Snowbush Inc.

Agere Systems Inc.

Tony Pialis

Mehrdad Ramezani

Kenneth William Martin

Jonathan E Rogers

Raj Mahadevan

A phase lockedcircuit comprising a phase detector for comparing an incoming serial data signal with a feedback clock signal and generating a digital phase detector output signal representing a phase difference between the incoming data signal and the feedback clock signal; a dual path filter for receiving the phase detector output signal, the dual path filter including a first path for generating a digital proportional output signal that is proportional to the phase detector output signal and a second path having an integral digital filter for generating a digital integral output signal that is proportional to an integral of the phase detector output signal; and a digitally controlled oscillator for receiving the proportional output signal and the integral output signal as tuning inputs and generating in dependence thereon an output clock signal from which the feedback clock signal is obtained. The circuit can be implemented in a receive path of a serializer/deserializer.

Serializer deserializer circuits

A duty-cycle correction (DCC) circuit adapted to adjust the duty cycle of a differential clock signal to conform it to the requirements of a half-rate clocking system. In a representative embodiment, the DCC circuit has a buffer circuit adapted to generate a differential output clock signal by adding offset voltage to a differential input clock signal. A feedback loop coupled to the buffer circuit processes the output clock signal to evaluate deviation of its duty-cycle value from 50% and, based on the evaluation, configures the buffer circuit to adjust the offset voltage such that the duty-cycle deviation is reduced. The feedback loop and the buffer circuit are controlled by a duty-cycle calibration engine, e.g., a digital logic circuit adapted to determine an appropriate value for the offset voltage, which causes the duty-cycle value in the output clock signal to be substantially 50% regardless of the duty-cycle value in the input clock signal. As a result, technological limitations in the circuit-fabrication process do not significantly reduce the yield of chips for half-rate clocking systems.

Growing community of inventors

Toronto, Canada

Tony Pialis