Xilinx, Inc.

Jack Siu Cheung Lo

Shi-dong Zhou

Shankar Lakkapragada

Andy T Nguyen

An integrated clock doubler and polarity control circuit are described. The circuit provides high speed response between an input signal and an output signal, achieving clock doubling by passing the input signal through a delay circuit and using the output of the delay circuit to select between two paths for inverting or not inverting the input signal to produce the output signal. In one embodiment, the inverting path is a CMOS inverter with input terminal receiving the input signal, output terminal providing the output signal, and power terminals controlled by the delay circuit.

Pulse generator with polarity control

A clock divider circuit that adds little additional delay on the clock path. Each rising and falling edge of an input clock signal triggers a pulse from a pulse generator circuit. These pulses are passed to a control circuit. True and complement versions of the input clock signal are provided to a multiplexer circuit. Under the direction of the control circuit, the multiplexer circuit passes selected rising edges of the true clock signal, and selected falling edges of the complement clock signal, to an output clock terminal of the clock divider circuit. When neither the true nor the complement clock signal is passed by the multiplexer, a keeper circuit retains the value already present at the output clock terminal.

Clock divider circuit with duty cycle correction and minimal additional delay

Frequency doubler with polarity control

A power-on reset (POR) circuit that delays de-assertion a POR control signal in an IC device such that, when unstable power levels are detected, the POR control signal is maintained in an asserted condition until the IC device is fully reset. During a start-up phase of the IC device operation, the POR control circuit maintains the POR control signal in the asserted condition for a delay period whose length is determined, in part, by the amount of noise in the applied power. After the internal voltage of the IC device achieves a steady state for a suitable period of time, the POR control circuit de-asserts the POR control signal, thereby initiating configuration of the IC device. Subsequently, if a low power condition is detected, the POR control circuit asserts the POR control signal, and maintains the POR control signal in the asserted condition for a pre-defined delay period after the low-power event is detected, thereby allowing the IC device to fully reset.

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San Jose, CA, United States of America

Jack Siu Cheung Lo