摘要:
A gain compensation technique for a fractional-N phase lock loop includes locking a reference signal with the N divider feedback signal in a phase lock loop including a phase detector, charge pump, loop filter and voltage control oscillator with an N divider in its feedback loop; driving the N divider with a sigma delta modulator including at least one integrator to obtain a predetermined fractional-N feedback signal; and commanding a scaling in phase lock loop gain by a predetermined factor and synchronously inversely scaling by that factor the contents of at least one of the integrators.
摘要:
A charge pump system for a fast locking phase lock loop includes a set n of charge pump units; and a control logic circuit for enabling the set of n charge pump units to produce up and down charge pulses with a nominal charge pump mismatch in a wide bandwidth mode; and in a narrow bandwidth mode enabling at least a subset of the n charge pump units sequentially to produce an average charge pump mismatch in narrow bandwidth mode that matches the nominal charge pump mismatch in the wide bandwidth mode.
摘要:
A fractional-N synthesizer and method of phase synchronizing the output signal with the input reference signal in a fractional-N synthesizer by generating a synchronization pulse at integer multiples of periods of the input reference signal and gating the synchronization pulse to re-initialize the interpolator in the fractional-N synthesizer to synchronize the phase of the output signal with the input reference signal.
摘要:
A fractional-N synthesizer with programmable output phase including a phase locked loop having an output signal whose frequency is a fractional multiple of an input reference signal, the phase locked loop including a frequency divider. A synchronization circuit responsive to the input reference signal for generating synchronization pulses at integer multiples of M periods of the input reference signal. An interpolator is responsive to F and M, where F is the fractional value and M is the modulus, to provide to the frequency divider an output which is a fractional value equal to, on average, the input fraction. A phase adjustment circuit is responsive to the synchronization circuit for varying the phase of the output signal with respect to the input reference signal.
摘要:
A fractional-N synthesizer system including a plurality of fractional-N synthesizers all updated to simultaneously generate an output frequency from the same reference frequency, a phase locked loop having an output signal whose frequency is a fractional multiple of the input reference frequency; the phase locked loop including a frequency divider, an interpolator responsive to an input fraction to provide to the frequency divider an output which has a fractional value equal to on average, the input fraction; and a timeout circuit responsive to the reference frequency for generating an output a predetermined time after updating to initialize the interpolator in each synthesizer to the same start conditions for locking together the phase of the frequency outputs of all of the synthesizers at the updated frequency.
摘要:
A chopped charge pump with matching up and down pulses including a first pair of current sources, a second pair of current sources, and a switching circuit for switching on in a first phase one current source of each pair to provide up current pulses, and the other current source of each pair to provide down current pulses, and switching on in a second phase the other current source of each pair to provide up current pulses, and the one current source of each pair to provide down current pulses to offset error in the current response of the pairs of current sources.
摘要:
A pulse width modulated common mode feedback technique for a differential charge pump includes averaging the output of a differential charge pump to determine the common mode voltage; generating from the pump up and pump down pulses a set of up source pulses and down source pulses and a set of up sink pulses and down sink pulses and adjusting, in response to a difference between a reference voltage and the common mode voltage, the width of at least one of the sets of source and sink pulses to match the reference common mode voltages.
摘要:
A fast lock phase lock loop (PLL) with minimal phase disturbance when switching from wide bandwidth mode to narrow bandwidth mode including a phase frequency detector, a charge pump, a loop filter and a voltage controlled oscillator, and a sequencer circuit for, at a first time, initiating an increase in the charge pump current to increase the loop gain to widen the loop bandwidth and initiating a decrease in the resistance in the loop filter to increase the phase margin of the PLL in the wide bandwidth mode; at a second time, initiating a reduction in the charge pump current to reduce the loop gain and bandwidth, and; at a third time, initiating an increase in the resistance in the loop filter to increase the phase margin of the PLL in the narrow bandwidth mode.