Abstract: An injection-locked oscillator circuit includes a master oscillator, a slave oscillator, and an injection lock control circuit. The slave oscillator is decoupled from the master oscillator (for example, due to an unlock condition). When the slave is free running, its oscillating frequency is adjusted (for example, as a function of a supply voltage). After an amount of time, the slave is to be relocked to the master (for example, due the unlock condition no longer being present). The slave oscillating frequency is made to be slightly lower than the master oscillating frequency. The slave is then only recoupled to the master upon detection of an opposite-phase condition between the master oscillator output signal and the slave oscillator output signal. By only recoupling the slave to the master during opposite-phase conditions, frequency overshoots in the slave oscillating frequency are avoided that may otherwise occur were the recoupling done during in-phase conditions.

Abstract: A circuit for detecting a voltage change is described. The circuit includes a supply insensitive pulse generator that generates a pulse signal. The circuit also includes a time-to-digital converter coupled to the supply insensitive pulse generator. The time-to-digital converter generates a digital signal based on the pulse signal and a voltage. The circuit also includes a controller coupled to the time-to-digital converter that detects a voltage change based on the digital signal.

Abstract: Closed-loop techniques for adjusting the duty cycle of a cyclical signal, e.g., a clock signal, to approach a target value. In an exemplary embodiment, a charge pump is coupled to a charge and sample module, which drives a de-skew circuit in a negative feedback loop. The charge and sample module couples the charge pump to the integration capacitor during two of four successive phases, and also couples the integration capacitor to sampling capacitors during the other two of the four successive phases. The voltages across the sampling capacitors may be used to control the de-skew circuit, which adjusts the duty cycle of a cyclical signal to be adjusted.

Abstract: An injection-locked oscillator circuit includes a master oscillator, a slave oscillator, and an injection lock control circuit. The slave oscillator is decoupled from the master oscillator (for example, due to an unlock condition). When the slave is free running, its oscillating frequency is adjusted (for example, as a function of a supply voltage). After an amount of time, the slave is to be relocked to the master (for example, due the unlock condition no longer being present). The slave oscillating frequency is made to be slightly lower than the master oscillating frequency. The slave is then only recoupled to the master upon detection of an opposite-phase condition between the master oscillator output signal and the slave oscillator output signal. By only recoupling the slave to the master during opposite-phase conditions, frequency overshoots in the slave oscillating frequency are avoided that may otherwise occur were the recoupling done during in-phase conditions.

Abstract: A supply-regulated VCO exhibits reduced or no supply sensitivity peaking. The VCO includes an oscillator whose supply current is regulated to control the oscillating frequency of the oscillator. A VCO input signal controls the supply current so that there is a relationship between the input signal and the oscillator output frequency. Power supply noise that might otherwise affect oscillator operation is shunted from a supply current input lead of the oscillator to ground by a bypass capacitor. In one example, an auxiliary circuit supplies an auxiliary supply current to the oscillator, thereby reducing the amount of supply current a supply regulation control loop circuit must supply. In another example, a supply regulation control loop circuit supplies a control current to a main oscillator, but the bypass capacitor is not coupled to this oscillator but rather is coupled to a slave oscillator that is injection locked to the main oscillator.

Abstract: A latching element latches incoming data into an integrated circuit. The latching element (for example, a latch or flip-flop) can be considered to include a data path portion, a clock path portion, and an ideal latching element. In one embodiment, an open-loop replica of the data path portion is disposed in a clock signal path between a clock input terminal of the integrated circuit and a clock input lead of the latching element. In a second embodiment, an additional replica of the clock path portion is disposed in a data signal path between a data terminal of the integrated circuit and a data input lead of the latching element. The replica circuits help prevent changes in skew between a data path propagation time to the ideal latching element and clock path propagation time to the ideal latching element. Setup times remain substantially constant over PVT (process, supply voltage, temperature).

Abstract: A charge pump includes an UP current mirror and a DN current mirror. The UP current mirror is controlled by an input UP signal and supplies charge onto an output node. The DN current mirror is controlled by an input DN signal and draws charge from the output node. The input UP and DN signals may be received from a phase detector in a Phase-Locked Loop (PLL). To prevent disturbances on bias nodes of the UP and DN current mirrors that otherwise might occur, replica circuits of portions of the UP and DN current mirrors are provided. Each replica circuit is coupled to a bias node of a corresponding current mirror, but is controlled by an input signal of opposite polarity to the input signal that controls the current mirror so that the replica circuit creates disturbances that tend to counteract disturbances created by switching of the current mirror.

Abstract: A supply-regulated VCO exhibits reduced or no supply sensitivity peaking. The VCO includes an oscillator whose supply current is regulated to control the oscillating frequency of the oscillator. A VCO input signal controls the supply current so that there is a relationship between the input signal and the oscillator output frequency. Power supply noise that might otherwise affect oscillator operation is shunted from a supply current input lead of the oscillator to ground by a bypass capacitor. In one example, an auxiliary circuit supplies an auxiliary supply current to the oscillator, thereby reducing the amount of supply current a supply regulation control loop circuit must supply. In another example, a supply regulation control loop circuit supplies a control current to a main oscillator, but the bypass capacitor is not coupled to this oscillator but rather is coupled to a slave oscillator that is injection locked to the main oscillator.

Abstract: An oscillator is disclosed. The oscillator includes a first capacitor. The oscillator also includes a second capacitor. The oscillator further includes a first current source. The oscillator also includes a second current source. The oscillator further includes a comparator that has a first input and a second input. The oscillator also includes a reference node. The oscillator further includes a controller that is configured to selectively couple the first current source to the first capacitor and the second current source to the reference node during a first time period.

Abstract: Techniques for adaptively control of a loop filter sampling interval to mitigate the effects of charge pump output noise in an apparatus including a phase lock loop circuit are provided. In one aspect, the apparatus includes a voltage controlled oscillator (VCO), a phase frequency detector (PFD) providing a phase comparison operation, a loop filter providing a control voltage to lock the VCO to a desired operating frequency, and a charge pump configured to provide an output signal to the loop filter in response to at least one of an UP pulse and a DOWN pulse. The apparatus further includes a sampling switch, coupled between an input of the loop filter, an output of the charge pump, and characterized by a sampling interval.

Abstract: A memory circuit includes a delay module receiving a strobe signal and producing a delayed strobe signal therefrom. The memory circuit also includes a calibration module that initiates recalibration of the delay module when the calibration module discerns that the delayed strobe signal is within a predetermined proximity of an edge of a reference signal. The memory circuit can be included in a memory interface. Furthermore, in some embodiments, a strobe signal can be used as the reference signal.

Abstract: Techniques to effectively handle large voltage-controlled oscillator (VCO) gain are described. The techniques utilize (1) a slow high-gain path to provide an average control current that adjusts the center frequency of a VCO and (2) a fast low-gain path to provide an instantaneous control current that adjusts the VCO frequency during normal operation. In one design, the VCO includes a voltage-to-current converter, a current amplifier, a summer, and a current-controlled oscillator (ICO). The voltage-to-current converter receives a control voltage and generates a first current and a second current. The current amplifier amplifies and filters the first current and generates a third current. The summer sums the second current and the third current and generates a control current. The ICO receives the control current and generates an oscillator signal having a frequency determined by the control current.

Abstract: A programmable delay circuit capable of providing a delay with integer and fractional time resolution is described. In one exemplary design, an apparatus includes first and second delay circuits. The first delay circuit provides a first delay of an integer number of time units. The second delay circuit couples to the first delay circuit and provides a second delay of a fraction of one time unit. The first delay circuit may include multiple unit delay cells coupled in series. Each unit delay cell may provide a delay of one time unit when enabled. The second delay circuit may have first and second paths. The first path may provide a shorter delay when selected, and the second path may provide a longer delay when selected. The second path may be coupled to at least one dummy logic gate that provides extra loading to obtain the longer delay for the second path.

Abstract: A charge pump includes an UP current mirror and a DN current mirror. The UP current mirror is controlled by an input UP signal and supplies charge onto an output node. The DN current mirror is controlled by an input DN signal and draws charge from the output node. The input UP and DN signals may be received from a phase detector in a Phase-Locked Loop (PLL). To prevent disturbances on bias nodes of the UP and DN current mirrors that otherwise might occur, replica circuits of portions of the UP and DN current mirrors are provided. Each replica circuit is coupled to a bias node of a corresponding current mirror, but is controlled by an input signal of opposite polarity to the input signal that controls the current mirror so that the replica circuit creates disturbances that tend to counteract disturbances created by switching of the current mirror.

Abstract: A memory circuit includes a delay module receiving a strobe signal and producing a delayed strobe signal therefrom. The memory circuit also includes a calibration module that initiates recalibration of the delay module when the calibration module discerns that the delayed strobe signal is within a predetermined proximity of an edge of a reference signal. The memory circuit can be included in a memory interface. Furthermore, in some embodiments, a strobe signal can be used as the reference signal.

Abstract: A supply-regulated Phase-locked loop (PLL) is provided. The PLL comprises a supply-regulating loop, a voltage-controlled oscillator (VCO), and a programmable decoupling capacitor array for the VCO. The capacitance of the VCO decoupling capacitor array is adjustable to be equal to N times CUNIT, where N is the current value of a multiplication factor of a divide-by-N circuit and CUNIT is a unit capacitance characterized for a processing technology chosen for fabricating the decoupling capacitor array. When the PLL switches from one frequency band to another, a higher-order pole introduced by the VCO decoupling capacitor tracks the PLL reference frequency, thus improving the PLL operational stability.

Abstract: Delay circuits capable of providing delays closely matching propagation delays of synchronous circuits are described. In one design, an apparatus includes a synchronous circuit and a delay circuit. The synchronous circuit includes a forward path from a data input to a data output. The synchronous circuit receives input data and provides output data with a propagation delay. The delay circuit receives an input signal and provides a delayed input signal having a delay matching the propagation delay of the synchronous circuit. The delay circuit includes at least two logic gates in the forward path of the synchronous circuit. The synchronous and delay circuits may be implemented based on the same or similar circuit architecture. The delay circuit may be based on a replica of the synchronous circuit, with the replica having feedback loops broken and clock input coupled to appropriate logic value to always enable the delay circuit.

Abstract: Techniques for adaptively control of a loop filter sampling interval to mitigate the effects of charge pump leakage current in an apparatus including a phase lock loop circuit are provided. In one aspect, the apparatus includes a voltage controlled oscillator (VCO), a phase frequency detector (PFD) providing a phase comparison operation, a loop filter providing a control voltage to lock the VCO to a desired operating frequency, and a charge pump configured to provide an output signal to the loop filter in response to at least one of an UP pulse and a DOWN pulse. The apparatus further includes a sampling switch, coupled between an input of the loop filter, an output of the charge pump, and characterized by a sampling interval.

Abstract: Closed-loop techniques for adjusting the duty cycle of a cyclical signal, e.g., a clock signal, to approach a target value. In an exemplary embodiment, a charge pump is coupled to a charge and sample module, which drives a de-skew circuit in a negative feedback loop. The charge and sample module couples the charge pump to the integration capacitor during two of four successive phases, and also couples the integration capacitor to sampling capacitors during the other two of the four successive phases. The voltages across the sampling capacitors may be used to control the de-skew circuit, which adjusts the duty cycle of a cyclical signal to be adjusted.

Abstract: A latching element latches incoming data into an integrated circuit. The latching element (for example, a latch or flip-flop) can be considered to include a data path portion, a clock path portion, and an ideal latching element. In one embodiment, an open-loop replica of the data path portion is disposed in a clock signal path between a clock input terminal of the integrated circuit and a clock input lead of the latching element. In a second embodiment, an additional replica of the clock path portion is disposed in a data signal path between a data terminal of the integrated circuit and a data input lead of the latching element. The replica circuits help prevent changes in skew between a data path propagation time to the ideal latching element and clock path propagation time to the ideal latching element. Setup times remain substantially constant over PVT (process, supply voltage, temperature).