Nonlinear Charge Pump Switching for Fast PLL Relock
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Solution Overview
Problem
Phase lock loops (PLLs) face challenges in quickly reacquiring frequency lock after disruptions, such as single-event transients, due to limitations in charge pump power, leading to a trade-off between reacquisition time and jitter, which hinders their effectiveness in communication systems and radiation hardening applications.
Innovation Solution
A non-linear charge pump system with an auxiliary charge pump that dynamically adjusts the loop bandwidth by using a positive switch, current source, negative switch, windowing comparator, and activation circuit to supplement power, allowing for faster reacquisition of frequency lock while minimizing jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If power is increased to the charge pump to reduce reacquisition time, then reacquisition time is improved, but jitter increases
Solution Approach 1:
The patent implements dynamic bandwidth adjustment by switching between a first charge pump with lower current and a second charge pump with higher current based on the operational state of the PLL. During frequency acquisition, the higher current pump is activated to reduce reacquisition time. Once lock is achieved, the system switches to the lower current pump to minimize jitter, thereby dynamically optimizing performance based on real-time needs
Solution Approach 2:
The invention changes the current parameter of the charge pump dynamically by selecting between two different charge pumps with different current characteristics. The system monitors the lock state and adjusts the pump current accordingly - using high current during acquisition phase and low current during steady-state operation, thus resolving the contradiction between fast reacquisition and low jitter
2Productivity
If a single charge pump is used, then device complexity is reduced, but the ability to quickly reacquire frequency lock is limited
Solution Approach 1:
The patent divides the charge pump function into two separate charge pumps: a first charge pump for normal operation and a second charge pump for fast reacquisition. This segmentation allows each pump to be optimized for its specific function - the second pump can be designed with higher current capability for rapid locking without compromising the low jitter performance of the first pump during steady-state operation
Solution Approach 2:
The system implements multi-functionality by having two charge pumps that can serve different purposes - the first charge pump handles normal frequency locking with low jitter, while the second charge pump provides fast reacquisition capability when needed. The control logic selectively activates the appropriate pump based on system state, making the overall system capable of both low-jitter operation and rapid recovery
Data Source
AI summary
A non-linear charge pump for phased lock loops. Furthermore, an auxiliary charge pump apparatus, comprising a positive switch electrically connected to a current source configured to supplement power to a charge pump, a negative switch electrically connected to a current sink configured to discharge power from the charge pump, a windowing comparator, further comprising an input signal received from a phase-locked loop, a first comparator configured to compare the input signal against a high voltage threshold, a second comparator configured to compare the input signal against a low voltage threshold, an AND logic gate configured to provide a window signal and an activation circuit electrically connected to the positive switch and negative switch. Additionally, a non-linear charge pump system and method for reacquiring frequency lock of a phase lock loop.