International Business Machines Corporation

Elenion Technologies, LLC

Daihyun Lim

Marcel A Kossel

Pradeep Thiagarajan

Alexander V Rylyakov

Christian I Menolfi

Abdelrahman Ahmed

Ariel Leonardo Vera Villarroel

Within a modulator driver, different blocks are employed, e.g. a buffer, one or more variable gain amplifiers (VGA), and a final driver stage. Each of these blocks has an optimum bias point for best performance; however, interconnecting the blocks requires sharing the DC bias points in their interface, which does not necessarily match the optimum performance bias point of each block. Accordingly, a first offset feedback loop extending from reference points after a selected one of the blocks to an input of one of the blocks. The first offset feedback loop includes current sources capable of delivering a variable current to the input of the selected block in order to compensate any offset in an amplified differential input electrical signal measured at the reference points. A first bias feedback loop is also provided, including a current sinker for subtracting excess current introduced in the first offset compensation feedback loop.

Dual loop bias circuit with offset compensation

The invention relates to a multi-phase oscillator for generating multiple phase-shifted oscillator signals including: a ring oscillator having a number of concatenated oscillator delay cells which are interconnected to generate an oscillator signal, wherein phase-shifted oscillator signals are generated between the oscillator delay cells; a phase-blending unit configured to receive two phase-shifted oscillator signals and to generate a mid-phase oscillator signal whose phase shift is between the shifts of the two phase-shifted oscillator signals; and an interpolator delay line having a number of concatenated interpolator delay cells to generate further phase-shifted oscillator signals.

Voltage-controlled ring oscillator with delay line

An apparatus for encoding data signals includes a transmitter configured to encode and transmit a data signal over a communication channel, the transmitter including a precoder; a signal shaper configured to adjust the data signal by applying an equalization setting to the data signal, the equalization setting including an amplitude and offset and transmit the adjusted data signal to the precoder; and a processing unit. The processing unit is configured to perform: receiving channel coefficients associated with the communication channel; for each of a plurality of amplitude settings and a plurality of offset settings, calculating whether a modulo amplitude level would occur at a receiver using a modulo operation; selecting the equalization setting from the plurality of amplitude settings and the plurality of offset settings based on the calculation; and transmitting a control signal specifying the equalization setting to the signal shaper.

Precoding loss reduction

A slew rate controller for a computing system includes a slew rate control module, the slew rate control module further comprising a plurality of sampling modules, each sampling module corresponding to one of a plurality of phase signal inputs, wherein each sampling module receives an input signal, a reference voltage, and the sampling module's respective phase signal input, and wherein each sampling module generates a respective sample of a relationship between the input signal and the reference voltage during a time period indicated by the sampling module's respective phase signal input; and a finite state machine configured to output a slew rate control signal to control a slew rate of the input signal based on the plurality of samples from the sampling modules.

Closed-loop multiphase slew rate controller for signal drive in a computer system

A method and circuit for implementing a level shifter with built-in-logic function for reduced delay. The circuit including at least one set of inputs from a first power supply domain. The circuit further including at least two cross coupled field effect transistors (FETs) connected to a second power supply domain. The circuit further including a true logic gate connected to the first power supply domain and the at least two cross coupled FETs. The true logic gate being configured to generate a logic function based on the at least one set of inputs. The circuit further including a complementary logic gate connected to the first power supply domain and the at least two cross coupled FETs. The complementary logic gate being configured to generate a complement of the logic function based on the at least one set of inputs.

Level shifter with built-in logic function for reduced delay

A phase rotator based on voltage referencing is disclosed. A voltage signal is generated that is proportional to the phase difference between two input signals. The voltage signal is then used as the upper voltage limit for a digital-to-analog converter (DAC). The DAC is programmable via an input vector to generate a DAC output. The DAC output is used to generate a phase rotated (phase shifted) output, which is at an intermediate phase between the two input signals.

Phase rotator based on voltage referencing

Aspects of the invention provide for equalizing rise and fall slew rates at an output for a buffer. In one embodiment, a method includes: measuring, simultaneously, rise and fall slew rates at an input of the buffer and rise and fall slew rates at the output of the buffer; generating a slew reference based on at least one of the rise slew rate or the fall slew rate at the input of the buffer; comparing the rise slew rate and the fall slew rate at the output of the buffer to the slew reference; and generating at least one of a rise control signal or a fall control signal for adjusting at least one of the rise slew rate or the fall slew rate at the output of the buffer.

Equalized rise and fall slew rates for a buffer

A slew rate control circuit generates a slew-rate controlled clock signal from an input clock signal based on a feedback control mechanism. The feedback control mechanism uses the input clock signal duty cycle characteristics as a reference for controlling and maintaining an optimum slew rate for the slew-rate controlled clock signal. By using the input clock signal as a reference, the slew-rate controlled clock signal is dynamically measured and periodically adjusted over each cycle of the input clock signal.

Closed-loop slew-rate control for phase interpolator optimization

A method for startup and operation of an output stage of a transmitter, the output stage comprising a first protection field effect transistor (FET) and a second protection FET includes enabling a startup circuit; providing a first bias voltage to the first protection FET in the output stage and a second bias voltage to the second protection FET stage in the output stage by the startup circuit; disabling the startup circuit and enabling a protection voltage generator; providing the first bias voltage to the first protection FET in the output stage by the protection voltage generator; and providing the second bias voltage to the second protection FET in the output stage by a second bias voltage power supply.

Startup and protection circuitry for thin oxide output stage

A phase rotator includes a phase selector stage operative to receive a clock signal and output a first phase and a second phase of the clock signal, a slew rate control stage including a first pass gate circuit operative to control a slew rate of the first phase of the clock signal and a second pass gate circuit operative to control a slew rate of the second phase of the clock signal, and a phase blending stage operative to combine the first phase with the second phase of the clock signal and output a phase rotated signal.

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Edgewater, NJ, United States of America

Daihyun Lim