PVT-Compensated Phase Mixer for Stable Delay Locked Loops
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Solution Overview
Problem
Conventional phase mixers experience increased jitter due to Process, Voltage, and Temperature (PVT) variations, which affect the phase difference between input signals, leading to instability in delay locked loops and duty cycle correctors.
Innovation Solution
A phase mixer with a phase value adjusting unit that controls the operation to maintain a stable unit phase value by adjusting driving strengths in response to PVT code signals, generated by a ZQ calibration circuit, to compensate for PVT variations, thereby preventing jitter increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional phase mixers are used without PVT compensation, then the device complexity is low, but the jitter increases due to PVT variations affecting phase difference
Solution Approach 1:
The patent applies preliminary action by measuring PVT variations in advance using a replica model that mirrors the actual circuit's PVT characteristics. The measured PVT code is then used to pre-adjust the driving strengths of input signals before phase mixing occurs, preventing jitter accumulation rather than correcting it afterward. This proactive approach maintains phase stability without requiring complex real-time feedback mechanisms.
Solution Approach 2:
The patent introduces a PVT compensation circuit as an intermediary component that includes a replica model, PVT measurement unit, and driving strength adjustment mechanism. This intermediary measures PVT variations and adjusts driving strengths accordingly, acting as a mediator between the input signals and the phase mixing process. The replica model serves as an intermediary representation of the actual circuit's PVT behavior, enabling compensation without directly modifying the main signal path.
2Measurement precision
If the number of driving units is increased to improve phase mixing accuracy, then the phase control precision is improved, but the power consumption increases
Solution Approach 1:
The patent applies dynamics by making the driving strength adjustable rather than fixed. The driving strengths of the first and second input signals are dynamically adjusted based on the measured PVT code, allowing the phase mixer to maintain optimal performance across varying PVT conditions. This dynamic adjustment enables precise phase control without requiring a large number of permanently active driving units, thus reducing power consumption while maintaining accuracy.
Solution Approach 2:
The patent changes the driving strength parameter of the input signals based on PVT variations. By adjusting the driving strength parameter dynamically according to the PVT code, the system maintains accurate phase control without needing to increase the number of driving units. This parameter-based approach allows precise phase mixing with optimized power consumption by activating only the necessary driving units based on current PVT conditions.
Data Source
AI summary
A phase mixer includes a phase mixing unit configured to mix a phase of a first input signal and a phase of a second input signal in response to a phase control signal and output a phase mixed signal whose phase is varied by one or more units of a unit phase value, and a phase value adjusting unit configured to control an operation of the phrase mixing unit so that the unit phase value is adjusted in response to a code signal coding at least one of a process, voltage, or temperature (PVT) variation.