waves of control voltage can be reduced, and adjustment accuracy is improved.

A technique generates small scale clock trees using a spine-based architecture (using spine routing) while also using clustered placement. Techniques are used to control clock sink cluster contents in order to minimize clock skew, minimize clock buffer count, and minimize use of routing resources. This approach also provides the user with ample structure and control to customize small efficient clock trees, and can also reduce clock power consumption.