Pre-emphasis Signal Generator for Semiconductor Memory
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Solution Overview
Problem
Conventional semiconductor memory devices fail to adequately compensate for signal attenuation due to signal reflection, leading to reduced aperture windows and timing margins, especially in high-speed operations and multi-rank DRAM systems with increased parasitic components.
Innovation Solution
A semiconductor memory device with a pre-emphasis signal generator that includes an auto pulse generator, delay circuit, and delay control unit, which activates the secondary output driver with a pre-emphasis signal after a predetermined delay to compensate for signal reflection, improving slew rate characteristics and expanding the aperture window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-emphasis operation is performed continuously, then signal attenuation due to reflection is compensated, but noise is not effectively removed and timing margin is reduced
Solution Approach 1:
The pre-emphasis operation is performed in advance before the reflected signal returns to the output terminal. The delay circuit delays the pre-emphasis signal by a predetermined period matching the reflection time, so that the pre-emphasis effect is applied exactly when needed to compensate for upcoming signal attenuation, rather than continuously or reactively
Solution Approach 2:
The invention uses the known reflection characteristics of the transmission line to create a feedback mechanism. The delay circuit is configured with a delay period that matches the reflection time, creating a closed-loop effect where the pre-emphasis signal timing is automatically synchronized with the reflected signal return time, compensating for attenuation without requiring continuous monitoring
2Reliability
If pre-emphasis operation is performed at all times, then signal attenuation is compensated, but noise from parasitic components increases
Solution Approach 1:
The pre-emphasis operation is performed periodically only during specific time windows when signal reflection occurs, rather than continuously. The auto pulse generator and delay circuit create periodic pre-emphasis signals synchronized with the data signal transitions and reflection timing, eliminating unnecessary pre-emphasis operations that would generate noise from parasitic components
Solution Approach 2:
The system performs pre-emphasis operation in advance of the reflected signal return, using the predictable reflection timing to trigger pre-emphasis only when needed. This preliminary action based on known reflection characteristics avoids continuous operation and reduces noise from parasitic components while maintaining signal integrity
Data Source
AI summary
A semiconductor memory device includes a primary output driver which outputs a data signal through an output terminal; a secondary output driver which is connected to the output terminal and performs a pre-emphasis operation; and a pre-emphasis signal generator which outputs a pre-emphasis signal to enable the secondary output driver The pre-emphasis signal generator includes a auto pulse generator which generates an auto pulse in response to a transition of a control signal; a delay circuit which receives the auto pulse output from the auto pulse generator, delays the auto pulse by a predetermined period, and outputs a pre-emphasis signal; and a delay control unit which applies a delay control signal to the delay circuit and controls a delay amount of the delay circuit.