Active Echo On-Die Repeater Circuit for Long RC Interconnects
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Solution Overview
Problem
As integrated circuits (ICs) operate at higher speeds with decreasing voltages, long signal interconnects on ICs face issues with resistance and capacitance, leading to signal transition delays and potential circuit damage due to crowbar currents, which existing repeater circuits may not adequately address.
Innovation Solution
A repeater circuit design featuring a static-dynamic-dynamic configuration with a keeper circuit and split feedback paths, utilizing dynamic and static transistors to drive signals effectively across longer interconnects, reducing RC sensitivity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If repeater circuits are placed along long signal interconnects to overcome resistance and capacitance effects, then signal transition speed at the receiver is improved, but device complexity increases
Solution Approach 1:
The repeater circuit is segmented into distinct functional blocks: an activation stage that detects input transitions, an output stage that drives the output node, and a feedback path that provides delayed feedback. This segmentation allows each stage to be optimized independently for its specific function while working together to achieve fast signal transition.
Solution Approach 2:
The circuit employs dynamic transistor operation where transistors are turned on and off based on input signal transitions rather than remaining statically on. The activation stage dynamically activates the output stage only when needed, and the feedback path dynamically controls the timing of transistor deactivation, enabling fast transitions while managing complexity through controlled dynamic behavior.
2Use of energy by moving object
If dynamic transistors are used in the repeater circuit to reduce power consumption, then energy efficiency is improved, but reliability may worsen due to potential circuit damage from crowbar currents
Solution Approach 1:
The feedback path delays the output signal and uses it to control the deactivation of transistors in the output stage. This feedback mechanism ensures that transistors remain active long enough to complete the signal transition fully before turning off, preventing premature shutdown that could cause crowbar currents. The feedback-controlled timing maintains reliability while allowing dynamic power savings.
Solution Approach 2:
The activation stage detects input transitions in advance and proactively activates the output stage before the full signal transition completes. This preliminary activation ensures that the output stage is ready to drive the interconnect immediately when needed, reducing power consumption by avoiding repeated activation cycles while maintaining reliability through proper timing control.
3Loss of time
If the output stage is activated early to overcome interconnect RC effects, then signal transition timing is improved, but setup and hold time for the receiver may be insufficient
Solution Approach 1:
The feedback path takes the output signal, delays it through the feedback network, and uses this delayed signal to control transistor deactivation. This ensures that the output stage remains active for the precise duration needed to complete the signal transition and establish valid logic levels at the receiver, providing sufficient setup and hold time while minimizing propagation delay.
Solution Approach 2:
The circuit changes the timing parameters of transistor activation and deactivation based on the delayed feedback signal. By adjusting when transistors are turned on and off relative to the input transition, the circuit optimizes both the propagation delay and the receiver setup/hold time, achieving fast transitions without compromising receiver reliability.
Data Source
AI summary
A repeater circuit. The repeater circuit includes two output circuits, two echo circuits, two activation circuits, and two deactivation circuits. Responsive to detecting a logical transition of an input signal, one of the activation circuits is configured to activate a corresponding output circuit, which is configured to drive an output signal on an output node. A corresponding echo circuit is configured to be activated and to drive an input node responsive to activation of the corresponding output circuit. A corresponding one of the deactivation circuits is configured to deactivate the corresponding output circuit after a delay time has elapsed, whereas the corresponding echo circuit is deactivated in response thereto. A keeper circuit is configured to continue providing the output signal on the output node after deactivation of the corresponding output circuit.