US 4,902,986 A · Phased locked loop to provide precise frequency and phase tracking of two signals

Abstract

A device and method are presented which allows the precise generation of signals within an integrated circuit that are calibrated to an external reference signal. The device consists of a ring oscillator which generates a calibration signal oscillating at a first frequency and a power source that supplies a compensated power signal to the ring oscillator. The first frequency is variable based on the voltage of the compensated power signal. A phase detector is used to detect the relative phase of the calibration signal and the external reference signal. The compensated power signal is also used for critical data paths within the integrated circuit where precise timing is required. In a tester, a plurality of signals may be extracted from the ring oscillator using a series of taps. These signals will oscillate at the same frequency as the calibration signal, but will be phase shifted. The signals may be combined with multiplexors to form a test signal which is applied to a device under test (DUT). Further, in order to make transparent propagation delay, delayed calibration signals may be generated.

Claims14

Dependent claims

A device for use within an integrated circuit and which utilizes an external reference oscillating signal to calibrate signals within the integrated circuit, the device comprising:

a ring oscillator for generating a calibration signal oscillating at a first frequency which is to be matched to the frequency of oscillation of the external reference oscillating signal;
a power source for supplying a compensated power signal to the ring oscillator, the frequency of oscillation of said calibration signal increasing when the voltage of said compensated power signal is increased, and the frequency of oscillation of said calibration signal decreasing when the voltage of said compensated power signal is decreased, the voltage of said compensated power signal being responsive to a control signal;
and
phase detector means, coupled to the power source, for receiving as input said calibration signal and said reference oscillating signal and for generating said control signal, the phase detector means varying said control signal so that said first frequency matches the frequency of oscillation of the external reference oscillating signal;
wherein said compensated power signal is used in other portions of the integrated circuit which are critical data paths.

2 more elements

An integrated circuit for use with a tester of a first device and which integrated circuit utilizes an external reference oscillating signal to calibrate signals generated within the integrated circuit for transfer to the first device, the integrated circuit comprising:

a ring oscillator for generating a calibration signal oscillating at a first frequency which is to be matched to the frequency of oscillation of said external reference oscillating signal;
a power source that supplies a compensated power signal to the ring oscillator, the frequency of oscillation of said calibration signal increases when the voltage of said compensated power signal is increased, and the frequency of oscillation of said calibration signal decreasing when the voltage of said compensated power signal is decreased, the voltage of said compensated power signal being responsive to a control signal;
phase detector means, coupled to the power source, for receiving as input said calibration signal and said reference oscillating signal and for generating said control signal, the phase detector means varying said control signal so that the first frequency matches the frequency of oscillation of said external reference oscillating signal;
and
a plurality of taps, each tap coupled to the ring oscillator at a different location of the ring oscillator each tapping the ring oscillator so as to generate a first plurality of signals which are phase shifted from said calibration signal.

2 more elements

The method for generating calibrated signals within an integrated circuit for application within a tester which tests a first device, the method comprising the following steps:

a. generating a calibration oscillating signal using a first plurality of inverters forming a ring oscillator;
and
b. varying the voltage of a power signal supplying power to said first plurality of inverters in order to match the frequency of oscillation of said calibration oscillating signal to the frequency of oscillation of an external reference oscillating signal;
c. tapping an output of each of said first plurality of inverters to produce a first plurality of signals;
and
d. multiplexing said first plurality of signals with a plurality of multiplexors to produce a test signal for application to said first device.

3 more elements

Dependencies are inferred from the claim text.

Phased locked loop to provide precise frequency and phase tracking of two signals

Life of this patent

Phased locked loop to provide precise frequency and phase tracking of two signals

Life of this patent

Abstract

Claims14