Abstract: The phase-looked loop having spread spectrum clock generator of this invention comprises a phase-locked loop and a spread spectrum clock generator. The input signal of the phase-locked loop comes from a reference clock source. The output of the phase-locked loop is used as the standard clock signal and is also supplied to the spread spectrum clock generator, as its input. The spread spectrum clock generator comprises a clock frequency divider, a multiplexer and a counter. The clock frequency divider generates, based on the output of the phase-locked loop, at least tow of a divided-by-M frequency, a divided-by-M+1 frequency and a divided-by-M?1 frequency, which are supplied to the multiplexer. The phase selection of the multiplexer is supplied by the counter, which input is supplied by the output of the multiplexer. The output signal of the multiplexer is supplied to the phase-locked loop, as its feedback clock frequency.

Abstract: A phase-locked loop (PLL) circuit includes a voltage-controlled oscillator (VCO) having a first input to receive a control voltage, one or more second inputs to receive one or more tuning range control signals, and an output to provide an oscillation output signal, a phase detector having inputs to receive the oscillation output signal and a reference signal, a charge pump having an input coupled to the output of the phase detector and having an output to generate the control voltage, a loop filter having an input to receive the control voltage and having a control terminal, and a controller having inputs to receive the control voltage, a high reference voltage, a low reference voltage, and one or more mode signals, and having a first output connected to the control terminal of the loop filter and second outputs to generate the tuning range signals.

Abstract: A high-speed I/O driver includes circuitry that is configurable to meet single-ended and differential I/O signal standards. For one embodiment, the driver includes four input circuits that can be configured to implement two CMOS inverters to process single-ended signals or configured to implement a differential circuit to process differential signals.

Abstract: An input buffer circuit includes a first differential circuit, a second differential circuit, a pull-up circuit, and a pull-down circuit. An input voltage and a reference voltage are provided to the first and second differential circuits. The first differential circuit detects rising edges of the input voltage and causes the pull-up circuit to quickly drive an output voltage to logic high. The second differential circuit detects falling edges of the input voltage and causes the pull-down circuit to quickly drive the output voltage to logic low.

Abstract: A termination resistor circuit includes a first and second passive resistive elements coupled in series between a common mode voltage and a signal node, and a plurality of active resistive elements coupled in parallel with the first passive resistive element. The active resistive elements may be selectively enabled by corresponding control signals to provide various numbers of parallel resistances across the first passive resistive element, thereby tuning the termination resistor circuit to a desired resistance value.