Lattice Semiconductor Corporation

Agere Systems Inc.

Richard Booth

Phillip Johnson

Paulius Mosinskis

Barry Britton

Yang Xu

Donald Dazzo, Jr

Tawei David Li

Zheng Chen

Parag Parikh

Roger L Minear

David Onimus

Paulius Mosinkis

In one embodiment, multiple (serializer-deserializer) SERDES channels are aligned by selectively slipping one or more of the incoming serial data streams one bit at a time prior to deserialization. Within each SERDES channel, a slip circuit slips the corresponding serial data stream by one bit (i.e., one unit interval (UI)) by extending the high portion of the duty cycle of a corresponding clock signal. The high portion of the clock signal is extended using a 3-to-1 mux that selects a fixed high signal, such as the high power supply rail, as an intermediate mux output signal whenever transitioning between two different applied clock signals that are offset from one another by one UI. In this way, the slip circuit avoids glitches that might otherwise result from switching directly between the two clock signals.

Delaying data signals

A phase locked loop (PLL) circuit is provided with selectable feedback paths. In one example, a method of operating a device includes passing a clock signal provided by a PLL circuit of the device through an internal feedback path of the PLL circuit to provide a first input signal to the PLL circuit while at least one external circuit of an external feedback path of the device is disabled during a low power operation mode of the device. The method also includes detecting a lock between the first input signal and a reference signal during the low power operation mode. The lock indicates that the clock signal is operating at a frequency used during a normal operation mode of the device. The method also includes passing the clock signal through the external feedback path to provide a second input signal to the PLL circuit. The method also includes switching from detecting a lock between the first input signal and the reference signal to detecting a lock between the second input signal and the reference signal if the external circuit is enabled for the normal operation mode.

Phase locked loop circuit with selectable feedback paths

In one embodiment, multiple (serializer/deserializer) SERDES channels are aligned by selectively slipping one or more of the incoming serial data streams one bit at a time prior to deserialization. Within each SERDES channel, a slip circuit slips the corresponding serial data stream by one bit (i.e., one unit interval (UI)) by extending the high portion of the duty cycle of a corresponding clock signal. The high portion of the clock signal is extended using a 3-to-1 mux that selects a fixed high signal, such as the high power supply rail, as an intermediate mux output signal whenever transitioning between two different applied clock signals that are offset from one another by one UI. In this way, the slip circuit avoids glitches that might otherwise result from switching directly between the two clock signals.

Techniques are provided to reduce glitches at an output signal node when a device is switched to and from a low power operation mode. In one example, a method of operating a device includes providing power to operate a signal source of the device during a normal operation mode of the device. The method also includes passing an output signal from the signal source through a signal path to an output node during the normal operation mode. The method also includes receiving an operation mode signal to switch the device from the normal operation mode to a low power operation mode. The method also includes disabling the signal path to prevent glitches from appearing at the output node during the switch from the normal operation mode to the low power operation mode. The method also includes continuing providing power to the signal source until after the signal path is disabled.

Power control block with output glitch protection

In one embodiment, a combined VGA-and-equalizer (VGA-EQ) circuit for a communication link includes a current-mode logic ('CML') amplifier with an inductive load circuit. The CML amplifier has a gain control terminal and is operable to amplify, with an adjustable gain, a signal received at an input terminal and provide the amplified signal at an output terminal. The CML amplifier has a first gain at frequencies below a predetermined frequency value and a second gain at frequencies in a predetermined frequency range above the predetermined frequency value, wherein the second gain is higher than the first gain. The higher second gain of the VGA-EQ circuit causes a reduction in inter-symbol interference in a signal received by the receiver.

Combined variable gain amplifier and analog equalizer circuit

In an exemplary decision-feedback equalizer (DFE) of a serializer/deserializer (SerDes) receiver, a single current mirror array is shared by multiple current digital-to-analog converter (IDAC) functions. The DFE has an initial amplifier stage that applies an initial coefficient COEFFto an input data signal and a number of (e.g., five) additional amplifier stages that apply additional coefficients (e.g., COEFF-COEFF) to different delayed versions of the recovered output data stream. The outputs of the initial and multiple additional amplifier stages are summed to generate an equalized data signal that is applied to a clock-and-data recovery (CDR) circuit. Due to certain characteristics of the equalizer function, the multiple additional amplifier stages can be implemented using a single shared current mirror array, which save significant amounts of chip area compared to conventional implementations in which each additional amplifier stage has its own dedicated current mirror array.

Shared-array multiple-output digital-to-analog converter

In one embodiment, the invention can be a clock-generating circuit having one or more clock-processing circuits, each outputting a clock signal having an adjustable phase. Each clock-processing circuit comprises a divider and a divisor control circuit. Each divider divides an input clock signal by a respective divisor value and outputs a corresponding output clock signal whose period is determined by the divisor value and the period of the input clock signal. Each divider receives the respective divisor value from the corresponding divisor control circuit, wherein the divisor value is selected in order to achieve a desired frequency and phase for the corresponding output clock signal. Temporarily changing a divisor value can advance or delay the phase of the corresponding output clock signal without having to reset the divider.

Dynamic delay or advance adjustment of oscillating signal phase

Systems and methods are disclosed herein to provide improved I/O techniques. For example, in accordance with an embodiment of the present invention, an integrated circuit includes a driver that receives data signals and provides an output signal based on the data signals, with the driver having a plurality of transistors with a first set of the plurality of transistors adapted to provide a first logical value as the output signal and a second set of the plurality of transistors adapted to provide a second logical value as the output signal based on the data signals. A sequencing circuit provides the data signals to the driver such that the first set of the plurality of transistors is switched on before the second set of the plurality of transistors is switched off, and the second set of the plurality of transistors is switched on before the first set of the plurality of transistors is switched off.

Switch sequencing circuit systems and methods

A cross-fill metal fill pattern technique is provided such that portions of a metal fill pattern are patterned to accomplish a secondary function. For instance, in the exemplary embodiments, ever other trace or line of interdigitated fingers is routed to a ground, while the interceding traces or lines of interdigitated fingers are routed to a power supply. In this way, a capacitor function is formed across the power supply, providing additional decoupling for the power supply. Moreover, a suitably tight cross-fill metal fill pattern (i.e., higher density of metal) provides an electrical shielding function for electromagnetic radiation passing therethrough.

Cross-fill pattern for metal fill levels, power supply filtering, and analog circuit shielding

A signal generator circuit includes a controller adapted to generate a divide value in accordance with at least a first control signal, and a divider adapted to divide an output signal of the signal generator circuit by the divisor value. The controller is selectively operable in at least one of a plurality of modes in accordance with at least a second control signal. The controller is configured to calculate each of one or more new divide values so as to vary a frequency of the output signal in accordance with at least one of the first and second control signals. The controller is configured to switch between operational modes and/or switch between divide values, the switching between operational modes and/or divide values being performed in such a manner so as to substantially eliminate discontinuities in the frequency of the output signal.

Signal generator with selectable mode control

An integrated circuit including at least one loop filter for use in a phase-locked loop, the loop filter including a resistive element and at least one metal-oxide-semiconductor (MOS) transistor configured as a capacitor having a first capacitance associated therewith. The MOS transistor is connected between a voltage source and an input of the loop filter via the resistive element. The loop filter further includes a bias circuit connected to the MOS transistor. The bias circuit is configured for maintaining a substantially constant reference voltage across the MOS transistor, the reference voltage being selected so as to bias the MOS transistor in a designated region of operation. In this manner, the first capacitance is substantially optimized per unit area.

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Riegelsville, PA, United States of America

Richard Booth