Cselt-Centro Studi E Laboratori Telecomunicazioni S.p.a.

Telecom Italia Lab S.p.a.

Marco Burzio

Emanuele Balistreri

Paolo Pellegrino

Bruno Bostica

Luca Pesando

A charge pump (,) is supplied to reset in rated conditions the error signal of a phase-locked loop of the type whereby a phase detector (,) periodically supplies this pump (,) with a first and second impulse having emission instants dependent on the phase ratio between phase-locked loop input signals and are allocated to control circuit output increase or decrease respectively by means of ring filter (,). The pump features loops (,) to transform the first and second impulse into a first and second voltage signal of longer duration than maximum impulse duration and featuring values the difference of which depends on the phase ratio between the loop input signals and to generate a signal in a current representative of such difference.

Integrated circuit phase-locked loop charge pump

A phase locked loop circuit includes an input comparator (,) capable of generating a deviation signal which can be used for driving an oscillator (,) so as to generate an output signal (CLKOUT) locked to the input signal. The oscillator (,) can operate according to a plurality of characteristics under the control of a control circuit (,) including searching circuits arranged to carry out a first search phase by scanning the family of characteristics admitted for the operation of the oscillator (,) by bands of progressively reduced width, according to a general, dichotomic procedure. Upon completion of this first search phase, additional circuits of fine search are destined to identify the optimum operating point, compensating possible fluctuations of the characteristics.

PLL having circuits for selecting optimum VCO input/output characteristics

The delay element consists of a differential amplifier (M,, M,, M,, M,, M,) in which the load transistors (M,, M,) are associated to respective gate biasing transistors (M,, M,) connected in a source follower configuration, and to feedback transistors (M,, M,), which implement a negative impedance in parallel to a positive impedance represented by each of the load transistors (M,, M,). The modulation of the delay is achieved by modulating the bias currents of the load transistors (M,, M,), the feedback transistors (M,. M,) and the gate biasing transistors (M,, M,).

High tunability CMOS delay element

A device (DC) is provided for compensating process and operating parameters variations in a CMOS integrated circuit. The device comprises means (CP, CT) for generating a first and a second compensation signals which depend on quality indexes of the fabrication process of the P and N transistors of the integrated circuit and on the operating temperature, and which are capable of compensating deviations of the controlled quantity from the desired value, due to the deviation of the quality indexes and temperature, respectively, from a typical value which would originate the desired value for the output parameter. The compensating device also can be implemented in the form of CMOS integrated circuit, preferably jointly with the device (OS) to be subjected to compensation (FIG.,).

Device for compensating process and operating parameter variations in CMOS integrated circuits

A current reference generator comprises a pair of identical units (G1, G2) which generate respective current references (I1, I2), and a circuit (CL) for the linear combination of the two references. In each of the two units, the elements (S1, S2) which, by their current-voltage characteristics, determine the working point comprise respectively a single transistor (T1) and a pair of transistors (T2, T3), of the same type as the first, connected in series. A differential amplifier (AD) maintains stable the working point of the respective unit as power supply voltage varies. (FIG. 2)

CMOS circuit for generating a current reference, the circuit comprising

A phase locked loop (1) including an oscillator (5), usually made as a voltage controlled oscillator (VCO), arranged to operate selectively according to different input/output characteristics. The circuit further includes a control circuit (81) for selectively controlling the operation of the oscillator (5) thereby making the oscillator (5) itself operate on one of an optimum characteristic selectively determined according to the operating conditions of the loop (1).

Phase locked loop having control circuit for automatically operating VCO

A device and a method for aligning in time two essentially isochronous digital signals are provided, in which a plurality (2.sup.n) of replicas (CK1-CK4) of the first signal (CKIN), separated by a given phase difference, are generated and a number of said replicas (CK3, CK4) is subjected to sampling (4, 5) in correspondence with the rising edges of the second signal (DATA). As the result of the sampling, a combination of logic signals (SL0, SL1) is obtained which is representative of the phase relation existing between each of said replicas (CK1-CK4) and the second signal (DATA). The output signal (CKOUT) of the device, aligned with the second signal, corresponds to the one, among the replicas (CK1-CK4) of the first signal, which best reproduces the desired alignment condition.

Device for and method of aligning in time digital signals, for example a

A circuit source has bias and modulation current generators for both p-type and n-type optical sources, and a pair of sources of control voltages for the bias and modulation current generators, which obtain pairs of control voltages from an adjustable driving current. An external signal allows selecting, by means of a control logic and CMOS gates, the generators required by the source. The circuit is made by using three pads of an integrated circuit, one for each control voltage source and the third comprising the current generators, the CMOS gates and the control logic.

Circuit in CMOS technology for high speed driving of optical sources

The serializing-parallelizing circuit comprises, on a single integrated circuit chip (IC), a transmitter (TX) which performs the parallel-to-series conversion of the data stream, the insertion into the serial stream, with a pre-set periodicity, of a synchronism word, and the line coding of the serial stream, and a receiver (RX) in which clock signals synchronous with the data stream are extracted from a serial stream of coded data and in which the data are decoded and the decoded signals undergo series-to-parallel conversion. The transmitter (TX) and the receiver (RX) can be configured to operate with 4 or 8-bit parallelism.

Serializing-parallelizing circuit for high speed digital signals

The circuit for clock signal extraction from a high speed data stream which allows a rapid attainment of the identity between the frequencies of the locally generated clock signal and of the data signal, even when such frequencies are very different. The circuit can easily be inserted into a more complex CMOS digital integrated circuit, it has low power dissipation and is capable of operating at bit rates exceeding 300 Mbit/s. The circuit has a main phase locked loop, which controls a voltage controlled oscillator by continually controlling its phase and a secondary loop, which allows the main loop to become locked, by causing the voltage controlled oscillator to oscillate at a frequency close to the operating frequency.

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Turin, Italy

Marco Burzio