Memory Input Buffer ODT Timing for Multi-Rank Signal Integrity
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Solution Overview
Problem
Conventional semiconductor memory devices face challenges in adjusting On Die Termination (ODT) timing effectively, particularly when multiple devices are arranged in a module, leading to impedance mismatch issues and signal reflection problems, especially at higher data transfer speeds.
Innovation Solution
A semiconductor memory device with an impedance adjusting unit, an ODT operating control unit, a delay adjusting unit, and an ODT timing control unit that dynamically adjusts impedance and timing based on the rank arrangement within a module, using decoding signals and ODT timing signals to optimize ODT operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the operating speed for delivering data is increased, then data transmission speed is improved, but signal reflection becomes serious causing data transmission instability
Solution Approach 1:
The patent changes the impedance parameter of the input buffer dynamically by controlling the impedance adjusting block with ODT control signals. This allows the input buffer impedance to match the transmission line impedance, reducing signal reflection and enabling stable high-speed data transmission
Solution Approach 2:
The patent makes the impedance of the input buffer adjustable and dynamic rather than fixed. The ODT control block dynamically controls the impedance adjusting block based on operating conditions, allowing the system to adapt to different data transmission speeds and maintain stability
2Reliability
If a termination resistor is added to match impedance, then signal reflection is reduced, but device complexity increases
Solution Approach 1:
The patent integrates the termination function directly into the input buffer circuitry through the impedance adjusting block, which can serve both as the input buffer and as the termination element. This eliminates the need for separate termination resistors and reduces overall circuit complexity
Solution Approach 2:
The patent merges the termination function with the input buffer function by making the input buffer impedance adjustable. The same circuit block (input buffer with impedance adjusting block) performs both signal buffering and impedance matching/termination, reducing the number of discrete components
3Manufacturing precision
If ODT timing is adjusted for different rank arrangements, then impedance matching is optimized, but control complexity increases
Solution Approach 1:
The patent enables the semiconductor memory device to automatically detect its rank arrangement and self-adjust the ODT timing accordingly. The device monitors its own operating conditions and dynamically configures its impedance without requiring complex external control circuits
Solution Approach 2:
The patent implements a feedback mechanism where the ODT control block monitors the operating conditions and rank arrangement, then automatically adjusts the impedance timing parameters. This closed-loop control optimizes impedance matching while keeping the control logic integrated and manageable
Data Source
AI summary
A semiconductor memory device according to the present invention can change adjusting timing of ODT operation in convenience and have an optimized ODT timing whether the semiconductor memory device is putted on ether rank of a module. The present invention includes an impedance adjusting unit for adjusting an impedance value of an input pad in response to an impedance selecting signal; an ODT operating control unit for controlling the impedance adjusting unit as generating the impedance selection signal using an decoding signal and an ODT timing signal; a delay adjusting unit for delaying an internal control clock for a predetermined timing to thereby generate the ODT timing signal; and an ODT timing control unit for controlling the delay adjusting unit to decide the value of the predetermined timing according to whether or not the semiconductor memory device is arranged to a first rank or a second rank in a module.