Output Buffer Impedance Calibration for Glitch-Free Memory Signaling
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Solution Overview
Problem
Conventional semiconductor devices experience signal integrity degradation due to impedance variation caused by temperature and voltage changes, leading to glitch generation and crosstalk, as calibration is typically performed only in non-communication durations, resulting in suboptimal resistance value adjustments during communication.
Innovation Solution
The implementation of a semiconductor device with a dual correction circuit system, comprising a non-communication correction circuit for coarse adjustment and a constant correction circuit for fine adjustment, allowing for continuous calibration of the output buffer's resistance value during both non-communication and communication periods, using a combination of transistors and resistors with power-of-two weights to minimize quantization errors and prevent glitch generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If calibration is performed only in non-communication durations, then glitch generation is prevented during calibration, but signal integrity degrades during communication due to impedance variation
Solution Approach 1:
The correction circuit is divided into two independent parts: a non-communication correction circuit for coarse adjustment and a constant correction circuit for fine adjustment. This segmentation allows each circuit to operate independently at different times and with different functions, preventing glitches during calibration while maintaining signal integrity during communication.
Solution Approach 2:
The non-communication correction circuit performs preliminary coarse adjustment of the resistance value during non-communication durations. This preliminary action prepares the system for subsequent fine adjustment by the constant correction circuit during communication, ensuring that major impedance variations are corrected before communication begins.
Solution Approach 3:
The constant correction circuit continuously adjusts the resistance value during communication periods to compensate for impedance variations caused by temperature and voltage changes. This continuous correction maintains signal integrity throughout the communication process without interrupting data transmission.
2Measurement precision
If a single correction circuit is used, then device complexity is reduced, but calibration precision is insufficient to maintain optimal resistance values under varying conditions
Solution Approach 1:
The correction function is segmented into two stages: coarse correction handling large resistance value changes and fine correction handling small resistance value changes. This segmentation enables high calibration precision by addressing different magnitude adjustments with specialized circuits, while keeping each individual circuit relatively simple.
Solution Approach 2:
The correction system dynamically switches between non-communication correction mode and constant correction mode based on communication state. During non-communication periods, the non-communication correction circuit operates; during communication periods, the constant correction circuit operates. This dynamic operation optimizes precision for each operating condition.
3Adaptability or versatility
If resistance elements are switched to adjust impedance, then impedance adjustment range is expanded, but glitch generation occurs during switching
Solution Approach 1:
The impedance adjustment function is segmented into coarse adjustment (non-communication correction) and fine adjustment (constant correction). This segmentation allows the system to achieve a wide impedance adjustment range through two stages while avoiding glitches by preventing switching operations during communication periods.
Solution Approach 2:
Major impedance adjustments are performed in advance during non-communication periods by the non-communication correction circuit. This preliminary adjustment establishes a baseline resistance value before communication begins, eliminating the need for switching operations during communication and thus preventing glitches.
Data Source
AI summary
A semiconductor device of an embodiment includes a buffer configured to perform data transmission by turning on and off a first output transistor group and a second output transistor group; a first correction circuit configured to calibrate a resistance value of the buffer by controlling an on-off state of each of first transistors of the first output transistor group; a second correction circuit configured to calibrate the resistance value of the buffer by controlling an on-off state of each of second transistors of the second output transistor group; and a control circuit configured to cause the calibration by the first correction circuit to be performed in a non-communication duration other than a duration of data transmission from the buffer and cause the calibration by the second correction circuit to be performed in a duration other than a duration of the calibration by the first correction circuit.