DLL Clock Initialization Using Precharged Control Voltage
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Solution Overview
Problem
During the initial operation of analog DLL circuits, the control voltage level is at ground potential, leading to erroneous operations due to the inability to adjust the phase delay correctly, resulting in unstable clock synchronization.
Innovation Solution
A DLL circuit with a clock selection control unit generating a clock selection signal and an initialization signal, and a delay control unit that uses an initial voltage derived from the external power supply to generate a control voltage, enabling phase adjustment by pulling up or pulling down the voltage level, ensuring the control voltage exceeds ground potential during initialization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the control voltage is at ground potential during initial operation, then the circuit structure is simple, but the phase delay adjustment fails and erroneous operations occur
Solution Approach 1:
The patent applies preliminary action by generating an initial voltage from the external power supply voltage before the DLL circuit begins operation. This initial voltage is stored in a capacitor and used to initialize the control voltage to a level above ground potential, enabling proper phase delay adjustment from the start of operation rather than waiting for the feedback loop to naturally establish correct voltage levels.
Solution Approach 2:
The patent introduces an intermediary initial voltage generation circuit that mediates between the power supply and the delay control unit. This intermediary circuit generates and stores an initial voltage that bridges the gap between ground potential and the required control voltage level, allowing the delay control unit to properly adjust phase delay without direct connection to ground during initialization.
2Ease of operation
If the control voltage level is at ground potential, then the initialization process is simple, but the DLL circuit cannot perform correct phase adjustment
Solution Approach 1:
The initialization process uses preliminary action by pre-generating an initial voltage from the external power supply voltage before phase adjustment begins. This initial voltage is stored in a capacitor and applied to the delay control unit, enabling correct phase adjustment from the start of operation rather than requiring complex initialization sequences or waiting for feedback convergence.
3Device complexity
If no initial voltage is provided, then the circuit design is simpler, but erroneous operations occur during initial operation
Solution Approach 1:
The patent applies preliminary action by generating and storing an initial voltage from the external power supply voltage before the DLL circuit operates. This initial voltage ensures that the control voltage is at the correct level from the start, preventing erroneous operations during initial operation while adding only a simple voltage generation and storage circuit.
Solution Approach 2:
The patent introduces an intermediary initial voltage generation circuit that provides a stable voltage level during initialization, mediating between the power supply and the delay control unit to prevent erroneous operations without significantly complicating the overall circuit design.
Data Source
AI summary
A DLL circuit includes a clock selection control unit configured to generate a clock selection signal on the basis of a phase difference between a reference clock and a feedback clock and, after the clock selection signal is generated, to generate an initialization signal. A delay control unit, when the initialization signal is enabled, transfers an initial voltage to be generated by dividing an external power supply voltage to a delay unit as a control voltage, and controls a delay operation of a delay reference clock to be selected on the basis of the clock selection signal.