Digital Phase Mixer Break-Before-Make Circuit for Wide Frequency Range
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Solution Overview
Problem
Conventional phase locked loops (PLLs) and delay locked loops (DLLs) with digital phase mixers face issues of 'fighting' conditions due to timing gaps between early and late input signals, leading to short circuit currents and reduced reliability, power dissipation, and limited frequency range.
Innovation Solution
The development of a one-bit digital phase mixer with distributed break-before-make drivers, feedback loops, and early turn-off, which uses separate pull-up and pull-down paths with controlled slew rates and duty cycles to prevent 'fighting' conditions, and a six-weight phase mixer with break-before-make drivers and feedback loops to enhance frequency performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional digital phase mixers are used with timing gaps between early and late input signals, then phase mixing function is achieved, but fighting conditions occur leading to short circuit currents and reduced reliability
Solution Approach 1:
The patent applies preliminary action by using break-before-make drivers that preemptively disconnect the late input signal path before connecting the early input signal path. This timing control prevents the fighting condition where both paths are simultaneously active, thereby eliminating short circuit currents and improving reliability before the harmful condition can occur.
Solution Approach 2:
The patent implements feedback through control logic that monitors the timing relationships between early and late input signals and dynamically adjusts the driver activation sequences. This feedback mechanism ensures that drivers are switched in a controlled manner that prevents fighting conditions while maintaining proper phase mixing operation across varying frequency ranges.
2Speed
If conventional phase mixers operate at high frequencies, then frequency range is extended, but fighting conditions increase leading to power dissipation and reduced reliability
Solution Approach 1:
The break-before-make driver architecture performs preliminary disconnection of one signal path before activating the other, preventing simultaneous conduction of early and late signals. This eliminates fighting conditions that would otherwise cause excessive power dissipation at high frequencies, enabling extended frequency range operation without proportional increase in power consumption.
3Reliability
If distributed break-before-make drivers with feedback loops are implemented, then fighting conditions are reduced and reliability improves, but device complexity increases
Solution Approach 1:
The patent segments the phase mixer into multiple independent driver units, each equipped with break-before-make control logic and feedback loops. This segmentation allows each driver to operate autonomously with simplified control, reducing the overall complexity burden while collectively achieving improved reliability through elimination of fighting conditions across all driver stages.
Data Source
AI summary
The present disclosure is directed to a unit phase mixer in combination with an input buffer. The unit phase mixer has a pull-up path for pulling an output terminal up to a first voltage. The pull-up path has a first transistor responsive to a first enable signal and a series connected second transistor responsive to a first clock signal. The unit phase mixer has a pull-down path for pulling the output terminal down to a second voltage. The pull-down path has a third transistor responsive to a second clock signal and a series connected fourth transistor responsive to a second enable signal. The input buffer skews the first and second clock signals by different amounts to enable a break-before-make method of operation so that the first voltage is not connected to the second voltage. The unit phase mixer can be used as a building block in more complex mixers which may include the ability to weight the input clocks as well as providing feed-forward paths for certain of the signals. Because of the rules governing abstract, this abstract should not be used to construe the claims.