Replica Charge Pump Feedback for Timing Mismatch Cancellation
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Solution Overview
Problem
Charge pumps in phase comparison applications suffer from transient mismatches due to timing delays, leading to non-zero average current errors even when signals have no phase difference, which worsens at higher frequencies, causing noise and offset control loop errors.
Innovation Solution
Coupling a primary charge pump with a replica charge pump and using a difference amplifier to measure and cancel error currents, ensuring equal but opposite currents are produced to maintain constant output voltage, and employing feedback to match transient outputs and steady-state voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If charge pump frequency is increased to improve productivity, then output current response speed is improved, but transient timing mismatches worsen causing non-zero average current errors
Solution Approach 1:
The patent implements a feedback mechanism where the charge pump output is fed back to dynamically adjust the timing of control signals. This feedback loop detects transient mismatches and compensates for them in real-time, allowing the system to maintain high frequency operation while correcting timing errors that would otherwise cause non-zero average current. The feedback enables the system to adapt to transient conditions without sacrificing either speed or accuracy.
Solution Approach 2:
The patent dynamically changes the timing parameters of control signals based on detected errors. By adjusting the enable/disable timing of charge pump currents in response to measured deviations, the system optimizes performance at different frequencies. This parameter adjustment allows the charge pump to maintain accuracy across a range of operating frequencies rather than being limited to a single optimal point.
2Loss of time
If charge pump operating frequency is increased to reduce loop response time, then response speed is improved, but transient errors increase causing more noise and offset
Solution Approach 1:
The feedback mechanism continuously monitors the charge pump output and detects transient timing mismatches. By feeding this information back to adjust control signal timing, the system can operate at high frequencies for fast response while simultaneously correcting the transient errors that generate noise and offset. The feedback ensures that harmful transient effects are compensated in real-time.
Solution Approach 2:
The patent converts the harmful effect of transient timing mismatches into useful information for correction. By measuring the transient errors that naturally occur at high frequencies, the system uses this error information to adjust timing and eliminate the very errors it detects. This transforms the harmful transient effects into a basis for self-correction, allowing high-speed operation without the usual penalty of increased noise and offset.
Data Source
AI summary
In an embodiment, a primary charge pump and replica charge pump may be coupled to matching control mechanisms and loads. In an embodiment, the replica charge pump may produce an error current originating from charge pump timing mismatches in a steady locked loop state. The error current produced by the replica charge pump may be measured by a difference amplifier to adjust at least one current source to compensate for the error current originating from the timing mismatches. To adjust the current sources, the amplifier may cause the current source to produce an equal but opposite current to cancel the effects of the error current, resulting in a constant output voltage.