Encoded On-Die Termination for Read/Write Impedance Switching
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Solution Overview
Problem
Traditional on-die termination (ODT) systems in memory systems rely on binary signals, limiting the ability to change termination values between read and write operations, leading to suboptimal signal integrity and increased power consumption due to the need for channel bandwidth to adjust configuration registers.
Innovation Solution
Implementing serial encoding on the ODT signal line allows for multiple termination impedance values to be applied based on encoded signals, enabling unique read and write termination values without altering configuration registers, thereby reducing power consumption and improving signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional binary ODT signaling is used, then the system is simple to implement, but the ability to change termination values between read and write operations is limited
Solution Approach 1:
The patent changes the parameter of the ODT signal from binary (0 or 1) to multi-bit serial encoding that can represent multiple termination impedance values. This allows the system to select different termination values (e.g., 20 ohms, 40 ohms, 60 ohms, 80 ohms) for read and write operations independently, resolving the contradiction by enabling parameter versatility through encoded signaling rather than physical hardware changes.
Solution Approach 2:
The patent segments the ODT signal into multiple serial bits that can be transmitted sequentially. Instead of using a single binary signal, the termination value is broken down into multiple bits (e.g., 2 bits for 4 values, 3 bits for 8 values) that are sent in sequence over the same signal line, allowing multiple termination options without adding parallel signal lines or increasing physical complexity.
2Adaptability or versatility
If configuration registers are used to change ODT values, then termination values can be adjusted, but channel bandwidth is consumed and performance is penalized
Solution Approach 1:
The patent extracts the termination value selection function from the configuration register path and places it directly in the ODT control signal path. By encoding the termination value in the ODT enable signal itself, the system eliminates the need to write to configuration registers during normal read/write operations, thereby freeing up channel bandwidth for data transfer and avoiding performance penalties.
Solution Approach 2:
The patent performs preliminary encoding of the termination value into the ODT signal before the actual read/write operation begins. The termination value is predetermined and encoded into the ODT enable signal in advance, so that when the read or write operation starts, the correct termination is already in place without requiring any bandwidth-consuming register writes during the critical data path operation.
3Ease of operation
If the same termination value is used for read and write operations, then the system is simple to control, but signal integrity is suboptimal
Solution Approach 1:
The patent makes the termination value dynamic by allowing it to change based on the operation type (read or write) and the target package. The ODT enable signal is dynamically encoded with the appropriate termination value for each specific operation, enabling the system to optimize signal integrity for each transaction type while maintaining simple control through a single signal line that carries encoded information.
4Measurement precision
If multiple signals are used to control ODT values, then termination precision is improved, but power usage and complexity increase
Solution Approach 1:
The patent merges the termination value selection function into the existing ODT enable signal line by using serial encoding. Instead of adding separate control signals for different termination values, the system combines multiple pieces of information (enable state, termination value, timing) into a single encoded signal sequence, thereby achieving precise termination control without increasing the number of signal lines or power consumption associated with additional control circuits.
Data Source
AI summary
On-die termination (ODT) is triggered through a serial signal encoding on an ODT signal line instead of a simple binary enable signal. An ODT circuit applies one of multiple termination impedances based on the ODT signal encoding. An ODT enable signal line receives an ODT enable signal as multiple serial bits to encode the selected termination impedance, to cause the ODT circuit to apply the selected termination impedance.