Fairchild Semiconductor Corporation

James J McDonald, Ii

Ronald B Hulfachor

Christian Klein

Jim Wunderlich

A voltage controlled oscillator circuit is shown using multiple delay stages with the last stage looped back out of phase to the first stage. Each stage delay is formed by charging one or more capacitors. The circuitry uses active components demonstrating a square law relationship between a control voltage and a resulting current. The current is ultimately used to charge the delay capacitor. The net effect is a linear relationship of the VCO frequency and an input control voltage. The range of the linear relationship is extended by using square law current sources to provide suitable currents that extend the linear range when other active devices are no longer supporting the square law relationship. In addition bipolar device are used to compensate for temperature and batch to batch processing effects of FET devices.

Circuit to linearize gain of a voltage controlled oscillator over wide frequency range

A phase locked loop, PLL, is described with multiple parallel charge pumps that are selectively disabled as phase lock is approached. A lock detection circuit is described that enabled reference currents to be fed to the parallel charge pumps. The error signal from a phase detector is arranged as UP and a DOWN signals that are averaged in the lock detector. When the average error is large, all the reference currents feed the charge pumps that provide a high loop gain to reduce the lock time. As the lock becomes closer selective reference currents are disabled to reduce loop gain so that a smooth transition to lock is made. Selectively switching currents into a low pass filter that usually follows a charge pump in a PLL circuit automatically reduces switching noise by the operation of the low pass filter.

Circuitry to reduce PLL lock acquisition time

A current boost circuit that supplies additional current to a voltage reference power rail. When the voltage reference power rail drops due to an excessive current demand from the load, the drop is sensed and a switch is activated supplying additional current to the voltage reference rail. A gain stage is capacitively coupled to the reference voltage and any drop is transferred through this capacitor to a gain stage that amplifies the drop. The amplified drop is capacitively coupled to a solid state switch that turns on connecting an additional current source to the reference voltage rail. The solid state switch is biased just below its turn on threshold.

Capacitively coupled current boost circuitry for integrated voltage regulator

A phase locked loop circuit is used to provide timing clocks for data bit recovery from a serial data flow. The system locks to a SYNC signal, preferably a lower frequency fifty percent duty cycle square wave with a period equal to the time of a fully framed serial data word. When a start signal transition is detected the system is prevented from trying to lock onto the data signal edge transitions. But, the system provides a signal suitable for clocking in the individual data bits.

PLL for clock recovery with initialization sequence

A buffer circuit with slow output edges is described. Pulsed higher value currents are driven from one shot timing circuits to inject a pulse of current into the control gate of the buffer's output MOSFET to speed up the beginning of the turning on or the turning off of the output MOSFT. When the beginning and turning on and off is reached lower value current sources continue to drive the gate of the output MOSFET. In one embodiment, one shots are triggered from the rising and falling edges of the input signal. The effect of the higher value current pulses is to reduce the circuit delay through the buffer. Also, the pulse width can be designed as temperature sensitive, and supply voltage sensitive so as to maintain the buffer circuit delay as substantially constant as temperature, supply voltage and process variation occur.

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Gorham, ME, United States of America

James J McDonald, Ii