Abstract:
A circuit and method for referenceless CDR with improved efficiency and jitter tolerance by using an additional loop for frequency detection. Such an improved circuit includes a frequency detector for identifying whether an initial recovered clock signal is faster or slower than the actual bit rate of the received data stream. The frequency detector provides a jitter tolerance of +/−0.5 UI and uses significantly fewer components that other conventional frequency detectors. Having fewer components, significantly less power is also consumed. In an embodiment, the FD uses only four flip-flops, two AND gates, and one delay circuit. Having fewer components also uses less die space in integrated circuits. Having high jitter tolerance and fewer components is an improvement over conventional referenceless CDR circuits.
Abstract:
Disclosed is a system and method for providing a critical path replica system in a circuit. A critical path replica system is created by determining a critical path in a circuit, generating a critical path replica circuit, generating a circuit blueprint, and creating the blueprinted circuit. The circuit comprises a functional logic module having functional logic elements and replica logic modules having logic elements. Each logic element is configured to replicate one or more of the functional logic elements and process a test signal. A replica error detection module analyzes the processed signal to determine whether a timing violation has occurred. In some embodiments, the replica logic module further comprises one or more load modules. A replica controller may modify operation of the circuit based on reported errors. A replica mode select module sets the replica logic module to an aging test mode or a timing sensor mode.
Abstract:
A variable frequency clock generator. In aspects, a clock generator includes a droop detector circuit configured to monitor a voltage supply to an integrated circuit. If the supply voltage falls below a specific threshold, a droop voltage flag may be set such that a frequency-locked loop is triggered into a droop voltage mode for handling the voltage droop at the supply voltage. In response, a current control signal that is input to an oscillator that generates a system clock signal is reduced by sinking current away from the current control signal to the oscillator. This results in an immediate reduction on the system clock frequency. Such a state remains until the voltage droop has dissipated when the current path is removed for sinking some of the current.
Abstract:
A temperature sensing circuit a switched capacitor circuit selectively samples ΔVbe and Vbe voltages and provides the sampled voltages to inputs of an integrator. A quantization circuit quantizes outputs of the integrator to produce a bitstream. When a most recent bit of the bitstream is a logic zero, operation includes sampling and integration of ΔVbe a first given number of times to produce a voltage proportional to absolute temperature. When the most recent bit of the bitstream is a logic one, operation includes cause sampling and integration of Vbe a second given number of times to produce a voltage complementary to absolute temperature. A low pass filter and decimator filters and decimates the bitstream produced by the quantization circuit to produce a signal indicative of a temperature of a chip into which the temperature sensing circuit is placed.
Abstract:
A phase lock loop (PLL) includes an input comparison circuit configured to compare a reference signal to a divided feedback signal and generate at least one charge pump control signal based thereupon. A charge pump generates a charge pump output signal in response to the at least one charge pump control signal. A loop filter is coupled to receive and filter the charge pump output signal to produce an oscillator control signal. An oscillator generates an output signal in response to the oscillator control signal, with the output signal divided by a divisor using divider circuitry to produce the divided feedback signal. Divisor generation circuitry is configured to change the divisor over time so that a frequency of the divided feedback signal changes from a first frequency to a second frequency over time.
Abstract:
A PLL includes an input comparison circuit comparing a reference signal to a divided feedback signal to thereby control a charge pump that generates a charge pump output signal. A filter receives the charge pump output signal when a switch is closed, and produces an oscillator control signal causing an oscillator to generate an output signal. Divider circuitry divides the output signal by a divisor to produce the divided feedback signal. Divisor generation circuitry changes the divisor over time so the output signal ramps from a start frequency to an end frequency. Modification circuitry stores a first oscillator control signal equal to the value of the oscillator control signal when the frequency of the output signal is the start ramp frequency. When the frequency of the output signal reaches the end ramp frequency, the switch is opened, and the stored first oscillator control signal is applied to the loop filter.
Abstract:
A phase locked loop (PLL) circuit disclosed herein includes a phase detector receiving a reference frequency signal and a feedback frequency signal and configured to output a digital signal indicative of a phase difference between the reference frequency signal and the feedback frequency signal. A digital loop filter filters the digital signal. A digital to analog converter converts the filtered digital signal to a control signal. An oscillator generates a PLL clock signal based on the control signal. A sigma-delta modulator modulates a divider signal as a function of a frequency control word. A divider divides the PLL clock signal based on the divider signal, and generates a noisy feedback frequency signal based thereupon. A noise filtering block removes quantization noise from the noisy feedback frequency signal to thereby generate the feedback frequency signal.
Abstract:
A circuit includes an oscillator circuit to receive a bias current and generate an oscillating signal at an output node. A current differencing circuit subtracts a current at the output node from a reference current to generate a first current. In addition, a current mirroring circuit mirrors the first current to generate the bias current. An inverter stage is coupled to the output node, and includes an input branch configured to receive the oscillating signal and generate first and second control signals based upon the oscillating signal. At least one amplifying branch receives the first and second control signals and amplifies the first and second control signals. An output branch receives the amplified first and second control signals and generates an amplified version of the oscillating signal based upon the amplified first and second control signals.
Abstract:
A method and apparatus are provided. The apparatus includes a plurality of devices forming a positive feedback loop for driving a regulated output voltage towards a reference voltage. Device ratios of at least two of the plurality of devices are set such that the positive feedback loop is stable.
Abstract:
Adaptive scaling digital techniques attempt to place the system close to the timing failure so as to maximize energy efficiency. Rapid recovery from potential failures is usually by slowing the system clock and/or providing razor solutions (instruction replay.) These techniques compromise the throughput. This application presents a technique to provide local in-situ fault resilience based on dynamic slack borrowing. This technique is non-intrusive (needs no architecture modification) and has minimal impact on throughput.