Altera Corporation

Sean Shau-Tu Lu

Yan Chong

Joseph Huang

Chiakang Sung

Pradeep Nagarajan

Warren Nordyke

Khai Nguyen

Kyung Suk Oh

Bonnie I Wang

Weiqi Ding

Gordon Raymond Chiu

Ee Mei Ooi

Weizhong Xu

Kin Hong Au

Chiakang Song

A method of measuring duty-cycle distortion in a signal (e.g., flowing between an operating circuit and a memory circuit), where the signal has a known period, the signal being measured is in a first state during a first portion of the period, and is in a different state during a second portion of the period, includes advancing or retarding the signal until an edge of the signal intersects an edge of the other signal. From the amount of the advancing or retarding, the duty cycle and the magnitude of duty-cycle distortion are determined. This may be used to control correction of the duty-cycle distortion. An interpolator circuit may be used to advance or retard the signal. A processor may be used to keep track of the amount of advancing or retarding, to determine the duration of the duty cycle, and control correction of the duty-cycle distortion.

Circuitry and methods for measuring and correcting duty-cycle distortion

An integrated circuit such as a programmable integrated circuit may include input-output circuits each having respective memory controller circuitry. The memory controller circuitry of the input-output circuits may be electrically coupled via a backbone path and configured to collectively form a memory controller. Each memory controller circuitry may include a protocol control circuit and input-output lanes. Memory access requests from on-chip circuitry may be provided to only a selected input-output circuit. The protocol control circuit of the selected input-output circuit may receive the memory access requests and generate memory control signals and local control signals from the memory access requests. The memory control signals may be provided to external memory. The local control signals may be provided to input-output circuits over the backbone path and synchronize the input-output circuits in conveying data between the integrated circuit and the external memory.

Integrated circuits having input-output circuits with dedicated memory controller circuitry

Integrated circuits may include memory interface circuitry that communicates with memory. The memory interface circuitry may include latch circuitry that receives a data strobe enable signal from the memory controller and latches the data strobe enable signal using a data strobe signal received from the memory. The integrated circuit may include logic circuitry that gates the data strobe signal using the latched data strobe enable signal. The logic circuitry may pass the data strobe signal in response to activation of the latched data strobe enable signal. The integrated circuit may include counter circuitry that monitors the gated data strobe signal. The counter circuitry may monitor the gated data strobe signal by counting pulses in the gated data strobe signal to produce a counter value. When the counter value reaches a target value, the logic circuitry may block the data strobe signal from passing to the memory controller.

Memory interface circuitry with improved timing margins

Systems and methods are disclosed for calibrating a Data Strobe (DQS) enable/disable signal and for tracking the timing of the DQS enable/disable signal with respect to changes in voltage and temperature (VT) in order to improve the timing margin of the DQS enable/disable signal in programmable devices using Double Data Rate (DDR) memory. In an exemplary embodiment, the system includes a gating circuit, a sampling circuit, and a delay chain tracking circuit. The gating circuit receives a DQS enable signal and a input DQS signal, calibrates the DQS enable signal based on an amount of delay, and outputs the calibrated DQS signal. The sampling circuit provides the amount of delay to the gating circuit based on a sampling clock. The delay chain tracking circuit maintains the timing of the calibrated DQS enable signal over a plurality of clock cycles based on the sampling clock and a leveling clock.

Circuit design technique for DQS enable/disable calibration

A circuit-includes a delay locked loop (DLL), a calibration circuit and an output delay chain controlled by the calibration circuit. The DLL comprises a plurality of series-coupled first delay elements, each of which has substantially the same first delay. The calibration circuit comprises a plurality of series-coupled second delay elements, each of which has substantially the same second delay that is less than the first delay, a first delay element, and a circuit for determining the minimum number of second delay elements that are needed to produce the first delay. The output delay chain comprises a plurality of series-coupled second delay elements, an input for receiving the input signal, and a circuit for selectively tapping the output delay chain at a plurality of taps in the output delay chain so as to produce in the input signal different delays of integral multiples of the second delay.

Digital PVT compensation for delay chain

Clock alignment circuitry may include phase comparator circuitry with a first input terminal that receives as first clock signal from a first clock tree and a second input terminal that receives a second clock signal from a second clock tree. The phase comparator circuitry may compare the first and second clock signals and generate different control signals based on the first and second clock signals. The integrated circuit may further include phase interpolator circuitry that generates an output clock signal based on at least one of the control signals received from the phase comparator circuitry. Edges of the generated output clock signal may align with edges of either the first clock signal or the second clock signal.

Methods and apparatus for clock tree phase alignment

An integrated circuit includes a clock circuit that may be used to provide clock signals to multiple input-output circuits. The integrated circuit may also include different clock structures. As an example, one of the clock structures may have multiple clock paths of substantially equal lengths while another clock structure may have a fly-by clock path. The multiple clock paths may be used to convey a subset of the clock signals to the input-output circuits. Similarly, the fly-by clock path may be used to transmit a second subset of the clock signals to the input-output circuits.

Clock structure with calibration circuitry

A circuit includes a delay locked loop (DLL), a calibration circuit and an output delay chain controlled by the calibration circuit. The DLL comprises a plurality of series-coupled first delay elements each of which has substantially the same first delay. The calibration circuit comprises a plurality of series-coupled second delay elements, each of which has substantially the same second delay that is less than the first delay, a first delay element, and a circuit for determining the minimum number of second delay elements that are needed to produce the first delay. The output delay chain comprises a plurality of series-coupled second delay elements, an input for receiving the input signal, and a circuit for selectively tapping the output delay chain at a plurality of taps in the output delay chain so as to produce in the input signal different delays of integral multiples of the second delay.

Integrated circuits may include memory interface circuitry operable to communicate with system memory. The memory interface circuitry may receive data and data strobe signals from system memory during read operations. The memory interface circuitry may include de-skew circuitry and dynamic variation compensation circuitry. The de-skew circuitry may be configured during calibration procedures to reduce skew between the data and data strobe signals. The dynamic variation compensation circuitry may be used in real time to compensate for variations in operating conditions. The dynamic variation compensation circuitry may include a phase generation circuit operable to generate data strobe signals having different phases, an edge detection circuit operable to detect leading/trailing edge failures, a control circuit operable to control a counter, and an adjustable delay circuit that is controlled by the counter and that is operable to properly position the data signal with respect to its corresponding data strobe signal.

Variation compensation circuitry for memory interface

A circuit includes a locked loop and a phase offset circuit. The locked loop generates first control signals for controlling a first delay in the locked loop. The phase offset circuit delays an input signal by a second delay that is controlled by second control signals to generate a delayed signal. The phase offset circuit generates the second control signals by adjusting the first control signals to increase the accuracy of the delayed signal with respect to a target phase. The second control signals compensate for at least a portion of a change in the second delay that is caused by a variation in at least one of a process, a supply voltage, and a temperature of the circuit.

Techniques for generating PVT compensated phase offset to improve accuracy of a locked loop

Digitally controlled delay-locked loops can have a phase detector, control logic, and a delay chain. The control logic generates digital signals in response to an output signal of the phase detector. The delay chain generates a delay that varies in response to the digital signals. In some embodiments, the control logic maintains logic states of the digital signals constant in response to an enable signal to maintain the delay of the delay chain constant in a lock mode of the digitally controlled delay-locked loop. In other embodiments, the delay of the delay chain varies by a discrete time period in response to a change in logic states of the digital signals, and the maximum phase error between a phase of the reference clock signal and a phase of the feedback clock signal is less than the discrete time period when the digitally controlled delay-locked loop is in a lock mode.

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San Jose, CA, United States of America

Sean Shau-Tu Lu