DDR Memory ODT Control for Low-Power Signal Reflection Suppression
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Solution Overview
Problem
DDR2-SDRAM memory systems face increased power consumption when using on-die termination (ODT) to improve signal quality, especially when multiple memory devices are mounted in the same transmission path, which hampers high-speed data transfer due to signal reflection.
Innovation Solution
A memory control apparatus and method that accurately controls terminating circuits in memory devices to prevent signal reflection by selectively driving terminating means based on access type (read or write) and suppressing unnecessary ODT in non-accessed memory devices, using a memory control circuit with ODT control registers and logic circuits to manage ODT control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If on-die termination (ODT) is turned on in multiple memory devices to improve signal quality, then signal reflection is reduced, but power consumption increases
Solution Approach 1:
The patent applies local quality by enabling ODT selectively in specific memory devices based on access patterns. Instead of uniformly enabling ODT in all memory devices, the control circuit identifies which devices are being accessed and enables ODT only in those devices, thereby maintaining signal quality where needed while reducing power consumption in non-accessed devices.
Solution Approach 2:
The patent implements dynamics by making ODT configuration changeable based on operational conditions. The control circuit dynamically adjusts ODT settings according to access patterns, transitioning between different termination states (enabled/disabled) based on real-time memory access requirements, thus optimizing the balance between signal quality and power consumption.
2Productivity
If ODT is turned on in all memory devices to prevent signal reflection, then high-speed data transfer is enabled, but unnecessary ODT operations increase power consumption
Solution Approach 1:
The patent applies the taking out principle by extracting only the necessary ODT operations from the set of all memory devices. The control circuit identifies which specific memory devices require ODT based on access patterns and enables ODT only in those devices, removing unnecessary ODT operations from non-accessed devices to reduce power consumption while maintaining data transfer performance.
Solution Approach 2:
The patent implements partial action by applying ODT to only the subset of memory devices that are currently being accessed, rather than enabling it in all devices. This partial application of ODT is sufficient to maintain signal quality for active devices while avoiding the excessive power consumption that would result from enabling ODT in all devices regardless of access status.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for high signal quality while reducing power consumption by selectively enabling ODT only when necessary, thereby facilitating faster data transfer without increasing power usage across multiple memory devices.
Implementation Method 1
the impedance changes at, for example, connection points of a data bus and the memory devices. As a consequence, signal reflection generates electrical noise
Implementation Method 2
attaching a terminating resistor to the end of a transmission path
Data Source
AI summary
Each of a plurality of memories includes a terminating resistor for preventing signal reflection, and a memory control circuit includes an ODT control circuit for driving the terminating resistor of each memory, and a selector for selecting, from memories except for a memory to be accessed, at least one memory for which driving of the terminating resistor is to be suppressed, in accordance with the memory to be accessed.