Linear Redriver Equalizer With Tunable Zeros for Trace Loss Matching
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Solution Overview
Problem
Existing linear redrivers lack the ability to effectively fine-tune gain profiles and achieve a wide gain range at desired frequencies or frequency bands, leading to suboptimal signal quality in high-speed interfaces.
Innovation Solution
The introduction of an equalizer stage circuit with selectable paths and RC time constant members, allowing for independent control of high-frequency zeros, low-frequency zeros, and high-frequency poles through digital control signals, enabling precise adjustment of gain characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a linear redriver uses a continuous time linear equalizer to boost high-frequency components, then signal integrity is improved, but the ability to fine-tune gain profiles and achieve wide gain range at desired frequencies is limited
Solution Approach 1:
The equalizer stage is segmented into multiple selectable paths (first selectable path for high-frequency zeros, second selectable path for high-frequency poles), each with independent RC time constant members. This segmentation allows independent control of different frequency characteristics, enabling fine-tuned gain profiles across wide frequency ranges while maintaining overall signal integrity.
Solution Approach 2:
The equalizer implements dynamic adjustability through digital control signals that selectively couple different RC time constant members into the signal path. The impedance of each path can be dynamically changed by switching between different R and C values, allowing the gain profile to be adapted in real-time to match various trace loss characteristics and frequency requirements.
2Device complexity
If the equalizer stage uses fixed RC time constant members, then circuit complexity is reduced, but the ability to independently control high-frequency zeros, low-frequency zeros, and high-frequency poles is limited
Solution Approach 1:
Each selectable path contains multiple RC time constant members that can be selectively activated based on digital control signals. The first selectable path controls high-frequency zeros, the second selectable path controls high-frequency poles, and low-frequency zeros are controlled through capacitors coupled to the differential pair. This multi-functional design allows a single equalizer stage to independently control multiple frequency characteristics without requiring separate circuits for each function.
Solution Approach 2:
Digital control signals serve as intermediaries between the control logic and the physical RC time constant members. These control signals selectively couple specific R and C members into the signal path, enabling precise adjustment of gain characteristics without requiring direct manual intervention or complex switching mechanisms. The intermediary control layer simplifies the user interface while maintaining fine-grained control capability.
Data Source
AI summary
An equalizer stage circuit includes a first transistor and a second transistor disposed in a differential configuration. The equalizer stage circuit also includes a first selectable path. The first selectable path includes: a first terminal coupled to an emitter or a source of the first transistor; a second terminal coupled to an emitter or a source of the second transistor; a high-frequency portion comprising a first plurality of high-frequency RC time constant members connected in parallel between the first terminal and the second terminal; a first capacitor coupled to the first terminal; a second capacitor coupled to the second terminal; and a low-frequency portion comprising a second plurality of low-frequency RC time constant members connected between the first capacitor and the second capacitor.