Abstract: A phase locked loop is provided that includes a phase comparator, a charge pump circuit, a loop filter, and a voltage controlled oscillator. The charge pump circuit includes two symmetric branches, feedback paths, and circuit breaking switches. Each of the symmetric branches has a constant current generator and a pulsed current generator, with one terminal of the loop filter being connected to one of the symmetric branches and the other terminal of the loop filter being connected to the other of the symmetric branches. The feedback paths control the constant current generators based on voltages at the terminals of the loop filter, and each of the circuit breaking switches couple one of the pulsed current generators and the corresponding terminal of the loop filter. The pulsed current generators supply a first current whose amplitude is proportional to an amplitude of a second current supplied by the constant current generators through the duty cycle of the first current.

Abstract: A method of assessing the offset on the output nodes of an amplifying channel includes generating a logic signal for signaling the existence of an offset having a level exceeding a window of permitted levels symmetric about the zero level. The window is defined by a negative limit value and by a positive limit value. The method includes establishing an interval or phase of detection by applying to an input of a detection circuit a timing pulse with a certain frequency, sensing the rising edge of the timing pulse and setting a bistable circuit, and comparing the signal on the output nodes of the amplifiers channel with the window of permitted values. The bistable circuit is reset upon the occurrence, after the initial setting, of an output signal amplitude within the window of permitted values. Failure of the bistable circuit to reset before the end of the detection phase signals an excessive offset.

Abstract: A method of equalizing a read channel of a mass magnetic memory device comprises attenuating the low frequencies of the spectrum of the analog signal originating from an electromagnetic read transducer without boosting the high frequency harmonic components of the spectrum. The low frequencies of the spectrum of the analog input signal are attenuated with a low pass filter of an order in a range from 6 to 8 and a boost is implemented by introducing two real and opposed zeroes in the transfer function of the filter without altering the group delay.

Abstract: An integrated circuit including two phase-locked loops each with its own oscillator. To prevent locking owing to injection between the two oscillators due to stray currents in the integrated circuit, a noise generator is coupled to the oscillator of one of the loops and a timer is provided for activating the noise generator in a manner such that the noise generated changes the frequency of the oscillator randomly when the other loop is in operation.