Dynamic On-Die Termination Control for Memory Command Address Signal Integrity
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Solution Overview
Problem
Conventional static on-die termination (ODT) for command/address (CA) bus in memory systems does not effectively manage signal integrity and noise reduction during high-frequency operations, particularly in DDR5 synchronous DRAM modules.
Innovation Solution
A dynamic ODT mechanism is introduced, where local controllers generate ODT instructions based on chip select signals, switching on ODT at the CA input before receiving CA signals, ensuring proper termination and noise reduction by allowing sufficient time for instruction generation and maintaining ODT during signal reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If static on-die termination is used for CA bus, then device complexity is reduced, but signal integrity deteriorates during high-frequency operations
Solution Approach 1:
The patent implements dynamic on-die termination control where termination resistors are selectively activated based on operational conditions. The local controller receives chip select signals and generates ODT instructions to dynamically enable or disable termination for different memory ranks and time periods, allowing the system to adapt termination settings to current operational needs rather than using fixed static termination.
Solution Approach 2:
The patent changes the termination parameter (resistance activation) based on operational frequency and access patterns. By monitoring chip select signals and generating appropriate ODT instructions, the system adjusts termination resistance values dynamically to match high-frequency operation requirements, thereby improving signal integrity without excessive complexity.
2Reliability
If dynamic ODT activation is implemented, then signal integrity is improved, but device complexity increases
Solution Approach 1:
The local controller automatically generates ODT instructions in response to received chip select signals without requiring external control. When the local controller detects a chip select signal enabling access to a memory rank, it autonomously generates the corresponding ODT instruction to activate termination, and deactivates it when access is disabled, making the system self-managing and reducing overall control complexity.
Solution Approach 2:
The patent divides the memory system into multiple independent local controllers, each managing its own memory ranks and termination control. Each local controller independently receives chip select signals and generates ODT instructions for its assigned memory ranks, allowing distributed control that reduces the complexity burden on any single control unit while maintaining overall signal integrity.
3Reliability
If ODT instruction generation time is increased, then ODT activation timing is improved, but loss of time in signal processing increases
Solution Approach 1:
The local controller generates ODT instructions immediately upon receiving chip select signals, before the actual CA signals are processed. This preliminary action ensures that termination is activated in advance and remains stable during the entire signal reception period, eliminating timing issues without requiring extended processing time.
Solution Approach 2:
The patent maintains continuous ODT activation throughout the period when CA signals are being received. By keeping termination enabled for the entire duration of signal reception rather than just at discrete moments, the system ensures continuous signal integrity without requiring multiple activation/deactivation cycles that would increase processing time loss.
4Object-affected harmful factors
If ODT is activated for all memory ranks, then noise reduction is maximized, but loss of energy increases
Solution Approach 1:
The patent applies termination selectively to only those memory ranks that are currently active and receiving CA signals. By using chip select signals to identify which memory ranks need access, the local controller generates ODT instructions only for those specific ranks, providing noise reduction precisely where needed while leaving other ranks without termination to conserve energy.
Solution Approach 2:
The system periodically activates and deactivates ODT based on the periodic nature of memory access operations. Termination is enabled during periods when memory ranks are being accessed and disabled during periods when they are not, creating a periodic pattern of activation that balances noise reduction with energy conservation according to actual operational demands.
Data Source
AI summary
A memory system, comprising: a first plurality of memory ranks each having multiple memory cells; a second plurality of local controllers each coupled between one or more of the first plurality of memory ranks and a memory controller, the memory controller being configured to provide to a target local controller of the second plurality of local controllers, out of a first plurality of chip select (CS) signals, a target access CS signal enabling target access to a target memory rank of the first plurality of memory ranks coupled to the target local controller, and provide to the second plurality of local controllers, later than the target access CS signal, a command and address (CA) signal for addressing and accessing the multiple memory cells of the target memory rank; and wherein the target local controller is configured to generate, in response to receiving the target access CS signal, a target CA on-die termination (ODT) instruction switching on target CA ODT at its CA input at least for a period when the CA signal is being received from the memory controller.