International Business Machines Corporation

Donald E Strayer

Stephen Dale Wyatt

Ilya I Novof

Ram Kelkar

John S Austin

Ilya L Novof

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.

Diffrential charge pump with integrated common mode control

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

Resistorless phase locked loop circuit employing direct current injection

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Owego, NY, United States of America

Donald E Strayer