US20010022745A1 - Delay locked loop for use in semiconductor memory device - Google Patents
Delay locked loop for use in semiconductor memory device Download PDFInfo
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- US20010022745A1 US20010022745A1 US09/745,490 US74549000A US2001022745A1 US 20010022745 A1 US20010022745 A1 US 20010022745A1 US 74549000 A US74549000 A US 74549000A US 2001022745 A1 US2001022745 A1 US 2001022745A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
- G11C11/34—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices
- G11C11/40—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors
- G11C11/401—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors forming cells needing refreshing or charge regeneration, i.e. dynamic cells
- G11C11/4063—Auxiliary circuits, e.g. for addressing, decoding, driving, writing, sensing or timing
- G11C11/407—Auxiliary circuits, e.g. for addressing, decoding, driving, writing, sensing or timing for memory cells of the field-effect type
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/22—Read-write [R-W] timing or clocking circuits; Read-write [R-W] control signal generators or management
- G11C7/222—Clock generating, synchronizing or distributing circuits within memory device
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/22—Read-write [R-W] timing or clocking circuits; Read-write [R-W] control signal generators or management
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
- H03K5/13—Arrangements having a single output and transforming input signals into pulses delivered at desired time intervals
- H03K5/133—Arrangements having a single output and transforming input signals into pulses delivered at desired time intervals using a chain of active delay devices
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
- H03K5/13—Arrangements having a single output and transforming input signals into pulses delivered at desired time intervals
- H03K5/135—Arrangements having a single output and transforming input signals into pulses delivered at desired time intervals by the use of time reference signals, e.g. clock signals
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
- H03K5/13—Arrangements having a single output and transforming input signals into pulses delivered at desired time intervals
- H03K5/14—Arrangements having a single output and transforming input signals into pulses delivered at desired time intervals by the use of delay lines
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/081—Details of the phase-locked loop provided with an additional controlled phase shifter
Definitions
- the present invention relates to a semiconductor memory device; and, more particularly, to a delay locked loop using a bi-directional ring oscillator and a counter unit.
- a delay locked loop (DLL) circuit reduces or compensates a skew between a clock signal and data or between an external clock and an internal clock, which is used in synchronizing an internal clock of a synchronous memory to an external clock without incurring any error.
- a timing delay is occurred when a clock provided externally is used within the apparatus.
- the delay locked loop controls the timing delay to synchronize the internal clock to the external clock.
- the synchronization between the internal and external clocks requires operations of compensating a jitter of the external clock with an internal delay locked loop, controlling a time delay unit such that a delay of the internal clock is less sensitive to noise introduced by a power supply or random noises, and fastening a locking time at maximum through the control of the time delay unit.
- a delay locked loop with a reduced jitter and an easily controllable time delay unit to overcome the foregoing requirements has been recently presented in ISSCC paper on 1999, entitled “A 250 Mb/s/pin 1 Gb Double Data Rate SDRAM with a Bi-Directional Delay and an Inter-Bank Shared Redundancy Scheme” by NEC Corporation.
- FIG. 1 is a connection diagram of a conventional linear bi-directional delay DLL proposed by NEC Corporation.
- the conventional DDL includes an input unit 100 , a first to a third D-flip flop 101 , 103 and 104 , an first inverter 102 , a dummy delay unit 105 , a first and a second AND gate 106 and 107 , a first and a second bi-directional delay block 108 and 109 , a first and a second pulse generation unit 110 and 111 , and an OR gate 112 .
- the input unit 100 receives a clock signal CLK and a non-clock signal CLKB via positive and negative terminals respectively and comparing received signals to produce a rising clock Rclk.
- the first D-flip flop 101 receives the rising clock Rclk as a clock signal and outputs a control signal with a pulse duration corresponding to one cycle of the rising clock Rclk.
- the first inverter 102 inverts the output of the first D-flip flop 101 to produce an inverted signal to be fed back as input to the first D-flip flop 101 .
- the second D-flip flop 103 receives the output of the first D-flip flop 101 and the rising clock Rclk from the input unit 100 and produces a first forward signal FWD_A having a pulse duration corresponding to one cycle of the output of the first D-flip flop 101 and a first backward signal BWD_A having an opposite phase to the first forward signal FWD_A.
- the third D-flip flop 104 receives an inverted value for the output of the first D-flip flop 101 and the rising clock Rclk, and produces a second forward signal FWD_B having a pulse duration corresponding to one cycle of the output of the first D-flip flop 101 and a second backward signal BWD_B having an opposite phase to the second forward signal FWD_B.
- the dummy delay unit 105 delays the rising clock Rclk by a skew to compensate the clock signal CLK.
- the first AND gate 106 logically combines the outputs of the second D-flip flop 103 and the dummy delay unit 105 to produce a combined output.
- the second AND gate 107 logically combines the outputs of the third D-flip flop 104 and the dummy delay unit 105 to produce a combined output.
- the first bi-directional delay block 108 including a multiplicity of unit bi-directional delays which are connected serially, receives the output of the first AND gate 106 and controls a time delay in a first or second direction under the control of the first forward signal FWD_A and the first backward signal BWD_A.
- the second bi-directional delay block 109 including a multiplicity of unit bi-directional delays which are connected in series, receives the output of the second AND gate 107 and controls a time delay in the first or second direction under the control of the second forward signal FWD_B and the second backward signal BWD_B.
- the first pulse generation unit 110 generates a pulse at a rising and a falling edge of the output of the first bi-directional delay block 108 .
- the second pulse generation unit 111 generates a pulse at a rising and a falling edge of the output of the second bi-directional delay block 109 .
- the OR gate 112 performs an OR operation on the outputs of the first and second pulse generation units 110 and 111 .
- FIG. 2A is connection diagram of a conventional unit bi-directional delay, which has been proposed by FUJITSU Ltd.
- the unit bi-directional delay proposed by FUJITSU includes four three-phase buffers 200 , 201 and 203 .
- the first three-phase buffer 200 receives one of the outputs of the first and second AND gates as a first input signal A m to produce a second control signal B m , wherein the gate of a PMOS transistor is controlled by the first or second backward signal (hereinafter called BWD) and the gate of a NMOS transistor is controlled by the first or second forward signal (hereinafter called FWD).
- BWD first or second backward signal
- FWD first or second forward signal
- the second three-phase buffer 201 receives the second output signal B m , wherein the gate of a PMOS transistor is controlled by the BWD signal and the gate of a NMOS transistor is controlled by the FWD signal.
- the third three-phase buffer 202 receives the output of an unit bi-directional delay at a previous stage as a second input signal B m+1 , to produce a first output signal A m+1 , wherein the gate of a PMOS transistor is controlled by the backward signal BWD and the gate of a NMOS transistor is controlled by the forward signal FWD.
- the fourth three-phase buffer 203 receives the first output signal A m+1 to produce the second output signal B m , wherein the gate of a PMOS transistor is controlled by the forward signal FWD and the gate of a NMOS transistor is controlled by the backward signal BWD.
- the first and second three-phase buffers 200 and 201 are activated to provide input signal to the first direction (i.e., the forward direction).
- the forward signal FWD is logic low and the backward signal BWD is logic high
- the third and fourth three-phase buffers 202 and 203 are activated to provide input signal to the second direction (i.e., the backward direction).
- FIG. 2B is a symbolic diagram of the unit bi-directional delay shown in FIG. 2A.
- the construction and operation in FIG. 2B is similar that of the previously described in conjunction with FIG. 2A and therefore a further description thereof is omitted herein.
- FIG. 2C is a connection diagram of the unit bi-directional delay proposed by NEC Corporation.
- a difference between NEC and FUJITSU is that the PMOS transistor is removed in the first and fourth three-phase buffers 200 and 203 , and the NMOS transistor is removed in the second and third three-phase buffers 201 and 202 , preventing both of the first and second input signals A m and B m+1 with a logic low value from being transmitted to corresponding buffers.
- the construction of the delay locked loop described above shows that generates a DDL signal at the rising clock Rclk of the clock signal CLK
- the construction for the rising clock Rclk is similar to that of a delay locked loop for outputting the DDL signal at the falling clock Fclk of the clock signal CLK except that the output signal of the input unit 100 is a falling clock.
- FIG. 3 is a timing diagram illustrating the operating principle of the first and second bi-directional delay blocks.
- the logic high of the second output signal B 0 _A means that all the backward nodes have been rendered to logic high and also all the forward nodes have been rendered to logic low. In short, a reset operation may be automatically performed for subsequent processes without any reset operation.
- the delay locked loop may be implemented with the bi-directional delay.
- the interval t clk -t m increases with an increase in one clock cycle t clk , so that a length of the bi-directional delay line should be lengthened by an increased interval. That is, many unit bi-directional delays are additionally required.
- the first and second bi-directional delay blocks 108 and 109 of the delay locked loop shown in FIG. 1 include 40 stages of unit bi-directional delays to adjust a time delay in low frequency applications, and four control signal lines to be used in controlling each of the unit bi-directional delays.
- the prior art places greater chip area requirements, which, in turn, may decrease the number of an wafer net die, thereby leading to increase in cost for the apparatus.
- a delay locked loop for use in a semiconductor memory device, which comprises: an input unit for receiving a clock signal and a non-clock signal and comparing received signals to produce an internal clock signal; a controller for receiving the internal clock to produce a first forward signal and a second backward signal each having a pulse duration corresponding to one cycle of the clock signal, a first backward signal and a second forward signal each having an opposite phase to the first forward signal and the second backward signal, and a first and a second start signal each having a pulse duration corresponding to a time delay to be compensated; a bi-directional oscillator, responsive to the second forward signal, the second backward signal and the second start signal, perform a ring oscillation in a first or second direction and fulfilling an addition and subtraction adjustment function for a time delay; a counter for receiving an output signal of the bi-directional oscillator, and counting the number that the output signal is passed therethrough; and an output means for performing a combination
- the present invention employs only four-stages of unit bi-directional delay block and a three-bits counter to allow an operation to be performed up to 40 MHz in frequency. Also, the present invention employs only four-stages of unit bi-directional delay block and a four-bits counter to allow the operation to be performed up to 20 MHz in frequency. Accordingly, the present invention has the ability to implement a delay locked loop with a reduced layout requirement even at a low frequency 25 MHz corresponding to a wafer test frequency.
- FIG. 1 shows a connection diagram of a conventional linear bi-directional delay DLL proposed by NEC Corporation
- FIG. 2A is connection diagram of a conventional unit bi-directional delay which has been proposed by FUJITSU Ltd.;
- FIG. 2B is a symbolic diagram of the unit bi-directional delay shown in FIG. 2A;
- FIG. 2C is a connection diagram of the unit bi-directional delay proposed by NEC Corporation.
- FIG. 3 is a timing diagram illustrating the operating principle of the first and second bi-directional delay blocks
- FIG. 4 is a connection diagram of a delay locked loop in accordance with preferred embodiments of the present invention.
- FIG. 5 is a timing diagram illustrating a flow of control signals outputted from the controller 410 of the present invention.
- FIG. 6A is a block diagram showing that an unit bi-directional inverter is inserted at the linear bi-directional delays
- FIG. 6B is a schematic block diagram illustrating the principle of the bi-directional ring oscillator 421 in accordance with a preferred embodiment of the present invention.
- FIG. 7A is a connection diagram of the unit bi-directional delay 426 in a first stage in accordance with the present invention.
- FIG. 7B is a symbolic diagram of the unit bi-directional delay shown in FIG. 7A in accordance with the present invention.
- FIG. 8A is a connection diagram of the unit bi-directional inverter 429 of present invention.
- FIG. 8B is a connection diagram in which three unit bi-directional inverters are connected in series for simulation.
- FIG. 9 is a timing diagram of signal waveforms in accordance with the present invention.
- FIG. 4 There is shown in FIG. 4 a connection diagram of a delay locked loop in accordance with preferred embodiments of the present invention.
- the delay locked loop of the present invention comprises an input unit 400 , a controller 410 , a first and a second bi-directional delay blocks 420 and 430 , and an OR gate 440 .
- the input unit 400 receives a clock signal CLK and a non-clock signal CLKB and compares received signals to produce a rising clock Rclk.
- the controller 410 receives the rising clock Rclk as a clock signal, and outputs a first forward signal FWD_A and a second backward signal BWD_A each having a pulse duration corresponding to one cycle of the clock signal CLK, a first backward signal BWD_A and a second forward signal FWD_B each having an opposite phase to the first forward signal FWD_A and the second backward signal BWD_B, and a first and a second start signals START_A and START_B each having a pulse duration corresponding to a time delay to be compensated.
- the first bi-directional delay block 420 which includes a bi-directional ring oscillator and a counter unit, receives the first forward signal FWD_A, the first backward signal BWD_A and the first start signal START_A from the controller 410 to perform an addition and subtraction adjustment function for a time delay.
- the second bi-directional delay block 430 which includes a bi-directional ring oscillator and a counter unit, receives the second forward signal FWD_B, the second backward signal BWD_B and the second start signal START_B from the controller 410 to perform an addition and subtraction adjustment function for a time delay.
- the OR gate 440 performs an OR operation on the outputs of the first and second bi-directional delay blocks 420 and 430 , to generate the result as a final rising clock Rclk_DLL.
- the controller 410 includes a first to third D-flip flops 411 , 412 and 414 , a dummy delay unit 413 , and a first and a second AND gates 415 and 416 .
- the first D-flip flop 411 receives the rising clock Rclk as a clock signal to produce a first forward signal FWD_A having a pulse duration corresponding to one cycle of the clock signal CLK and a first backward signal BWD_A having an opposite phase to the first forward signal FWD_A.
- the second D-flip flop 412 receives the rising clock Rclk as a clock signal to produce a second forward signal FWD_B having a pulse duration corresponding to one cycle of the clock signal CLK and a second backward signal BWD_B having an opposite phase to the second forward signal FWD_B.
- the dummy delay unit 413 delays the rising clock Rclk by a skew to compensate the clock signal CLK.
- the third D-flip flop 414 receives the output of the dummy delay unit 413 as a clock signal to produce a first delay rising clock Rclk_A and a second delay rising clock Rclk_B having an opposite phase to the first delay rising clock Rclk_A.
- the first AND gate 415 logically combines the first delay rising clock Rclk_A and the first forward signal FWD_A to produce a combined output.
- the second AND gate 416 logically combines the second delay rising clock Rclk_B and the second forward signal FWD_B to produce a combined output.
- the first bi-directional delay block 420 includes a bi-directional ring oscillator 421 , a forward counter 422 , a backward counter 423 , a counter comparator 424 and an AND gate 425 .
- the bi-directional ring oscillator 421 receives the first start signal START_A and to perform a ring oscillation in a first and a second directions.
- the bi-directional ring oscillator 421 receives the first start signal START A to perform a ring oscillation in a first and a second direction.
- the forward counter 422 receives a forward loop signal from the bi-directional ring oscillator 421 to count the number of the oscillations.
- the backward counter 423 receives a backward loop signal from the bi-directional oscillator 421 to count the number of the oscillations.
- the counter comparator 424 compares the outputs of the forward counter 422 and the backward counter 423 to determine if the outputs (i.e., counted numbers) are identical each other.
- the AND gate 425 logically combines the outputs of the bi-directional ring oscillator 421 and the counter comparator 424 to produce a combined value.
- a simplified bi-directional ring oscillator has the capacity to function as the multi-stages of delay line formed by unit bi-directional delays in the prior art.
- the construction of the second bi-directional delay block 430 is similar to that of the first bi-directional delay block 420 except that the second start signal START_B is fed to the bi-directional ring oscillator.
- the bi-directional ring oscillator 421 includes three unit bi-directional delays 426 , 427 and 428 , and a bi-directional inverter 429 .
- the unit bi-directional delays 426 , 427 and 428 which are connected in series, receives a first output signal A 0 _A from the bi-directional inverter 429 to output the forward loop signal in the first direction, and receives the backward loop signal from the bi-directional inverter 429 to output a second output signal B 0 _A in the second direction, under the control of the first start signal START_A, the first forward signal FWD_A and the first backward signal BWD_A.
- the bi-directional inverter 429 receives the forward loop signal to output the first output signal A 0 _A in the first direction and receives the second output signal B 0 _A to produce the backward loop signal in the second direction, under the control of the first forward signal FWD_A and the first backward signal BWD_A.
- FIG. 5 is a timing diagram illustrating a flow of control signals outputted from the controller 410 of the present invention.
- the first forward signal FWD_A and the first backward signal BWD_A are out-of-phase and two cycle signals, and similarly the second forward signal FWD_B and the second backward signal BWD_B are out-of-phase and two cycle signals. Accordingly, the first forward signal FWD_A and the second backward signal BWD_B are identical and the first backward signal BWD_A and the second forward signal FWD_B are identical.
- the first and second delay rising clocks Rclk_A and Rclk_B are a signal reflecting a dummy delay (t dm in FIG. 4).
- the rising of the first start signal START A is controlled by the first delay rising clock Rclk_A and the falling thereof is controlled by the first forward signal FWD A.
- the first and second bi-directional delay units 420 and 430 have the same structure and alternatively operate every one cycle.
- the delay locked loop In operation, the delay locked loop generates a clock preceding by the compensation skew t dm for an external clock, wherein t dm is a fixed value ranging several nanoseconds. Accordingly, these delay locked loops are common to measure the interval between t clk and t dm and delay a clock by a measured interval.
- FIG. 6A is a block diagram showing that an unit bi-directional inverter is inserted at the linear bi-directional delays.
- the inverting operation of the unit bi-directional inverter allows a logic low and a logic high to be alternatively rendered to thereby transmit a corresponding signal via an unit delay line.
- the bi-directional delay unit is indicated by a white block and the bi-directional inverter is indicated by a black block.
- the overall operation of FIG. 6A is similar to that of the linear bi-directional delay discussed above, except that a phase of the signal is inverted each occasion that it is passed through the unit bi-directional inverter. That is, a delay to a backward direction may be occurred in correspondence to a time proceeded to a forward direction.
- FIG. 6A shows that the signal is periodically passed through the unit bi-directional inverter, so FIG. 6A is contemplated as FIG. 6B as will be explained below.
- FIG. 6B is a schematic block diagram illustrating the principle of the bi-directional ring oscillator 421 in accordance with a preferred embodiment of the present invention.
- the bi-directional ring oscillator 421 includes a plurality of unit bi-directional delays and the bi-directional inverter which are connected in a ring fashion, and two counter. Each of the counters serves to count the number that a signal is rounded through the ring oscillator.
- a simplified bi-directional ring oscillator has the ability to act as the conventional bi-directional delay with a long length.
- the present invention requires only one bi-directional inverter, a very small number of unit bi-directional delays and two counters, thereby drastically reducing chip area requirements and covering even in low frequency applications (i.e., a larger clock cycle), while maintaining the merits of the linear bi-directional delay block. Further, since the bi-directional ring oscillator oscillates its own, what is need is a reset operation before that the first start signal START_A is inputted.
- FIG. 7A is a connection diagram of the unit bi-directional delay 426 in a first stage in accordance with the present invention.
- the unit bi-directional delay 426 used in the present invention includes a first to a fourth three-phase buffer 700 , 710 , 720 and 730 , and a PMOS transistor 740 .
- the first three-phase buffer 700 receives the output of an unit bi-directional delay in the previous stage to produce a second output signal B m , wherein the gate of a PMOS transistor is controlled by the first and second backward signals (BWD) and the gate of a NMOS transistor is controlled by the first and second forward signals (FWD) and the first and second start signals (START) for applying a start input to the bi-directional ring oscillator line forming a ring.
- the second three-phase buffer 710 receives the second output signal B m to produce a first output signal A m+1 , wherein the gate of a PMOS transistor is controlled by the backward signal BWD and the gate of a NMOS transistor is controlled by the forward signal FWD.
- the third three-phase buffer 730 receives the output of the unit bi-directional delay in the previous stage to produce a first output signal A m+1 , wherein the gate of a PMOS transistor is controlled by the forward signal FWD and the gate of a NMOS transistor is controlled by the backward signal BWD.
- the fourth three-phase buffer 720 receives the first output signal A m+1 to produce the second output signal B m , wherein the gate of a PMOS transistor is controlled by the forward signal FWD and the gate of a NMOS transistor is controlled by the backward signal BWD.
- the gate of the PMOS transistor 740 receives the first and second start signals START_A and START_B, and its source and drain are formed between a line input voltage and the second output signal B m .
- FIG. 7B is a symbolic diagram of the unit bi-directional delay shown in FIG. 7A in accordance with the present invention.
- FIG. 7B a configuration in which the inverters diametrically opposite each other is similar to that of the unit bi-directional delay proposed by FUJITSU Ltd., except that the PMOS transistor 740 is added for a reset operation.
- FIG. 8A is a connection diagram of the unit bi-directional inverter 429 of present invention.
- the unit bi-directional inverter 429 of the present invention includes a first and a second three-phase buffer 800 and 810 .
- the first three-phase buffer 800 receives the first output signal A m of the unit bi-directional delay in the previous stage to produce a forward loop signal and the second output signals A m+1 and B m , wherein the gate of a PMOS transistor is controlled by the backward signal BWD and the gate of a NMOS transistor is controlled by the forward signal FWD.
- the second three-phase buffer 810 receives a backward loop signal of the unit bi-directional delay in the previous stage to produce the second output signal A m+1 and the forward loop signal B m .
- FIG. 8B is a connection diagram in which three unit bi-directional inverters are connected in series for simulation.
- FIG. 9 is a timing diagram of signal waveforms in accordance with a preferred embodiment of the present invention.
- the forward signal FWD is rendered to logic high and a reset signal “Resetb” is rendered to logic low for prior to the start signal “Start” being inputted, then the bi-directional ring oscillator is reset. If the start signal “Start” is rendered to logic high, the signal is transmitted in a first direction, and the forward counter 422 counts the number of rising edges of the transmitted signal based on a forward loop signal A 3 .
- the signal is conversely transmitted to allow the backward counter to be activated.
- the counter comparator 424 compares the outputs of the backward counter and the forward counter and produces a counter match signal “count_match” with a logic high value if the outputs are equal each other. According to the counter match signal “count_match”, rising edges of the output signal B 0 of the bi-directional ring oscillator is outputted as a final rising clock Rclk_DLL. Since one bi-directional ring oscillator produces one DDL clock every two clock cycle, obtainment of one DDL clock per each clock cycle requires an additional bi-directional ring oscillator.
- the present invention employs a bi-directional ring oscillator, a forward counter and a backward counter to thereby reduce chip area requirements in contrast with the prior art delay locked loop and operate in low frequency applications, which, in turn, achieve a fast locking and a reduced jitter.
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Abstract
Description
- The present invention relates to a semiconductor memory device; and, more particularly, to a delay locked loop using a bi-directional ring oscillator and a counter unit.
- In general, a delay locked loop (DLL) circuit reduces or compensates a skew between a clock signal and data or between an external clock and an internal clock, which is used in synchronizing an internal clock of a synchronous memory to an external clock without incurring any error. Typically, a timing delay is occurred when a clock provided externally is used within the apparatus. The delay locked loop controls the timing delay to synchronize the internal clock to the external clock.
- The synchronization between the internal and external clocks requires operations of compensating a jitter of the external clock with an internal delay locked loop, controlling a time delay unit such that a delay of the internal clock is less sensitive to noise introduced by a power supply or random noises, and fastening a locking time at maximum through the control of the time delay unit. A delay locked loop with a reduced jitter and an easily controllable time delay unit to overcome the foregoing requirements has been recently presented in ISSCC paper on 1999, entitled “A 250 Mb/s/
pin 1 Gb Double Data Rate SDRAM with a Bi-Directional Delay and an Inter-Bank Shared Redundancy Scheme” by NEC Corporation. - FIG. 1 is a connection diagram of a conventional linear bi-directional delay DLL proposed by NEC Corporation.
- Referring to FIG. 1, the conventional DDL includes an
input unit 100, a first to a third D-flip flop 101, 103 and 104, anfirst inverter 102, adummy delay unit 105, a first and asecond AND gate bi-directional delay block pulse generation unit 110 and 111, and anOR gate 112. - The
input unit 100 receives a clock signal CLK and a non-clock signal CLKB via positive and negative terminals respectively and comparing received signals to produce a rising clock Rclk. The first D-flip flop 101 receives the rising clock Rclk as a clock signal and outputs a control signal with a pulse duration corresponding to one cycle of the rising clock Rclk. Thefirst inverter 102 inverts the output of the first D-flip flop 101 to produce an inverted signal to be fed back as input to the first D-flip flop 101. The second D-flip flop 103 receives the output of the first D-flip flop 101 and the rising clock Rclk from theinput unit 100 and produces a first forward signal FWD_A having a pulse duration corresponding to one cycle of the output of the first D-flip flop 101 and a first backward signal BWD_A having an opposite phase to the first forward signal FWD_A. The third D-flip flop 104 receives an inverted value for the output of the first D-flip flop 101 and the rising clock Rclk, and produces a second forward signal FWD_B having a pulse duration corresponding to one cycle of the output of the first D-flip flop 101 and a second backward signal BWD_B having an opposite phase to the second forward signal FWD_B. - The
dummy delay unit 105 delays the rising clock Rclk by a skew to compensate the clock signal CLK. The first ANDgate 106 logically combines the outputs of the second D-flip flop 103 and thedummy delay unit 105 to produce a combined output. The second ANDgate 107 logically combines the outputs of the third D-flip flop 104 and thedummy delay unit 105 to produce a combined output. - The first
bi-directional delay block 108 including a multiplicity of unit bi-directional delays which are connected serially, receives the output of thefirst AND gate 106 and controls a time delay in a first or second direction under the control of the first forward signal FWD_A and the first backward signal BWD_A. - The second
bi-directional delay block 109 including a multiplicity of unit bi-directional delays which are connected in series, receives the output of the second ANDgate 107 and controls a time delay in the first or second direction under the control of the second forward signal FWD_B and the second backward signal BWD_B. - The first
pulse generation unit 110 generates a pulse at a rising and a falling edge of the output of the firstbi-directional delay block 108. The second pulse generation unit 111 generates a pulse at a rising and a falling edge of the output of the secondbi-directional delay block 109. The ORgate 112 performs an OR operation on the outputs of the first and secondpulse generation units 110 and 111. - FIG. 2A is connection diagram of a conventional unit bi-directional delay, which has been proposed by FUJITSU Ltd.
- As shown in FIG. 2A, the unit bi-directional delay proposed by FUJITSU includes four three-
phase buffers - The first three-
phase buffer 200 receives one of the outputs of the first and second AND gates as a first input signal Am to produce a second control signal Bm, wherein the gate of a PMOS transistor is controlled by the first or second backward signal (hereinafter called BWD) and the gate of a NMOS transistor is controlled by the first or second forward signal (hereinafter called FWD). The second three-phase buffer 201 receives the second output signal Bm, wherein the gate of a PMOS transistor is controlled by the BWD signal and the gate of a NMOS transistor is controlled by the FWD signal. - The third three-
phase buffer 202 receives the output of an unit bi-directional delay at a previous stage as a second input signal Bm+1, to produce a first output signal Am+1, wherein the gate of a PMOS transistor is controlled by the backward signal BWD and the gate of a NMOS transistor is controlled by the forward signal FWD. - The fourth three-
phase buffer 203 receives the first output signal Am+1 to produce the second output signal Bm, wherein the gate of a PMOS transistor is controlled by the forward signal FWD and the gate of a NMOS transistor is controlled by the backward signal BWD. - When the forward signal FWD is logic high and the backward signal BWD is logic low, the first and second three-
phase buffers phase buffers - FIG. 2B is a symbolic diagram of the unit bi-directional delay shown in FIG. 2A. The construction and operation in FIG. 2B is similar that of the previously described in conjunction with FIG. 2A and therefore a further description thereof is omitted herein.
- FIG. 2C is a connection diagram of the unit bi-directional delay proposed by NEC Corporation.
- As shown in FIG. 2C, a difference between NEC and FUJITSU is that the PMOS transistor is removed in the first and fourth three-
phase buffers phase buffers - Although the construction of the delay locked loop described above shows that generates a DDL signal at the rising clock Rclk of the clock signal CLK, the construction for the rising clock Rclk is similar to that of a delay locked loop for outputting the DDL signal at the falling clock Fclk of the clock signal CLK except that the output signal of the
input unit 100 is a falling clock. - FIG. 3 is a timing diagram illustrating the operating principle of the first and second bi-directional delay blocks.
- Referring to FIG. 3, in case the first forward signal FWD_A is logic high and the first backward signal BWD_A is logic low, when the first output signal A0_A is rendered to a logic high after a compensation skew tdm, the logic high signal A0-A is propagated to the first direction (i.e., the forward direction). In this case, it requires a prior condition that all the forward nodes (Am_A, m=0, 1, 2, . . . , 40) should be set to logic low and all the backward nodes (Bm_B, m=0, 1, 2, . . . , 40) should be set to logic high. Since rendering of the forward node to logic high allows the backward node corresponding thereto to be rendered to logic low, it is necessary to set the backward node to logic low till a position to which the logic high is transmitted.
- Thereafter, if the first forward signal FWD_A is rendered to a logic low and the first backward signal BWD_A is rendered to a logic high, at the same time that the logic high signal is propagated to the second direction (i.e., the backward direction) to thereby render the first output signal B0_A to a logic high after an interval tclk-tdm, wherein tclk is one clock cycle. That is, the signal preceding by tdm from a rising edge of a subsequent clock. As mentioned above, since a signal preceding by tdm per two cycles may be obtained, an additional bi-directional delay line is provided and both of the delay lines are alternatively operated, allowing a DDL clock to be obtained at each cycle. The logic high of the second output signal B0_A means that all the backward nodes have been rendered to logic high and also all the forward nodes have been rendered to logic low. In short, a reset operation may be automatically performed for subsequent processes without any reset operation.
- The delay locked loop may be implemented with the bi-directional delay. However, in low frequency applications, the interval tclk-tm increases with an increase in one clock cycle tclk, so that a length of the bi-directional delay line should be lengthened by an increased interval. That is, many unit bi-directional delays are additionally required.
- The first and second
bi-directional delay blocks - Accordingly, the prior art places greater chip area requirements, which, in turn, may decrease the number of an wafer net die, thereby leading to increase in cost for the apparatus.
- It is, therefore, a primary object of the present invention to provide a delay locked loop, which is capable of achieving a reduced jitter and a stable time delay adjustment, to thereby perform a bi-directional time delay with a small area even at low frequency applications.
- In accordance with a preferred embodiment of the present invention, there is provided a delay locked loop for use in a semiconductor memory device, which comprises: an input unit for receiving a clock signal and a non-clock signal and comparing received signals to produce an internal clock signal; a controller for receiving the internal clock to produce a first forward signal and a second backward signal each having a pulse duration corresponding to one cycle of the clock signal, a first backward signal and a second forward signal each having an opposite phase to the first forward signal and the second backward signal, and a first and a second start signal each having a pulse duration corresponding to a time delay to be compensated; a bi-directional oscillator, responsive to the second forward signal, the second backward signal and the second start signal, perform a ring oscillation in a first or second direction and fulfilling an addition and subtraction adjustment function for a time delay; a counter for receiving an output signal of the bi-directional oscillator, and counting the number that the output signal is passed therethrough; and an output means for performing a combination operation on the outputs of the bi-directional oscillator and the counter, to produce the result as a final internal clock signal.
- By changing a linear structure into a ring structure, the present invention employs only four-stages of unit bi-directional delay block and a three-bits counter to allow an operation to be performed up to 40 MHz in frequency. Also, the present invention employs only four-stages of unit bi-directional delay block and a four-bits counter to allow the operation to be performed up to 20 MHz in frequency. Accordingly, the present invention has the ability to implement a delay locked loop with a reduced layout requirement even at a low frequency 25 MHz corresponding to a wafer test frequency.
- The above and other objects and features of the present invention will become apparent from the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which:
- FIG. 1 shows a connection diagram of a conventional linear bi-directional delay DLL proposed by NEC Corporation;
- FIG. 2A is connection diagram of a conventional unit bi-directional delay which has been proposed by FUJITSU Ltd.;
- FIG. 2B is a symbolic diagram of the unit bi-directional delay shown in FIG. 2A;
- FIG. 2C is a connection diagram of the unit bi-directional delay proposed by NEC Corporation;
- FIG. 3 is a timing diagram illustrating the operating principle of the first and second bi-directional delay blocks;
- FIG. 4 is a connection diagram of a delay locked loop in accordance with preferred embodiments of the present invention;
- FIG. 5 is a timing diagram illustrating a flow of control signals outputted from the
controller 410 of the present invention; - FIG. 6A is a block diagram showing that an unit bi-directional inverter is inserted at the linear bi-directional delays;
- FIG. 6B is a schematic block diagram illustrating the principle of the
bi-directional ring oscillator 421 in accordance with a preferred embodiment of the present invention; - FIG. 7A is a connection diagram of the unit
bi-directional delay 426 in a first stage in accordance with the present invention; - FIG. 7B is a symbolic diagram of the unit bi-directional delay shown in FIG. 7A in accordance with the present invention;
- FIG. 8A is a connection diagram of the unit
bi-directional inverter 429 of present invention; - FIG. 8B is a connection diagram in which three unit bi-directional inverters are connected in series for simulation; and
- FIG. 9 is a timing diagram of signal waveforms in accordance with the present invention.
- There is shown in FIG. 4 a connection diagram of a delay locked loop in accordance with preferred embodiments of the present invention.
- As shown in FIG. 4, the delay locked loop of the present invention comprises an
input unit 400, acontroller 410, a first and a second bi-directional delay blocks 420 and 430, and anOR gate 440. - The
input unit 400 receives a clock signal CLK and a non-clock signal CLKB and compares received signals to produce a rising clock Rclk. Thecontroller 410 receives the rising clock Rclk as a clock signal, and outputs a first forward signal FWD_A and a second backward signal BWD_A each having a pulse duration corresponding to one cycle of the clock signal CLK, a first backward signal BWD_A and a second forward signal FWD_B each having an opposite phase to the first forward signal FWD_A and the second backward signal BWD_B, and a first and a second start signals START_A and START_B each having a pulse duration corresponding to a time delay to be compensated. - The first
bi-directional delay block 420, which includes a bi-directional ring oscillator and a counter unit, receives the first forward signal FWD_A, the first backward signal BWD_A and the first start signal START_A from thecontroller 410 to perform an addition and subtraction adjustment function for a time delay. Similarly, the secondbi-directional delay block 430, which includes a bi-directional ring oscillator and a counter unit, receives the second forward signal FWD_B, the second backward signal BWD_B and the second start signal START_B from thecontroller 410 to perform an addition and subtraction adjustment function for a time delay. The ORgate 440 performs an OR operation on the outputs of the first and second bi-directional delay blocks 420 and 430, to generate the result as a final rising clock Rclk_DLL. - The
controller 410 includes a first to third D-flip flops dummy delay unit 413, and a first and a second ANDgates - The first D-
flip flop 411 receives the rising clock Rclk as a clock signal to produce a first forward signal FWD_A having a pulse duration corresponding to one cycle of the clock signal CLK and a first backward signal BWD_A having an opposite phase to the first forward signal FWD_A. The second D-flip flop 412 receives the rising clock Rclk as a clock signal to produce a second forward signal FWD_B having a pulse duration corresponding to one cycle of the clock signal CLK and a second backward signal BWD_B having an opposite phase to the second forward signal FWD_B. - The
dummy delay unit 413 delays the rising clock Rclk by a skew to compensate the clock signal CLK. The third D-flip flop 414 receives the output of thedummy delay unit 413 as a clock signal to produce a first delay rising clock Rclk_A and a second delay rising clock Rclk_B having an opposite phase to the first delay rising clock Rclk_A. The first ANDgate 415 logically combines the first delay rising clock Rclk_A and the first forward signal FWD_A to produce a combined output. The second ANDgate 416 logically combines the second delay rising clock Rclk_B and the second forward signal FWD_B to produce a combined output. - The first
bi-directional delay block 420 includes abi-directional ring oscillator 421, aforward counter 422, abackward counter 423, acounter comparator 424 and an ANDgate 425. Thebi-directional ring oscillator 421 receives the first start signal START_A and to perform a ring oscillation in a first and a second directions. - Specifically, the
bi-directional ring oscillator 421 receives the first start signal START A to perform a ring oscillation in a first and a second direction. Theforward counter 422 receives a forward loop signal from thebi-directional ring oscillator 421 to count the number of the oscillations. Thebackward counter 423 receives a backward loop signal from thebi-directional oscillator 421 to count the number of the oscillations. Thecounter comparator 424 compares the outputs of theforward counter 422 and thebackward counter 423 to determine if the outputs (i.e., counted numbers) are identical each other. The ANDgate 425 logically combines the outputs of thebi-directional ring oscillator 421 and thecounter comparator 424 to produce a combined value. - By the afore-mentioned construction, a simplified bi-directional ring oscillator has the capacity to function as the multi-stages of delay line formed by unit bi-directional delays in the prior art.
- The construction of the second
bi-directional delay block 430 is similar to that of the firstbi-directional delay block 420 except that the second start signal START_B is fed to the bi-directional ring oscillator. - The
bi-directional ring oscillator 421 includes three unitbi-directional delays bi-directional inverter 429. The unitbi-directional delays bi-directional inverter 429 to output the forward loop signal in the first direction, and receives the backward loop signal from thebi-directional inverter 429 to output a second output signal B0_A in the second direction, under the control of the first start signal START_A, the first forward signal FWD_A and the first backward signal BWD_A. Thebi-directional inverter 429 receives the forward loop signal to output the first output signal A0_A in the first direction and receives the second output signal B0_A to produce the backward loop signal in the second direction, under the control of the first forward signal FWD_A and the first backward signal BWD_A. - FIG. 5 is a timing diagram illustrating a flow of control signals outputted from the
controller 410 of the present invention. - Referring to FIG. 5, in the
controller 410 of the present invention, the first forward signal FWD_A and the first backward signal BWD_A are out-of-phase and two cycle signals, and similarly the second forward signal FWD_B and the second backward signal BWD_B are out-of-phase and two cycle signals. Accordingly, the first forward signal FWD_A and the second backward signal BWD_B are identical and the first backward signal BWD_A and the second forward signal FWD_B are identical. The first and second delay rising clocks Rclk_A and Rclk_B are a signal reflecting a dummy delay (tdm in FIG. 4). The rising of the first start signal START A is controlled by the first delay rising clock Rclk_A and the falling thereof is controlled by the first forward signal FWD A. The first and secondbi-directional delay units - In operation, the delay locked loop generates a clock preceding by the compensation skew tdm for an external clock, wherein tdm is a fixed value ranging several nanoseconds. Accordingly, these delay locked loops are common to measure the interval between tclk and tdm and delay a clock by a measured interval.
- FIG. 6A is a block diagram showing that an unit bi-directional inverter is inserted at the linear bi-directional delays.
- Referring to FIG. 6A, the inverting operation of the unit bi-directional inverter allows a logic low and a logic high to be alternatively rendered to thereby transmit a corresponding signal via an unit delay line. In FIG. 6A, the bi-directional delay unit is indicated by a white block and the bi-directional inverter is indicated by a black block. The overall operation of FIG. 6A is similar to that of the linear bi-directional delay discussed above, except that a phase of the signal is inverted each occasion that it is passed through the unit bi-directional inverter. That is, a delay to a backward direction may be occurred in correspondence to a time proceeded to a forward direction. FIG. 6A shows that the signal is periodically passed through the unit bi-directional inverter, so FIG. 6A is contemplated as FIG. 6B as will be explained below.
- FIG. 6B is a schematic block diagram illustrating the principle of the
bi-directional ring oscillator 421 in accordance with a preferred embodiment of the present invention. - Referring to FIG. 6B, the
bi-directional ring oscillator 421 includes a plurality of unit bi-directional delays and the bi-directional inverter which are connected in a ring fashion, and two counter. Each of the counters serves to count the number that a signal is rounded through the ring oscillator. By constructing as the above, a simplified bi-directional ring oscillator has the ability to act as the conventional bi-directional delay with a long length. The present invention requires only one bi-directional inverter, a very small number of unit bi-directional delays and two counters, thereby drastically reducing chip area requirements and covering even in low frequency applications (i.e., a larger clock cycle), while maintaining the merits of the linear bi-directional delay block. Further, since the bi-directional ring oscillator oscillates its own, what is need is a reset operation before that the first start signal START_A is inputted. - FIG. 7A is a connection diagram of the unit
bi-directional delay 426 in a first stage in accordance with the present invention. - Referring to FIG. 7A, the unit
bi-directional delay 426 used in the present invention includes a first to a fourth three-phase buffer PMOS transistor 740. The first three-phase buffer 700 receives the output of an unit bi-directional delay in the previous stage to produce a second output signal Bm, wherein the gate of a PMOS transistor is controlled by the first and second backward signals (BWD) and the gate of a NMOS transistor is controlled by the first and second forward signals (FWD) and the first and second start signals (START) for applying a start input to the bi-directional ring oscillator line forming a ring. - The second three-
phase buffer 710 receives the second output signal Bm to produce a first output signal Am+1, wherein the gate of a PMOS transistor is controlled by the backward signal BWD and the gate of a NMOS transistor is controlled by the forward signal FWD. - The third three-
phase buffer 730 receives the output of the unit bi-directional delay in the previous stage to produce a first output signal Am+1, wherein the gate of a PMOS transistor is controlled by the forward signal FWD and the gate of a NMOS transistor is controlled by the backward signal BWD. - The fourth three-
phase buffer 720 receives the first output signal Am+1 to produce the second output signal Bm, wherein the gate of a PMOS transistor is controlled by the forward signal FWD and the gate of a NMOS transistor is controlled by the backward signal BWD. - The gate of the
PMOS transistor 740 receives the first and second start signals START_A and START_B, and its source and drain are formed between a line input voltage and the second output signal Bm. - FIG. 7B is a symbolic diagram of the unit bi-directional delay shown in FIG. 7A in accordance with the present invention.
- Referring to FIG. 7B, a configuration in which the inverters diametrically opposite each other is similar to that of the unit bi-directional delay proposed by FUJITSU Ltd., except that the
PMOS transistor 740 is added for a reset operation. - FIG. 8A is a connection diagram of the unit
bi-directional inverter 429 of present invention. - Referring to FIG. 8A, the unit
bi-directional inverter 429 of the present invention includes a first and a second three-phase buffer phase buffer 800 receives the first output signal Am of the unit bi-directional delay in the previous stage to produce a forward loop signal and the second output signals Am+1 and Bm, wherein the gate of a PMOS transistor is controlled by the backward signal BWD and the gate of a NMOS transistor is controlled by the forward signal FWD. The second three-phase buffer 810 receives a backward loop signal of the unit bi-directional delay in the previous stage to produce the second output signal Am+1 and the forward loop signal Bm. - FIG. 8B is a connection diagram in which three unit bi-directional inverters are connected in series for simulation.
- FIG. 9 is a timing diagram of signal waveforms in accordance with a preferred embodiment of the present invention.
- Referring to FIG. 9, if the forward signal FWD is rendered to logic high and a reset signal “Resetb” is rendered to logic low for prior to the start signal “Start” being inputted, then the bi-directional ring oscillator is reset. If the start signal “Start” is rendered to logic high, the signal is transmitted in a first direction, and the
forward counter 422 counts the number of rising edges of the transmitted signal based on a forward loop signal A3. - Alternatively, if the backward signal BWD is rendered to logic high, the signal is conversely transmitted to allow the backward counter to be activated. The
counter comparator 424 compares the outputs of the backward counter and the forward counter and produces a counter match signal “count_match” with a logic high value if the outputs are equal each other. According to the counter match signal “count_match”, rising edges of the output signal B0 of the bi-directional ring oscillator is outputted as a final rising clock Rclk_DLL. Since one bi-directional ring oscillator produces one DDL clock every two clock cycle, obtainment of one DDL clock per each clock cycle requires an additional bi-directional ring oscillator. - As mentioned above, the present invention employs a bi-directional ring oscillator, a forward counter and a backward counter to thereby reduce chip area requirements in contrast with the prior art delay locked loop and operate in low frequency applications, which, in turn, achieve a fast locking and a reduced jitter.
- Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims (13)
Applications Claiming Priority (3)
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KR99-62227 | 1999-12-24 | ||
KR1019990062227A KR100318431B1 (en) | 1999-12-24 | 1999-12-24 | A very compact Delay Locked Loop using bi-directional ring oscillator and counter |
KR1999-62227 | 1999-12-24 |
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US20010022745A1 true US20010022745A1 (en) | 2001-09-20 |
US6434062B2 US6434062B2 (en) | 2002-08-13 |
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US09/745,490 Expired - Lifetime US6434062B2 (en) | 1999-12-24 | 2000-12-21 | Delay locked loop for use in semiconductor memory device |
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US (1) | US6434062B2 (en) |
JP (1) | JP4378560B2 (en) |
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TW (1) | TW487923B (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050265238A1 (en) * | 2004-05-28 | 2005-12-01 | Matthew Mattina | Flow control method and apparatus for single packet arrival on a bidirectional ring interconnect |
US20060156081A1 (en) * | 2004-04-28 | 2006-07-13 | Infineon Technologies Ag | Semiconductor component test procedure, as well as a data buffer component |
US7230495B2 (en) | 2004-04-28 | 2007-06-12 | Micron Technology, Inc. | Phase-locked loop circuits with reduced lock time |
US10490242B2 (en) * | 2016-09-22 | 2019-11-26 | Qualcomm Incorporated | Apparatus and method of clock shaping for memory |
Families Citing this family (10)
Publication number | Priority date | Publication date | Assignee | Title |
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DE10223178B4 (en) * | 2002-05-24 | 2004-11-04 | Infineon Technologies Ag | Circuit arrangement with a sequence control, integrated memory and test arrangement with such a circuit arrangement |
JP3776847B2 (en) * | 2002-07-24 | 2006-05-17 | エルピーダメモリ株式会社 | Clock synchronization circuit and semiconductor device |
JP2004355081A (en) * | 2003-05-27 | 2004-12-16 | Internatl Business Mach Corp <Ibm> | Information processing device and memory module |
US7065001B2 (en) * | 2004-08-04 | 2006-06-20 | Micron Technology, Inc. | Method and apparatus for initialization of read latency tracking circuit in high-speed DRAM |
US7660187B2 (en) * | 2004-08-04 | 2010-02-09 | Micron Technology, Inc. | Method and apparatus for initialization of read latency tracking circuit in high-speed DRAM |
US7046060B1 (en) * | 2004-10-27 | 2006-05-16 | Infineon Technologies, Ag | Method and apparatus compensating for frequency drift in a delay locked loop |
KR100685604B1 (en) * | 2005-06-22 | 2007-02-22 | 주식회사 하이닉스반도체 | Delay locked loop for generating a internal clock signal with decreased jitter components |
KR100808052B1 (en) | 2005-09-28 | 2008-03-07 | 주식회사 하이닉스반도체 | Semicoductor memory device |
JP4775141B2 (en) | 2005-09-29 | 2011-09-21 | 株式会社ハイニックスセミコンダクター | Delay locked loop circuit |
US8710889B1 (en) * | 2010-09-22 | 2014-04-29 | Altera Corporation | Apparatus for controllable delay cell and associated methods |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
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JPH10173498A (en) | 1996-12-12 | 1998-06-26 | Mitsubishi Electric Corp | Variable delay circuit |
US6005904A (en) * | 1997-10-16 | 1999-12-21 | Oasis Design, Inc. | Phase-locked loop with protected output during instances when the phase-locked loop is unlocked |
-
1999
- 1999-12-24 KR KR1019990062227A patent/KR100318431B1/en not_active IP Right Cessation
-
2000
- 2000-12-21 US US09/745,490 patent/US6434062B2/en not_active Expired - Lifetime
- 2000-12-22 DE DE10064206.3A patent/DE10064206B4/en not_active Expired - Fee Related
- 2000-12-25 JP JP2000393046A patent/JP4378560B2/en not_active Expired - Fee Related
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060156081A1 (en) * | 2004-04-28 | 2006-07-13 | Infineon Technologies Ag | Semiconductor component test procedure, as well as a data buffer component |
US7230495B2 (en) | 2004-04-28 | 2007-06-12 | Micron Technology, Inc. | Phase-locked loop circuits with reduced lock time |
US20050265238A1 (en) * | 2004-05-28 | 2005-12-01 | Matthew Mattina | Flow control method and apparatus for single packet arrival on a bidirectional ring interconnect |
US7551564B2 (en) * | 2004-05-28 | 2009-06-23 | Intel Corporation | Flow control method and apparatus for single packet arrival on a bidirectional ring interconnect |
US10490242B2 (en) * | 2016-09-22 | 2019-11-26 | Qualcomm Incorporated | Apparatus and method of clock shaping for memory |
Also Published As
Publication number | Publication date |
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TW487923B (en) | 2002-05-21 |
DE10064206B4 (en) | 2018-03-29 |
US6434062B2 (en) | 2002-08-13 |
JP4378560B2 (en) | 2009-12-09 |
KR100318431B1 (en) | 2001-12-24 |
KR20010064096A (en) | 2001-07-09 |
DE10064206A1 (en) | 2001-07-26 |
JP2001251172A (en) | 2001-09-14 |
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