Memory Sampling Circuit for Row Hammer Target Refresh
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Solution Overview
Problem
Existing memory devices face issues with data loss due to the row hammering phenomenon, where specific word lines and adjacent lines are damaged by excessive activations, necessitating a target refresh operation that current sampling methods do not adequately address.
Innovation Solution
A semiconductor device and memory device incorporating a sampling circuit with a random number generation circuit, active counter, replacement control circuit, and sampling latch to randomly sample addresses, ensuring uniform probability and improved accuracy of target refresh operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a target refresh operation is performed on specific word lines to prevent row hammering, then data loss due to row hammering is reduced, but the complexity of address sampling and control increases
Solution Approach 1:
The address sampling process is divided into multiple independent stages: random number generation, active command counting, comparison logic, and latch control. Each stage is implemented as a separate functional block within the sampling circuit, allowing independent optimization and reducing overall complexity.
Solution Approach 2:
A dedicated sampling control circuit acts as an intermediary between the refresh control logic and the address latches. This intermediary circuit manages the complex sampling operations by coordinating random number generation, counting active commands, and controlling latch updates, thereby isolating the complexity from the main refresh control.
2Reliability
If random sampling of addresses is implemented to select word lines for target refresh, then the effectiveness of preventing row hammering is improved, but the time required for address processing increases
Solution Approach 1:
Random numbers are generated in advance and stored in the sampling control circuit before the refresh operation begins. Active commands are counted during the refresh period, and comparison results are prepared beforehand, allowing the actual address selection to occur rapidly when needed without delaying the refresh timing.
Solution Approach 2:
The sampling circuit continuously generates random numbers and counts active commands throughout the refresh period without interruption. This continuous operation ensures that address sampling is ready whenever a refresh operation is initiated, eliminating idle time and maintaining continuous productive action in the refresh process.
3Adaptability or versatility
If the number of active commands during target refresh period varies, then the adaptability of the refresh operation to row hammering conditions is improved, but the precision of uniform probability sampling decreases
Solution Approach 1:
The sampling circuit dynamically adjusts its operation based on the number of active commands detected during the refresh period. The replacement control signal is generated by comparing the counted active commands with pre-generated random numbers, allowing the sampling probability to adapt automatically to varying workload conditions while maintaining uniform distribution through the random number comparison mechanism.
Data Source
AI summary
A semiconductor device includes a random number generation circuit configured to generate a plurality of random signals according to a sampling signal; an active counter configured to count a number of inputs of an active command during a sampling period defined by the sampling signal to generate an active count signal; a replacement control circuit configured to compare the active count signal with each of the plurality of random signals to generate a replacement control signal; and a sampling latch configured to replace a sampling address with an input address according to the replacement control signal, and output the sampling address according to the sampling signal.