Phase Interpolator Circuit With Stabilizing Capacitors for Phase Accuracy
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Solution Overview
Problem
Conventional phase interpolators suffer from significant phase errors due to parasitic capacitance connected to source coupled nodes, which varies with connection patterns and input conditions, making it difficult to accurately control the phase of differential output signals.
Innovation Solution
Incorporating stabilizing capacitors between the source coupled nodes and a reference voltage in each differential pair to suppress voltage fluctuations and reduce the influence of parasitic capacitance, allowing for accurate phase control of differential output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase interpolators are used without stabilizing capacitors, then the circuit structure is simple, but significant phase errors occur due to parasitic capacitance
Solution Approach 1:
Stabilizing capacitors are introduced as intermediary elements connected to the source coupled nodes of differential pairs. These capacitors act as mediators that filter out voltage fluctuations caused by parasitic capacitance variations, thereby improving phase accuracy without fundamentally changing the core phase interpolation mechanism
Solution Approach 2:
The invention changes the electrical parameters at the source coupled nodes by adding capacitive elements. This modifies the impedance characteristics and filtering properties of the circuit, enabling better suppression of parasitic effects while maintaining the overall circuit topology
2Reliability
If stabilizing capacitors are added to reduce parasitic capacitance influence, then phase error is reduced, but device complexity increases
Solution Approach 1:
The phase interpolator is segmented into multiple independent differential pairs, each equipped with its own stabilizing capacitor. This segmentation allows each differential pair to independently manage its parasitic capacitance effects, improving overall reliability while distributing the complexity across modular units
Solution Approach 2:
Rather than attempting to eliminate all sources of phase error through complex compensation circuits, the invention applies a simpler partial solution by adding stabilizing capacitors only at the source coupled nodes. This partial action provides sufficient improvement in phase control accuracy without excessive complexity
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
The use of stabilizing capacitors effectively reduces phase errors and enables precise control of the phase of differential output signals, improving the accuracy and reliability of the phase interpolation process.
Implementation Method 1
a first stabilizing capacitor connected between the source coupled node of the first differential pair and a reference voltage, and a second stabilizing capacitor connected between the source coupled node of the second differential pair and the reference voltage
Data Source
AI summary
An exemplary phase interpolator includes a first to a fourth differential pair. Each of the differential pairs includes a first and a second transistor and a stabilizing capacitor connected between a source coupled node and a reference voltage. The phase interpolator also includes a plurality of current sources and a group of switches to switch connections between the source coupled nodes of the differential pairs and the current sources so that (i) a first operating current is supplied to a first selected one of the first and second differential pairs and (ii) a second operating current is supplied to a second selected one of the third and fourth differential pairs. Drains of the first transistors in the differential pairs are commonly connected and drains of the second transistors in the differential pairs are commonly connected to form a first and a second output node so that a differential output signal is output.