DLL Clock Skew Control Using Transmission Line Delay Measurement
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Solution Overview
Problem
In clock distribution networks, it is challenging to maintain synchronized phase of clock signals across multiple devices due to varying signal path lengths, requiring time-consuming calibration and frequent recalibration, especially when path lengths are unknown.
Innovation Solution
A system comprising a clock signal generator, delay-lock loops (DLLs), and a delay controller that determines transmission line lengths using roundtrip time and amplitude of test signals, adding delays to ensure clock signals arrive at devices with a desired phase, while ignoring false reflections using estimated values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual skew compensation is used with compensation circuits located near devices, then phase synchronization can be achieved, but calibration becomes time-consuming and difficult
Solution Approach 1:
The system performs self-calibration by automatically measuring transmission line characteristics and computing delay adjustments without manual intervention. The delay controller autonomously determines path lengths and configures DLL delays to achieve phase synchronization, eliminating the need for manual skew compensation procedures
Solution Approach 2:
The system performs preliminary measurement of transmission line characteristics during initialization or setup phase. By pre-determining path lengths and computing required delay adjustments before actual operation, the system avoids time-consuming calibration during device deployment or reconfiguration
2Ease of manufacture
If signal paths have unknown lengths, then system setup is simpler, but phase control becomes difficult
Solution Approach 1:
The system replaces physical measurement methods (such as time-domain reflectometry or physical path length measurement) with electrical characterization through signal transmission. By measuring transmission characteristics electrically, the system maintains ease of setup while achieving precise phase control through computed delay adjustments
Solution Approach 2:
The delay controller acts as an intermediary that translates unknown physical path lengths into precise delay adjustments. By introducing controllable delay elements in the signal path and adjusting them based on measured characteristics, the system achieves phase control without requiring prior knowledge of transmission line lengths
3Reliability
If delay adjustments are made to compensate for path length differences, then phase synchronization is improved, but device complexity increases
Solution Approach 1:
The delay-lock loops serve multiple functions: they provide clock signal distribution, enable phase synchronization, and perform automatic delay adjustment based on measured path characteristics. By consolidating these functions into a single integrated mechanism, the system achieves phase synchronization without proportionally increasing device complexity
Solution Approach 2:
The system merges the delay adjustment functionality with the existing clock distribution infrastructure by integrating delay controllers and DLLs into the signal path. This consolidation allows phase synchronization to be achieved using components that also perform clock generation and distribution, rather than adding separate dedicated delay compensation systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach simplifies the calibration process, ensures consistent phase arrival of clock signals across devices, and allows for dynamic adjustment of delays to maintain synchronization, reducing the need for frequent recalibration.
Implementation Method 1
the delay controller computes the length of each transmission line based at least in part on a roundtrip time and amplitude for a reflection of a test signal transmitted over each transmission line
Implementation Method 2
the delay controller computes the length of each transmission line based at least in part on a roundtrip time
Data Source
AI summary
Systems and methods for transmitting a signal having a desired phase at the device are disclosed. The systems and methods further include determining a signal path length to a device over a transmission line and adding a delay to a signal to be transmitted over the transmission line. The determination is made in response to determining the path length to the device.