Periodic zq calibration using transaction-based self-refresh in multi-level ddr systems

Abstract

According to various aspects, a memory controller can schedule ZQ commands to periodically calibrate individual memory levels in a multi-level memory. The memory controller may schedule a ZQ short command every ZQ interval and record that the ZQ short command misses for the ZQ interval with respect to a memory stage in self-refresh mode. After the missed ZQ short command reaches the first threshold, a ZQ long command may be scheduled at the next ZQ interval, and if the memory stage exits the self-refresh mode and executes the ZQ long command, then normally ZQ behavior is recoverable. However, if the memory stage remains in the self-refresh mode until a missed ZQ long command reaches a second threshold, then the memory controller can toggle ZQ once the memory stage exits the self-refresh mode long command and skips the next ZQ calibration before resuming normal ZQ behavior.

Description

[0001] Cross-references to related applications [0002] This application claims PERIODIC ZQ CALIBRATION WITH TRAFFIC-BASED SELF-REFRESHIN A MULTI-RANK DDR SYSTEM, filed on May 31, 2016, entitled "PERIODIC ZQ CALIBRATION WITH TRAFFIC-BASED SELF-REFRESHIN A MULTI-RANK DDR SYSTEM ” of U.S. Provisional Patent Application No. 62 / 343,769, the contents of which are hereby expressly incorporated by reference in their entirety. technical field [0003] The present disclosure relates generally to memory systems, and in particular, to management operations to periodically calibrate a multi-level memory system supporting a traffic-based self-refresh mode. Background technique [0004] In double data rate (DDR) dynamic random access memory (DRAM) technology, the ZQ calibration command is used to periodically calibrate DRAM drive strength and termination values. For example, the memory controller may typically issue a ZQ calibration command to compensate for any system voltage and temp...

AI Technical Summary

Problems solved by technology

In such multi-stage systems, periodic ZQ calibrations must be issued to each stage, adding complexity in how each stage interacts with self-refresh mode relative to periodic ZQ commands

[0006] Thus, because ZQ calibration can take a significant amount of time due to stalling the entire memory channel and substantially impact memory latency, techniques are needed that increase the time that memory stages spend in self-refresh mode and reduce channel stall time, to improve memory power consumption and performance

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