Memory and method for refreshing memory array

Abstract

A memory (10) includes a variable refresh control circuit (20) for controlling the refresh rate of a memory array (12) using a capacitor for data storage. In one embodiment, each test cell of a plurality of test memory cells (30, 32, 34, and 36) is refreshed at different rates. A monitor circuit (18) is provided for monitoring the stored logic state of each of the plurality of test memory cells, and in response, adjusting the refresh rate of the memory array (12). In another embodiment, a variable refresh control circuit (20') includes a plurality of test memory cells (70, 72, 74, and 76) thatare all refreshed at the same rate but each of the test memory cells (70, 72, 74, and 76) is implemented to have a different charge storage capacity than the other test memory cells. The monitor circuit (18) monitors the stored logic state of each of the plurality of test memory cells (70, 72, 74, and 76), and in response, adjusts a refresh rate of the memory array (12).

Description

technical field [0001] The present invention relates generally to integrated circuit memory, and more particularly to variable refresh control for dynamic random access memory (DRAM). Background technique [0002] Dynamic Random Access Memory (DRAM) is a well-known type of memory that relies on capacitance to store charges representing two logic states. Typically, each DRAM cell includes a capacitor and an access transistor. The charge stored in the capacitor leaks over time, so that the data stored by the DRAM cell needs to be periodically read and rewritten, or "refreshed." Periodic refresh operations require a large amount of power. [0003] The amount of charge leaked from a capacitor varies greatly with changes in voltage, temperature, and processing. Higher temperatures or voltages cause higher leakage than relatively lower temperatures or voltages. Also, changes in processing can cause larger leaks. Therefore, for a DRAM with a fixed refresh rate, memory cells mu...

AI Technical Summary

Problems solved by technology

A fixed refresh rate may require higher power consumption than is necessary for reliable operation of battery-backed memory

Images