International Business Machines Corporation

Ilya I Novof

John E Gersbach

Frank David Ferraiolo

Ram Kelkar

Stephen Dale Wyatt

Joseph Kinman Lee

Donald E Strayer

James Lee Lentz

Steven Frederick Oakland

Charles Joseph Masenas

Charles R Hoffman

Roland A Bechade

John S Austin

Jeffery Howard Oppold

Masayuki Hayashi

Kenneth J Shaw

Leon Skarshinski

Richard F Keil

Kenneth Dean Short

Bruce Kaufmann

Jitter is controlled in a phase locked loop (PLL) adaptively and continuously in real time by a jitter control circuit. The jitter control circuit makes periodic PLL output jitter measurements and causes sequential measurements to be compared. The comparison provides an indication as to whether output jitter is being improved or degraded. Charge pump gains associated with internal parameters and external parameters that adversely affect output jitter are modified in response to the comparisons. If output jitter is adversely affected by an increment or decrement of one of the gain values, then the gain value is moved in the opposite direction. Output jitter is optimized for both gain values. Such optimization occurs during normal circuit operation and is continuous so as to adapt to changing conditions.

Phase locked loop having adaptive jitter reduction

A delay equalization circuit for minimizing the static phase error in a PLL is provided. The delay equalization circuit includes an external clock signal variable delay path, and an element for creating a pulse with a width proportional to the delay of the external clock signal variable delay path. The delay equalization circuit also includes a delay path in the feedback loop, and second element for creating a second pulse in proportion to the delay of the internal delay path. Finally, the circuit contains a comparison device. The comparison device compares the first and second pulses. The comparison device outputs a difference signal in proportion to the difference in the external and internal path delays. That difference signal is fed back and used to control the external path delay such that the external delay is driven to be substantially equal to the internal delay, minimizing the static phase error of the PLL device.

Delay equalization apparatus and method

A computer controlled odor mixing and dispensing system has an linear array of odorant containers arranged in an annular member. Each container is provided with a computer controlled metering delivery device which dispenses the odorant onto a rotating absorptive porus member. An air handling system forces air through the rotating member which mixes the odors deposited thereon and delivers the mixed odors to a user.

Computer controlled olfactory mixer and dispenser for use in multimedia

A protective circuit for a phase lock loop ensures that the VCO does not initiate a runaway condition when outputting a signal having a frequency higher than the feedback divider can respond to. During normal phase lock operation, a counter keeps track of the PLL input signal and is reset by the feedback divider. In the runaway condition the counter is not reset and triggers a control signal to the VCO. A second counter can be used to keep track of the feedback divider output and to reset the first counter. When the first counter far outruns the second counter the control signal is triggered.

Anti-latching mechanism for phase lock loops

A phase-lock indicator circuit is disclosed that compares first and second clock signals and indicates when the signals are in-phase. The circuit includes a phase-only detector which is immune to frequency differences. The clock signals are compared by first extracting their leading edges and generating a first pulse signal when the leading edges occur simultaneously. Then, when a consecutive number of first pulse signals has occurred, a second pulse signal is generated, which in turn produces a lock indication signal, indicating that the first clock signal is in-phase with the second clock signal, regardless of whether or not the frequencies of the clock signals are equal. The lock circuit can be used in any PLL circuit regardless of the specific Phase Detector used. The circuit can also be used in any application or circuit where two clocks need to be tracked. In addition, the phase-lock detector includes a loss of input clock feature that indicates if the input clock is lost.

Phase-lock indicator circuit with phase-only detection

A built-in system and method is provided that measures Phase Lock Loop (PLL) output clock error. An edge sorting circuit is utilized to measure jitter between corresponding transition edges of a measured clock and a reference clock, and then stores the value in an N bit word. A decoder circuit reads in the value and increments a corresponding counter. A state machine then reads the counters, processes the information and outputs one or more PLL clock error values.

Integrated circuit chip having built-in self measurement for PLL jitter

A frequency-lock indicator circuit is disclosed that compares first and second clock signals and indicates when the signals have the same frequencies for a consecutive number of times. The circuit includes a Frequency-Only Detector (FOD) which is immune to phase differences. The frequencies of the clock signals are compared through counters that will reset each other if a consecutive number of frequencies from the clock signals do not occur at the same time. Then, when a consecutive number of equal frequencies has occurred, a first pulse signal is generated, which in turn produces a lock indication signal, indicating that the first clock signal has the same frequency as the second clock signal, regardless of whether or not the phases of the clock signals are equal. The lock indicator circuit can be used in any PLL circuit regardless of the specific Frequency/Phase Detector used. The circuit can also be used in any application or circuit where two clocks need to be tracked. In addition, the FOD includes a loss of input clock feature that indicates if the input clock is lost.

Frequency-lock indicator circuit with frequency-only detection

An integrated current reference circuit provides a current output with a predetermined temperature coefficient, suitably zero, to provide constant current over temperature variations. The circuit is formed of only Field Effect Transistors (FETs), allowing the circuit to be implemented using conventional CMOS fabrication techniques. A current mirror provides a reference current in both branches of the circuit. The output of the current mirror is coupled to a circuit providing an imbalance in resistance between the two branches, and an offsetting imbalance in voltages between the two branches, resulting in a reference current that has a predetermined temperature coefficient. An output current is provided which is proportional to the reference current and thus has the same temperature coefficient as the reference current.

All FET fully integrated current reference circuit

A phase locked loop circuit is provided which includes a phase/frequency detector which uses a divider circuit and feedback from a clock distribution tree to generate INC and DEC pulses which do not have 'dead zones'. A pair of charge pumps receives the INC and DEC pulses. One charge pump is a differential pump and has a voltage controlled common mode feedback circuit to maintain a common mode controlled voltage. A differential current is outputted to a loop filter capacitor by this charge pump. The other charge pump is a single-ended output pump which supplies current to a current controlled oscillator which also receives input from a voltage to current converter. The current controlled oscillator includes a variable resistance load which varies inversely with the magnitude of the input current. A jitter control circuit is also provided which reduces jitter in the current controlled oscillator output in the locked phase. Also, a lock indicator is provided which is time independent, and provides a lock indication when the loop enters the locked condition.

Phase locked loop circuit with phase/frequency detector which eliminates

An improved configuration of a capacitor formed with FET technology and a resistor and/or conductor is provided. In this configuration a capacitor is formed in which the diffusion zone of the substrate is used as one plate of the capacitor and what would normally be the gate electrode of an FET is used as the other plate of the capacitor, with the two plates being separated by a conventional thin dielectric gate oxide layer. An insulator, such as silicon dioxide overlays the gate electrode, and electrical connections to the gate electrode and diffusion zone are made through the insulator to allow the two plates of the capacitor to be connected to various devices or components as required. The top surface of this insulation layer is also used to form metal resistors. Depending on the value of required resistance, a second insulating layer may be used and a second level of metal used to connect segments of the resistors formed on the first layer of metal to form a longer resistor. This second layer of metal may also be used to form inductors. Moreover both inductors and resistors can be formed; however this may require a third layer of metal for connection purposes.

Integrated compact capacitor-resistor/inductor configuration

A phase locked loop circuit includes a phase/frequency detector which uses a divider circuit and feedback from a clock distribution tree to generate INC and DEC pulses which have no 'dead zone'. A pair of charge pumps receives the INC and DEC pulses. One charge pump is a differential pump and has voltage controlled common mode feedback circuit to maintain a common mode controlled voltage. A differential current is outputted to a loop filter capacitor by this charge pump. The other charge pump is a single-ended output pump which supplies current to a current controlled oscillator which also receives input from a voltage to current converter. The current controlled oscillator includes a variable resistance load which varies inversely with the magnitude of the input current. A jitter control circuit is provided which reduces jitter in the current controlled oscillator output in the locked phase. Also, a lock indicator is provided which is time independent, and provides a lock indication when the loop enters the locked condition. The circuits for these components are described in detail.

Resistorless phase locked loop circuit employing direct current injection

A phase-controlled loop system having a charge pump circuit including a current mismatch measurement circuit and a current compensation circuit for equalizing the amplitude of positive current pulses and the amplitude of negative current pulses output when the phase-controlled loop system is in phase-locked condition. The current mismatch measurement circuit includes duplicate complementary current sources with characteristics and biasing substantially identical to that of the primary current sources providing the positive current and the negative current to the output node of the charge pump circuit. At the common connected node between the duplicate complementary current sources an error current is produced having an amplitude equal to the difference between the amplitude of the positive current pulses and the amplitude of the negative current pulses to the output node. Current mirrors then reflect this error current back to either the positive current source or the negative current source for combining with the positive current or negative current, respectively, such that the currents' amplitudes at the output node substantially cancel. Various current mismatch measurement circuit and current compensation circuit embodiments are described, including a time multiplexed sensing and compensation approach.

Charge pump circuit with symmetrical current output for phase-controlled

A phase locked loop circuit includes a phase/frequency detector which uses a divider circuit and feedback from a clock distribution tree to generate INC and DEC pulses which have no 'dead zone'. A pair of charge pumps receives the INC and DEC pulses. One charge pump is a differential pump and has voltage controlled common mode feedback circuit to maintain a common mode controlled voltage. A differential current is outputted to a loop filter capacitor by this charge pump. The other charge pump is a single-ended output pump which supplies current to a current controlled oscillator which also receives input from a voltage to current converter. The current controlled oscillator includes a variable resistance load which varies inversely with the magnitude of the input current. A jitter control circuit is provided which reduces jitter in the current controlled oscillator output in the locked phase. Also, a lock indicator is provided which is time independent, and provides a lock indication when the loop enters the locked condition.

Differential current controlled oscillator with variable load

Method and apparatus for reducing jitter in a phase locked loop circuit

A system and method is provided for estimating the bit error rate of a data signal which has been reconstructed from a received data signal. The system comprises (i) logic for determining timing degradation and amplitude degradation of the received data signal; (ii) an actual bit error rate calculator for calculating the actual bit error rate of the reconstructed data signal; (iii) an instantaneous bit error rate calculator for estimating a bit error rate of the reconstructed signal using the timing degradation and the amplitude degradation; (iv) a first integrator for integrating the estimated bit error rate; (v) a comparator for comparing the integrated estimated bit error rate with the actual bit error rate and outputting an error signal which modifies the estimated bit error rate; and (vi) a second integrator for integrating the estimated bit error rate. The time constant associated with the second integrator is shorter than the time constant associated with the first integrator.

Growing community of inventors

Essex Junction, VT, United States of America

Ilya I Novof