PLL Bandwidth Control via Dynamic PVT Compensation
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Solution Overview
Problem
Phase Locked Loops (PLLs) face challenges in maintaining constant bandwidth under Process, Voltage, and Temperature (PVT) variations, leading to fluctuations in lock time and jitter, which existing technologies fail to effectively address.
Innovation Solution
The solution involves adjusting parameters such as the current of the PLL, capacitance of the loop filter, and gain of the voltage-controlled oscillator to maintain a constant bandwidth, using a controller that generates a control signal based on PVT variations to adjust these parameters, ensuring consistent lock time and jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the PLL bandwidth is fixed, then the circuit design is simple, but the lock time and jitter vary under PVT variations
Solution Approach 1:
The patent implements dynamic bandwidth adjustment by making the PLL bandwidth variable rather than fixed. A bandwidth control circuit dynamically adjusts the loop filter parameters (resistors and capacitors) based on detected PVT variations, allowing the system to adapt to changing conditions and maintain stable lock time and jitter performance across different operating scenarios.
Solution Approach 2:
The patent changes the electrical parameters of the loop filter components (resistors and capacitors) to adjust the PLL bandwidth. By varying the resistance and capacitance values in response to PVT conditions, the system maintains optimal lock time and jitter characteristics without requiring a completely redesign of the PLL architecture.
2Loss of time
If the PLL bandwidth is increased, then the lock time is reduced, but the jitter increases
Solution Approach 1:
The system dynamically adjusts the PLL bandwidth based on real-time PVT detection. When temperature, voltage, or process variations occur, the bandwidth control circuit modifies the loop filter parameters to optimize the balance between lock time and jitter, preventing the system from being locked into a suboptimal fixed bandwidth configuration.
Solution Approach 2:
The patent employs a feedback mechanism where PVT variations are detected and used to control the bandwidth adjustment. The system continuously monitors operating conditions and adjusts the PLL bandwidth accordingly, creating a closed-loop control system that balances lock time and jitter performance based on actual system state rather than static pre-configured values.
3Reliability
If the PLL bandwidth is decreased, then the jitter is reduced, but the lock time increases
Solution Approach 1:
The system transitions from a static bandwidth configuration to a dynamic one where the bandwidth is continuously adjusted based on PVT conditions. This allows the system to optimize for low jitter when conditions permit longer lock times, while still being capable of faster locking when conditions require it, thereby resolving the trade-off between these two parameters.
4Reliability
If PVT variations are compensated, then the lock time and jitter stability is improved, but the device complexity increases
Solution Approach 1:
The patent introduces a bandwidth control circuit as an intermediary component that mediates between the PVT variations and the PLL core. This control circuit contains the complexity of the compensation mechanism, using variable resistors and capacitors in the loop filter to adjust bandwidth without requiring complex digital processing or multiple separate compensation circuits for each PVT parameter.
Solution Approach 2:
The system compensates for PVT variations by changing the electrical parameters of the loop filter components. By adjusting resistance and capacitance values through simple variable components rather than complex digital control mechanisms, the patent achieves bandwidth stability with minimal increase in device complexity.
Data Source
AI summary
A clock generator and a method to control an associated system are described. The clock generator (e.g., a PLL) can include a charge pump that can generate a current, and a controller coupled to the charge pump. The controller can determine a characteristic impacting operation of the clock generator and control the charge pump to adjust the current based on the determined characteristic to adjust a bandwidth of the clock generator. The clock generator and method can include adjusting the bandwidth to compensate for variations (e.g. PVT variations) that impact the operation of the clock generator to maintain constant or substantially constant bandwidth independent of such variations.