Sense Amplifier Tail-Node Modulation for Charge Injection Noise
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Solution Overview
Problem
High-speed data interfaces in wired communication paths face challenges in controlling noise, particularly charge injection noise, which degrades signal quality due to charge injections at different phases of the clock signal in sense amplifiers.
Innovation Solution
The implementation of a sense amplifier with a strong-arm latch circuit and a modulation circuit that includes an additional current path to control voltage fluctuations at the common source node and a switchable capacitor to compensate for charge injection noise by storing and releasing opposite charges during different clock phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a sense amplifier is used to latch complementary signals at different phases of a clock signal, then data transmission capability is improved, but charge injection noise degrades signal quality
Solution Approach 1:
A modulation circuit is introduced as an intermediary between the clock signal and the sense amplifier's current path. This modulation circuit includes a switchable capacitor that is controlled by the clock signal to adjust the current path's impedance, thereby mediating the harmful interaction between the clock signal's charge injection and the sense amplifier's differential input signal.
Solution Approach 2:
The modulation circuit dynamically changes the impedance parameter of the current path connected to the tail node of the differential pair by switching capacitors in response to the clock signal. This parameter change allows the circuit to adapt to different clock phases, reducing charge injection noise during critical sampling periods while maintaining data transmission functionality.
2Measurement precision
If clock signals are used to control the sense amplifier for signal latching, then data sampling accuracy is improved, but voltage fluctuation at the common source node increases charge injection noise
Solution Approach 1:
The modulation circuit serves as an intermediary that decouples the direct connection between the clock signal and the current path. By inserting this circuit with switchable capacitors, voltage fluctuations at the common source node are reduced, preventing them from being converted into charge injection noise that would degrade the latched signal.
3Device complexity
If a traditional sense amplifier current path is used, then circuit simplicity is maintained, but charge injection noise from clock switching cannot be controlled
Solution Approach 1:
A modulation circuit is introduced as an intermediary between the clock signal and the sense amplifier's current path. This modulation circuit includes a switchable capacitor that is controlled by the clock signal to adjust the current path's impedance, thereby mediating the harmful interaction between the clock signal's charge injection and the sense amplifier's differential input signal.
Solution Approach 2:
The modulation circuit dynamically changes the impedance parameter of the current path connected to the tail node of the differential pair by switching capacitors in response to the clock signal. This parameter change allows the circuit to adapt to different clock phases, reducing charge injection noise during critical sampling periods while maintaining data transmission functionality.
Data Source
AI summary
An electronic device includes a sense amplifier. The sense amplifier includes a pair of load transistors cross-coupled to each other, a pair of input transistors coupled to the pair of load transistors, a first current path, and a second current path. The pair of input transistors is configured to receive a pair of input signals and enable generation of a pair of output signals from the pair of input signals during a duty cycle of a clock signal. The first current path is coupled to the pair of input transistors via a tail node and controlled by the clock signal to couple the tail node to a power supply and enable generation of the pair of output signals during the duty cycle of the clock signal. A second current path electrically couples the tail node to the power supply, independently of switching of the clock signal.