Abstract: To include a first level shift circuit that converts a first internal clock signal having an amplitude value of a first voltage into a second internal clock signal having an amplitude value of a second voltage, a second level shift circuit that converts a first internal data signal having the amplitude value of the first voltage into a second internal data signal having the amplitude value of the second voltage, a clock dividing circuit that generates third and fourth internal clock signals, which are complementary signals, based on the second internal clock signal, and an output circuit that outputs external data signals continuously from a data output terminal in synchronization with the third and fourth internal clock signals based on the second internal data signal. According to the present invention, because a level shift of a signal is performed before it is input to the output circuit, there occurs no skew in output data.

Abstract: A feedback loop circuit includes a phase detector and delay circuits. The phase detector generates an output signal based on a delayed periodic signal. The delay circuits are coupled in a delay chain that delays the delayed periodic signal. Each of the delay circuits includes variable delay blocks and fixed delay blocks that are coupled to form at least two delay paths for an input signal through the delay circuit to generate a delayed output signal. Delays of the variable delay blocks in the delay circuits vary based on the output signal of the phase detector. Each of the delay circuits reroutes the input signal through a different one of the delay paths to generate the delayed output signal based on the output signal of the phase detector during operation of the feedback loop circuit.

Abstract: A power control circuit includes a check unit that receives a reference clock and generates a check signal for cyclically activating a feedback loop of a DLL circuit, a phase detecting unit that detects a phase difference between the reference clock and a feedback clock, and generates a phase difference detection signal, and a signal combining unit that generates a power cutoff signal in response to a locking completion signal, the check signal, and the phase difference detection signal.

Abstract: A phase detector circuit generates a phase comparison signal based on a phase difference between first and second periodic signals during a test mode. Phases of the first and the second periodic signals do not change in response to variations in a signal generated by the phase detector circuit during the test mode. A lock generation circuit generates an output signal based on the phase comparison signal that indicates if the first and the second periodic signals are within a lock window of the lock generation circuit. The lock window of the lock generation circuit changes in response to a variation in a control signal.

Abstract: A DLL circuit includes a delay line that adds, when receiving a reference signal, a delay amount to the phase of the reference signal by using each delay element and outputs a delay signal for each delay element. The DLL circuit includes a phase detector that compares the phase of a delay signal delayed by all the delay elements and the phase of the reference signal to obtain a phase difference by using the delay signal adjusted by a phase adjustment circuit and the reference signal. The DLL circuit includes a delay element control circuit that inputs a value, by which the delay signal to be compared by the phase detector is synchronized with the reference signal to be compared by the phase detector and which is a control voltage value generated from the phase difference output from the phase detector, into the delay elements of the delay line.

Abstract: A delay locked loop includes a replica delay oscillator unit, a division unit, a pulse generation unit, a code value output unit, and a delay line. The replica delay oscillator unit generates a replica oscillation signal having a period corresponding to a replica delay. The division unit receives the replica oscillation signal and a clock signal and divides the replica oscillation signal and the clock signal at a first or second ratio in response to a delay locking detection signal. The pulse generation unit generates a delay pulse having a pulse width corresponding to a delay amount for causing a delay locking. The code value output unit adjusts a code value corresponding to the pulse width of the delay pulse in response to the delay locking detection signal. The delay line delays the clock signal in response to the code value.

Abstract: Apparatus, systems, and methods are disclosed that operate to delay a periodic input signal in one or more delay elements of a group of delay elements to generate a periodic output signal and to vary a power supply to the delay elements. Additional apparatus, systems, and methods are disclosed.

Abstract: Semiconductor devices are disclosed providing synchronization circuits for synchronized signal distribution for a plurality of devices in a semiconductor device. The synchronization apparatus includes an independent synchronization circuit and a dependent synchronization circuit. The independent synchronization circuit may be configured to receive a source signal and to generate a first destination signal substantially synchronized with the source signal. The dependent synchronization circuit may be coupled to the independent synchronization circuit and configured to receive the source signal and to generate a second destination signal substantially synchronized with the source signal.

Abstract: In a method for controlling the loop delay in a sigma-delta modulator having a loop including an integrator, an analog-to-digital converter, a digital-to-analog converter, and an adder-subtractor, at least one phase-control programmable digital command representing a phase shift is applied to one of the clock signals of the converters of the loop to adjust the relative phase between a clock signal of the analog-to-digital converter and a clock signal of the digital-to-analog converter. A sigma-delta modulator for converting an analog signal implements the method.

Abstract: A feedback loop circuit includes a phase detector and delay circuits. The phase detector generates an output signal based on a delayed periodic signal. The delay circuits are coupled in a delay chain that delays the delayed periodic signal. Each of the delay circuits comprises variable delay blocks and fixed delay blocks that are coupled to form at least two delay paths for an input signal through the delay circuit to generate a delayed output signal. Delays of the variable delay blocks in the delay circuits vary based on the output signal of the phase detector. Each of the delay circuits reroutes the input signal through a different one of the delay paths to generate the delayed output signal based on the output signal of the phase detector during operation of the feedback loop circuit. Each of the variable delay blocks and the fixed delay blocks is inverting.

Abstract: In some embodiments, a feedback loop circuit includes a phase detector, first and second charge pumps that are each coupled to receive an output signal of the phase detector, a first low pass filter, a second low pass filter coupled to an output of the second charge pump, a clock signal generation circuit having first and second control inputs, a first switch circuit coupled between the first low pass filter and the second low pass filter, and a second switch circuit coupled to the first low pass filter and the first control input of the clock signal generation circuit.

Abstract: A sampling section (100A) includes a sampling filter (102) that converts a continuous-time signal into a discrete-time signal and applies filtering of low-pass characteristics and a one-bit quantizer (107) that outputs a quantized signal representing a time-dependent change in the discrete-time signal. A synchronization section (100B) includes a phase difference detector (110) that calculates the phase difference between an inspection signal and the quantized signal and a delay control circuit (114) that feeds back the inspection signal to the phase difference detector at the timing set in consideration of a delay amount corresponding to the phase difference. When the phase difference between the inspection signal and the current quantized signal shows the same phase, the phase of the inspection signal is detected as a reference phase.

Abstract: A reference circuit and method for mitigating switching jitter and delay-locked loop (DLL) using same are provided. The reference circuit and method determine a number of steps of a fine delay line (FDL) that are equivalent to a step of a coarse delay line (CDL). Switching jitter of the DLL is reduced since the delay of the step of the CDL that is switched when on an underflow or overflow condition of the FDL is detected is equivalent to the delay of the provided number of steps of the FDL.

Abstract: An improved bias generator incorporates a reference voltage and/or a reference current into the generation of bias voltages. In some cases, the output of a biased delay element has a constant voltage swing. A delay line of such constant output voltage swing delay elements may be shown to provide reduced power consumption compared to some known self-biased delay lines. Furthermore, in other cases, providing the reference current to a novel bias generator allows a delay line of delay elements biased by such a novel bias generator to show reduced sensitivity to operating conditions, reduced sensitivity to variation in process parameters and improved signal quality, thereby providing more robust operation.

Abstract: A delay locked loop circuit includes a delay locked loop receiving an external clock, a frequency detector delaying an input frequency signal to generate a plurality of strobe signals and outputting a check signal indicating that the frequency of the input frequency signal is equal to or lower than a reference frequency when all of the strobe signals are positioned within a first-status section of one cycle of the input frequency signal, a delay lock reset unit generating a reset signal to reset the frequency detector and an activation signal to enable the delay locked loop to perform a delay lock process, and a direct phase detector controlling a coarse locking window on the basis of the check signal and generating a pair of phase detection signals indicating logic levels of the external clock. According to this configuration, since the coarse locking window is controlled as per a frequency band, it is possible to prevent a failure of a coarse locking and to achieve an improved circuit performance.

Abstract: A delay locked loop (DLL) apparatus includes a first delay unit converting a reference clock into a rising clock. A second delay unit converts the reference clock into a falling clock, and a replica delay unit replica-delays the rising clock. A first phase detector compares the phases of the reference clock and the delayed rising clock to output a first detection signal corresponding to the compared phases. A controller synchronizes the rising edge of the rising clock with the rising edge of the reference clock according to the first detection signal of the first phase detector. A second phase detector compares the phases of the synchronized rising clock and the synchronization clock to output a second detection signal corresponding to the compared phases. The DLL apparatus compensates for a skew between an external clock and data and between external and internal clocks by employing a single replica delay unit.

Abstract: A delay locked loop circuit comprising a VCDL which outputs a feedback clock by delaying an input clock in accordance with a magnitude of a control voltage, a phase comparator which detects a phase difference between the feedback clock and a reference clock by comparing the feedback clock with the reference clock, and outputs an Up-signal for raising the control voltage and a Down-signal for lowering the control voltage in accordance with the phase difference, a control voltage generation circuit which determines the control voltage in accordance with the Up-signal and the Down-signal, and outputs the control voltage to the VCDL, and a reset circuit which resets the phase comparator based on a logical OR between the reference clock and a first intermediate clock which is a signal obtained by delaying the input clock by the VCDL and is output before the feedback clock.

Abstract: A delay locked loop (DLL) circuit has a first delay line that delays a received external clock signal for a fine delay time and then outputs a first internal clock signal; a duty cycle correction unit that corrects a duty cycle of the first internal clock signal and then outputs a second clock signal; a second delay line that delays the second clock signal for a coarse delay time and then outputs a second internal clock signal; and a phase detection and control unit that detects the difference between the phases of the external clock signal and the fed back second internal clock signal, and controls the fine delay time and the coarse delay time. The DLL circuit performs coarse locking and fine locking by using different type delay cells, and thus consumes a small amount of power and robustly withstands jitter and variation in PVT variables.

Abstract: A circuit, delay-locked loop, memory device, system and method of synchronizing a clock are described. A circuit generally includes a delay line configured to delay an external clock signal to produce a substantially in-phase output clock signal, a main loop configured to control delay through the delay line, and a secondary loop configured to adjust delay through the main loop. The clock synchronization method generally includes adjusting a delay along a delay line in response to a first phase difference between an input clock to the delay line and a shared clock signal delayed by a shared dynamic I/O model of an output driver. The method further includes adjusting the shared dynamic I/O model in response to a second phase difference between an output clock signal and the shared clock signal.

Abstract: A frequency divider section generates a frequency-divided clock RSELO by dividing the frequency of an internal clock LCLK, which lags behind an external clock in phase, and generates a delayed frequency-divided clock RSELI by delaying the frequency-divided clock RSELO. A signal input from the outside in synchronization with an internal clock PCLK which lags behind the external clock in phase is held in a latch circuit in synchronization with the delayed frequency-divided clock RSELI. Then, an output signal of the latch circuit is read into a latch circuit in synchronization with the frequency-divided clock RSELO and is output as a signal which is synchronized with the internal clock LCLK. In addition, a frequency divider section includes a variable divider which divides the frequency of the internal clock LCLK by a predetermined divide ratio which can be changed.

Abstract: An up/down detection unit samples a received data signal and determines in which of first through third areas of the data signal the logic level of the data signal transitions, wherein the data sampling clock signal, the first edge sampling clock signal, and the second edge sampling clock signal are sequentially activated. A lower limit detection unit detects a lower limit of the first area if the logic level of the data signal transitions in the first area. An upper limit detection unit detects an upper limit of the third area if the logic level of the data signal transitions in the third area. A phase detection unit determines a delay amount indicating the amount by which the data signal is to be delayed according to the upper limit and lower limit detected. A buffer unit delays the data signal by the delay amount determined by the phase detection unit.

Abstract: A delay locked loop (DLL) circuit includes a clock input buffer that generates a reference clock signal by buffering an external clock signal and outputs the reference clock signal by correcting a duty cycle of the reference clock signal in response to a duty cycle control signal. The DLL circuit also includes a timing compensation unit configured that generates a compensation reference clock signal by compensating for a toggle timing of the reference clock signal that is changed during the duty cycle correction operation in response to a timing control signal. The DLL circuit further includes and a duty cycle control unit that generates the duty cycle control signal and the timing control signal by detecting the duty cycle of the reference clock signal.

Abstract: A method for tracking a delay locked loop (DLL) clock is described. An external clock signal is allowed to pass through delay cells of a DLL during a first period of the external clock signal when a transition edge of a track signal applied on the DLL occurs. Then, when a transition edge of a sensing signal applied on the DLL occurs at a start of a second period of the external clock signal, the external clock signal is inhibited to pass through the delay cells and the number of the delay cells through which the external signal pass during the first period of the external clock signal is counted. When a reset signal is asserted, a delay time of each delay cell is reset such that a ratio of the delay time to the period of the external clock signal is kept from 10% to 15%.

Abstract: A delay locked loop circuit includes a delay replica model unit for reflecting a delay time of an actual output path to a source clock and outputting the reflected source clock as a delay replica clock, a detector for detecting a remaining time after subtracting a time corresponding to a multiple of a clock cycle of the source clock from a time corresponding to a phase difference between the delay replica clock and the source clock, and a delay locking unit for delaying the source clock for a delay time to synchronize a clock generated by delaying the source clock for the detected remaining time of the detector with a phase of the source clock.

Abstract: In a reception apparatus 1, a multiphase sampling clock signal is generated by a sampling clock signal generation circuit 40, based on a clock signal which has been phase-adjusted by a phase adjustment circuit 50. The data of each of the bits of a serial data signal is sampled and output by a sampler block circuit 30n, with timing indicated by the sampling clock signal. The amount of phase adjustment of the clock signal in the phase adjustment circuit 50 is set such that the delay time from generation of the multiphase sampling clock signal in the sampling clock signal generation circuit 40 until indication of the sampling timing by the sampling clock signal in the sampler block circuit 30n is canceled.

Abstract: An interconnection system is described where data lanes may be exchanged between lines at intervals along a transmission path so that the differential time delay between bits on a plurality of the lines is reduced when determined at a receiving location. The data lanes may be bound to the lines through the operation of a configurable switch, or by a configurable switch in conjunction with predetermined manufactured connections, or a combination of the techniques. The wiring of a connectorized node module, which may include a memory device, may be configured so that the differential time delay between pairs of input lines of a node, as measured at the output of a node, is reduced.

Abstract: In response to an input signal, in a first delay line, a delay amount is added to a phase of the input signal by each delay unit. In a DLL circuit, in response to an external signal that can be externally switched to a signal different in frequency is accepted, in a second delay line, a delay amount is added to the phase of the external signal by each delay unit. The phase of a delay signal delayed by all delay units of the second delay line and the phase of the external signal to which no delay amount added are compared to output a phase difference. A control voltage value that is a value for synchronizing the delay signal to be compared by the phase comparator and is generated from the phase difference output from the phase comparator is input to each of the delay units.

Abstract: A fast locking delay-locked loop (DLL), which can also operate as a clock data recovery circuit (CDR), includes a delay chain, a sampling circuit and a transition detector. An input signal and delayed versions of the input signal generated by the delay chain are sampled by the sampling circuit. The outputs of the sampling circuit are provided to a transition detector which selects one of the input signal and its delayed versions determined to have signal transitions most closely aligned with a sampling edge of a clock. The selected signal and the clock are provided as inputs to a phase discriminator which generates an error signal representing a level of phase mismatch between the inputs. The error signal is fed back to the sampling circuit to maintain phase lock between the clock signal and the input bit stream.

Abstract: A semiconductor integrated circuit is provided. The semiconductor integrated circuit includes: a delay locked loop (DLL) output block configured to delay an input clock signal by a predetermined time in response to a plurality of delay control signals and provide a DLL clock signal; a locking control block configured to compare a phase of a reference clock signal and a phase of a feedback clock signal, and synchronize the phase of the reference clock signal and the phase of the feedback clock signal in response to the plurality of delay control signals; and a locking detection block configured to detect whether the phase of the reference clock signal and the phase of the feedback clock signal are synchronized and the DLL clock signal is locked, wherein, when the DLL clock signal is locked, the locking control block provides the reference clock signal, which is obtained by dividing the input clock signal by n (where n is a natural number equal to or greater than 2), as an internal DLL clock signal.

Abstract: A phase synchronization apparatus includes a bias control unit configured to sequentially delay an input clock signal to generate bias control signals having multiple bits, a bias generation unit configured to generate a pull-up bias voltage having a level that corresponds to logical values of the bias control signals, and to generate a pull-down bias voltage in response to a control signal; and a voltage controlled oscillator configured to include a plurality of delay cells respectively having a pull-up terminal and a pull-down terminal to generate an output clock signal in response to the control voltage, wherein the pull-up bias voltage is supplied to the pull-up terminals of the respective delay cells and the pull-down bias voltage is supplied to the pull-down terminals of the respective delay cells.

Abstract: A semiconductor memory device includes a delay locked loop for achieving a delay locked state by correcting a phase difference between a reference clock and an internal delayed clock and for indicating the state that a larger delay amount than a maximum delay amount of a delay line is required, or a smaller delay amount than a minimum delay amount of delay line is required. A control unit resets the delay locked loop according to the state of the delay line.

Abstract: A phase shift circuit that includes two, rather than four, delay chains and corresponding selectors is described. This provides a significant area savings and reduces the intrinsic delay of the phase shift circuit, which is particularly beneficial for embodiments in which there is no intrinsic delay matching. In one implementation, the phase shift circuit includes a first delay circuit and a matching delay circuit. The first delay circuit provides a first delay that includes a first intrinsic delay and a first intentional delay. The delay matching circuit provides a matching delay that matches the first intrinsic delay. In one implementation, the phase shift circuit also includes a second delay circuit to provide a second delay that includes a second intrinsic delay and second intentional delay, where the second intrinsic delay matches the first intrinsic delay and the second intentional delay is half as long as the first intentional delay.

Abstract: A Delay-Locked Loop (DLL) uses a delay line to delay a first signal by a “delay time”, thereby generating a second signal. A capacitor is charged at a first rate starting at a first edge of first signal and continuing until an edge of the second signal. The capacitor is then discharged at a second rate until another edge of the first signal. A control loop controls the delay time such that the amount the capacitor is charged is the same as the amount the capacitor is discharged. The delay time is constant and is substantially independent of variations in the duty cycle of the first signal. In one example, duty cycle distortion cancellation is accomplished by changing the first rate proportionally with respect to changes in first signal duty cycle. In another example, the first and second rates are independent of the duty cycle of the first signal.

Abstract: Closed-loop duty-cycle correctors (DCCs), clock generators, memory devices, systems, and methods for generating an output clock signal having a particular duty cycle are provided, such as clock generators configured to generate an output clock signal synchronized with a received input clock signal having a predetermined duty cycle. Embodiments of clock generators include closed-loop duty cycle correctors that receive an already-controlled and corrected output signal. For example, DLL control circuitry and DCC control circuitry may each adjust a delay of a variable delay line. The DLL control circuitry adjusts the delay such that an output clock signal is synchronized with an input clock signal. The DCC control circuitry detects a duty cycle error in the output clock signal and adjusts the delay of the variable delay line to achieve a duty cycle corrected output signal.

Abstract: Clock circuits, memories and methods for generating a clock signal are described. One such clock circuit includes a delay locked loop (DLL) configured to receive a reference clock signal and generate an output clock signal having an adjustable phase relationship relative to the reference clock signal, and further includes a clock jitter feedback circuit coupled to a clock tree and the DLL. The clock jitter feedback circuit is configured to synchronize a clock jitter feedback signal and a DLL feedback signal that is based on the output clock signal. The clock jitter feedback circuit is further configured to provide the clock jitter feedback signal to the DLL for synchronization with a buffered reference clock signal. The clock jitter feedback signal is based on and generated in response to receiving a distributed output clock signal from the clock tree circuit and the buffered reference signal is based on the reference clock signal.

Abstract: A delay module, a delay method, a clock detection apparatus, and a digital locked loop (DLL) are disclosed. The delay module includes a first delay unit, a second delay unit and an inverter. Each of the first delay unit and the second delay unit include two logic gates adapted to invert a phase: a logic gate for gating and a logic gate for delaying. These two logic gates are electrically connected. The input port of the logic gate for gating of the first delay unit is electrically connected to the output port of the inverter; the output port of the logic gate for delaying of the first delay unit is electrically connected to the input port of the logic gate for delaying of the second delay unit; the input port of the inverter is electrically connected to the input port of the logic gate for gating of the second delay unit; the input port of the inverter is adapted to input a clock signal to be delayed, and the logic gate for delaying of the second delay unit is adapted to output a delayed clock signal.

Abstract: A locking state detector includes a phase comparing unit configured to compare a reference clock signal and a feedback clock signal to generate a first phase difference distinction signal to distinguish a first phase difference range, and a second phase difference distinction signal to distinguish a second phase difference range wider than the first phase difference range, and a locking state setting unit configured to generate a locking state signal in response to the first phase difference distinction signal and the second phase difference distinction signal.

Abstract: A clock data restoration device 1, which restores a clock signal and data on the basis of an inputted digital signal, comprises an equalizer 10, a sampler 20, a clock generator 30, an equalizer controller 40, and a phase monitor 50. A clock signal CK or CKX as a clock signal restored on the basis of the input digital signal is generated through loop processing by the sampler 20 and the clock generator 30. The level adjustment amount of a high frequency component of the digital signal by the equalizer 10 is controlled through loop processing by the equalizer 10, the sampler 20 and the equalizer controller 40.

Abstract: A semiconductor integrated circuit includes a DLL controlling block configured to enable or disable an update enable signal by detecting a change in a voltage level of a phase detecting signal during a predetermined time when an operation enable signal and a threshold phase difference detecting signal are enabled, and a delay locked loop (DLL) circuit configured to generate an output clock signal by delaying and driving the reference clock signal and to control a frequency of a change in the delay amount of the reference clock signal in response to the update enable signal.

Abstract: Jitter is stably reduced. An input clock signal (CLKi) is outputted as an output clock signal (CLKo) via a voltage controlled delay circuit (12), and in addition a delay amount in the voltage controlled delay circuit (12) is controlled based on a result of a phase comparison of the input clock signal (CLKi) and the output clock signal (CLKo). A phase comparison result judging circuit (15) adds up results of phase comparison of the input clock signal (CLKi) and the output clock signal (CLKo) over a prescribed time, and controls the delay amount based on a distribution of addition results.

Abstract: The present invention relates to a delay-locked loop-based multiphase clock generator that generates a plurality of multiphase clocks from an input clock signal using a voltage controlled delay line including a plurality of dummy cells. The delay-locked loop-based multiphase clock generator includes an anti-harmonic lock circuit that receives an input clock and a reference clock of multiple clocks, determines whether a pulse signal derived from the input clock is within a normal locking range of the reference clock, and outputs a compulsory control signal to compulsorily control an output signal of a phase detector if it is determined that the pulse signal is not within the normal locking range.

Abstract: A wideband delay-locked loop (DLL) circuit includes an internal clock signal generating unit providing an internal control signal by selecting and interpolating between two clock delay signals during a primary phase locking operation. The internal clock signal may be modified by a secondary phase locking operation if more delay is required to phase lock the internal clock signal to an external clock signal. A phase detection/control circuit generates various control signals based on a phase comparison of the internal clock signal and the external clock signal.

Abstract: In response to an input signal, in a first delay line, a delay amount is added to a phase of the input signal by each delay unit. In a DLL circuit, in response to an external signal that can be externally switched to a signal different in frequency is accepted, in a second delay line, a delay amount is added to the phase of the external signal by each delay unit. The phase of a delay signal delayed by all delay units of the second delay line and the phase of the external signal to which no delay amount added are compared to output a phase difference. A control voltage value that is a value for synchronizing the delay signal to be compared by the phase comparator and is generated from the phase difference output from the phase comparator is input to each of the delay units.

Abstract: A delay locked loop circuit includes a phase comparison unit configured to compare a reference clock with a feedback clock and to output a phase comparison signal, a clock delay unit configured to delay a first reference clock in response to the phase comparison signal, to output a first delay locked clock, to delay one of the first delay locked clock and a second reference clock according to a frequency information signal, and to output a second delay locked clock, a delay locked clock generating unit configured to output a delay locked clock as a phase-mixed clock of the first delay locked clock and the second delay locked clock, the first delay locked clock, or the second delay locked clock in response to the frequency information signal and a delay transfer signal, and a delay replica model unit configured to reflect a delay condition of the reference clock.

Abstract: A delay locked loop controls a plurality of delay blocks included in a delay line and thus generate a plurality of clock signals which have a frequency obtained by multiplying a frequency of a reference clock signal, an accurate phase delay, and a constant duty cycle. The delay locked loop calculates an initial delay value and applies it to the delay blocks, thereby preventing harmonic locking and reducing locking time.

Abstract: The DLL circuit includes a control circuit which controls bias currents of the unit delay circuits according to an externally input column address strobe writing latency (CWL) signal, and/or a DCC control circuit which adjusts steps of a DCC current of the DCC according to the externally input column address strobe writing latency (CWL) signal. The CWL signal may be input by a semiconductor memory device and may be indicative of a column address strobe writing latency of the semiconductor memory device. The semiconductor memory device may be a double data rate (DDR) synchronous DRAM (SDRAM) device.

Abstract: A delay locked loop circuit includes a delay locking unit configured to output a first internal clock and a second internal clock, a rising edge of which is synchronized with that of the first internal clock by delaying a compensated external clock for compensating a skew of a semiconductor memory device; a duty ratio compensation unit configured to generate the compensated external clock by compensating a duty ratio of an external clock of the semiconductor memory device and to compensate duty ratios of the first and second internal clocks; and a clock control unit configured to control an activation state of the second internal clock after the duty ratio compensation of the external clock.

Abstract: A DLL circuit includes a first phase comparing circuit that compares phases between an input clock signal and an output clock signal, a first delay circuit that delays the output clock signal, and a second phase comparing circuit that compares phases between the input clock signal and an output signal of the first delay circuit. A delay amount in the variable delay circuit is controlled based on a comparison result of the first phase comparing circuit and a comparison result of the second phase comparing circuit.

Abstract: A Delay Locked Loop (DLL) includes a replica delay unit configured to delay an output clock to generate a feedback clock; a phase detector configured to measure a phase difference between the feedback clock and an input clock; a quantization unit configured to quantize the phase difference measured by the phase detector; and a delay unit configured to delay the input clock based on a quantization result from the quantization unit to generate the output clock.

Abstract: An apparatus for testing setup/hold time includes a plurality of data input units, each configured to calibrate setup/hold time of input data in response to selection signals and setup/hold calibration signals, and an off-chip driver calibration unit configured to generate the selection signals and the setup/hold calibration signals by using the input data input of one of the plurality of data input units.