International Business Machines Corporation

Microsoft Technology Licensing, LLC

Qualcomm Incorporated

Globalfoundries U.S. 2 LLC

Minhan Chen

Ping Lu

Hayden C Cranford, Jr

Todd Morgan Rasmus

Kenneth Arcudia

Jieming Qi

Eugene R Atwood

Steven John Zier

Matthew B Baecher

William Richard Kelly

Hadi Goudarzi

Louis L Hsu

David William Boerstler

Louis Lu-Chen Hsu

Li Hsiang Sun

Michael Anthony Sorna

Zhi Zhu

Carrie Ellen Cox

Joseph Natonio

Karl David Selander

Shaishav A Desai

Steven Mark Clements

Bupesh Pandita

Eskinder Hailu

Jon Boyette

Westerfield John Ficken

Russell Deans

Chia Heng Chang

Yong Suk Jun

Kenneth Luis Arcudia

In a calibrated digital phase-locked-loop (DPLL) circuit, during a normal operating mode, a control value provided to a digitally controlled oscillator (DCO) is updated by a feedback circuit to keep an output clock generated by the DCO synchronized with a reference clock. The feedback circuit includes a time-to-digital converter (TDC) circuit to measure a phase difference as a time interval. In a calibration operating mode of the calibrated DPLL circuit, calibration of a resolution of a time measurement of the time interval measured by the TDC is performed in the feedback circuit while the control value provided to the DCO is kept constant. Calibrating the TDCs in each of the DPLLs in an integrated circuit (IC) to a nominal resolution in this manner improves synchronization of the clock domains. In some examples, the TDC circuit is a Vernier type circuit and calibration sets a delay difference to a nominal resolution.

Digital phase-locked loops (PLL) including closed-loop time-to-digital converter (TDC) gain calibration circuits and related methods

Time-to-digital converters (TDC) employing a single-stage delay pair for a wide input range and reduced quantization noise in a phase-locked loop (PLL) and related fabrication methods are disclosed. Aspects disclosed in the detailed description include a single-stage Vernier time-to-digital converter (TDC) which mitigates the device mismatch impact and therefore avoids possible spurious tones in a fractional-N PLL application. Combined with a delta-sigma noise shaping stage and a ring-oscillator based coarse TDC, the invention achieves a good trade-off between resolution, detection range and PLL locking speed.

Time-to-digital converters (TDC) employing a single-stage delay pair and noise shaping for wide input range and reduced quantization noise in a phase-locked loop (PLL)

A phase-interpolator (PI) circuit generates an interpolated clock to capture data in a capture circuit at a target phase in a phase range between two reference clocks based on an interpolation code within a range of interpolation codes is described. A clamping circuit coupled to the PI circuit provides an interpolation code within a reduced range, where the integral non-linearity (INL) of the interpolated clocks is below a threshold, such that data capture based on the interpolated clock has a lower bit error rate (BER). As a result, the interpolated clock is generated within a reduced phase range corresponding to the reduced range of interpolation codes. When a target phase for an interpolated clock is outside the reduced phase range, the clamping circuit may adjust the target phase clock relative to a reference clock to adjust the target phase to be within the reduced phase range for improved BER.

Phase interpolator (PI) with clamping circuit to limit operation to range having optimal integral non-linearity and related methods

A time-to-digital converter (TDC) circuit generates a digital output indicating a time, known as a phase difference, from a phase of the generated signal to a corresponding phase of a reference signal. The digital output is used by the digitally controlled oscillator (DCO) to correct for the phase/frequency difference to synchronize the generated signal with the reference signal. In an aspect, an adaptive TDC circuit generates a first digital indication in a coarse mode when the offset time is above a threshold and generates a second digital indication in a fine mode when the offset time is below the threshold. The first digital indication and the second digital indication each comprise a same number of bits, and the first digital indication is normalized to the second digital indication for the digital output of the adaptive TDC circuit. A fractional bit may be employed to compensate for a quantization error.

Time to digital converter (TDC) circuit with self-adaptive time granularity and related methods

In a calibrated phase-locked loop (PLL), a time-to-digital (TDC) converter circuit can be calibrated to a nominal gain by a calibration circuit to achieve a desired jitter response in the PLL. The TDC circuit in the PLL measures a time difference between the reference clock and a feedback signal as a number of time increments, and the calibration circuit adjusts a resolution of the measurement by adjusting the length of the time increments (i.e., resolution). In a Vernier method employed to measure the time difference, the length of a time increment is determined by a delay difference between a first delay of a first delay circuit in a first series of first delay circuits and a second delay of a second delay circuit in a second series of second delay circuits. Adjusting the resolution of the TDC circuit includes adjusting the delay difference between the first delay and the second delay.

Phase-locked loops (PLL), including time-to-digital converter (TDC) gain calibration circuits and related methods

A peak detector comprises multiple small-size amplitude detection circuits coupled in parallel to signal inputs at which a signal is received from a VCO. Each amplitude detection circuit generates a voltage on an output, indicating a voltage peak or amplitude of a first signal input and a second signal input (specifically, differential output of VCO). At a given time, only one small-size amplitude detection circuit is activated to load VCO, reducing the impact on LC resonant frequency. The plurality of small-size detection circuits work sequentially, and an automatic averaging of their outputs can significantly improve the peak detector fluctuation (caused by process variation and device mismatch) compared to each single small-size amplitude detection circuit.

Peak voltage amplitude detectors tolerant to process variation and device mismatch and related methods

Systems and methods related to calibrating a phase interpolator by amplifying timing differences are described. An example system includes a calibration stage configured to output a calibration code for a phase interpolator. The system further includes control logic configured to: (1) at least partially discharge a first pre-charged capacitive load in response to a signal output by the phase interpolator based on the calibration code, and (2) at least partially discharge a second pre-charged capacitive load in response to a reference signal associated with the phase interpolator. The system further includes a feedback path configured to provide feedback to the calibration stage to allow for a modification of the calibration code, where the feedback is dependent on a first voltage provided by the first pre-charged capacitive load and a second voltage provided by the second pre-charged capacitive load.

Calibrating a phase interpolator by amplifying timing differences

A receiver is provided that includes a time-to-digital converter for converting a phase difference between a clock signal and a received data signal into a phase-difference digital code. The receiver also includes a logic circuit that controls a programmable delay line to delay the clock signal into a delayed clock signal by a delay that is responsive to a difference between the phase-difference code and a unit interval for the clock signal. The delayed clock signal clocks a flip-flop to register the received data signal.

Low-power, low-latency time-to-digital-converter-based serial link

A receiver is provided that generates a data sampling clock that is offset by clock offset that is a function of a decision feedback equalizer gain to account for a data sampling timing error that would occur without the clock delay.

Receiver with cancellation of intrinsic offset from decision feedback equalization to enhance data margin

A resistor in a pair of resistors is selectively coupled to a current source through a selection switch during the reset phase of a voltage-mode sense amplifier so that one evaluation node for the voltage-mode sense amplifier is discharged from a power supply voltage by an ohmic voltage drop across the selectively-coupled resistor to null an offset for the voltage-mode sense amplifier.

Offset nulling for high-speed sense amplifier

Aspects of the disclosure are directed to determining an offset calibration step size of a sample latch. In accordance with one aspect, the disclosure relate to a Decision Feedback Equalizer (DFE) input section including a E sample latch to output a target signal sample; a E sample digital to analog converter coupled to the E sample latch to input a target voltage to the E sample latch; a sample latch to output a signal sample; and a voltage digital to analog converter coupled to the E sample latch and the sample latch to generate a bias voltage, wherein the bias voltage is inputted to the E sample latch and the sample latch. The DFE input section may further include a latch offset decoder to scale the bias voltage and a summing amplifier to receive an analog input waveform to the DFE input section.

Apparatus and method for calibrating a receiver with a decision feedback equalizer (DFE)

Systems and methods for providing offset calibration for low power and high performance receivers are described herein. In one embodiment, a receiver comprises a sample latch having a first input coupled to a receive data path, and a second input. The receive also comprises a first digital-to-analog converter (DAC), a second DAC, and a calibration controller. In a calibration mode, the calibration controller is configured to input a calibration voltage to the first input of the sample latch using the first DAC, to input a threshold voltage and an offset-cancelation voltage to the second input of the sample latch using the second DAC, to adjust the offset-cancelation voltage, to observe an output of the sample latch as the offset-cancelation voltage is adjusted, and to store a value of the offset-cancelation voltage at which a metastable state is observed at the output of the sample latch in a memory.

Offset calibration for low power and high performance receiver

A receiver according to one aspect comprises a latch configured to sample a data signal according to a sampling clock signal, and a plurality of offset-compensation segments, wherein each of the segments is coupled to an internal node of the latch. Each of the segments comprises a compensation transistor, and a step-adjustment transistor coupled in series with the compensation transistor. The receiver further comprises an offset controller configured to selectively turn on one or more of the compensations transistors to reduce an offset voltage of the latch, and a bias circuit configured to apply a bias voltage to a gate of each of one or more of the step-adjustment transistors.

Accurate sample latch offset compensation scheme

Dynamically calibrating an offset of a receiver with a DFE while performing data transport operations, the DFE comprising a plurality of independent data transport banks, at least one data transport bank operating a data transport mode and at least one data transport bank operating in a calibration mode, including: iteratively, while carrying out data transport operations: utilizing the data transport bank operating in the data transport mode to perform data transport operations; calibrating the data transport bank operating in the calibration mode; and upon completing calibration of the data transport bank operating in the calibration mode, switching the mode of each data transport bank.

Dynamically calibrating the offset of a receiver with a decision feedback equalizer (DFE) while performing data transport operations

Systems and methods for providing offset calibration for low power and high performance receivers are described herein. In one embodiment, a method for offset calibration comprises inputting a first voltage to a first input of a sample latch, and inputting a second voltage and an offset-cancellation voltage to a second input of the sample latch. The method also comprises adjusting the offset-cancellation voltage, observing an output of the sample latch as the offset-cancellation voltage is adjusted, and recording a value of the offset-cancellation voltage at which a metastable state is observed at the output of the sample latch. The method may be performed for each one of a plurality of different voltage levels for the first voltage to determine an offset-cancellation voltage for each one of the voltage levels.

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Cary, NC, United States of America

Minhan Chen