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IC41LV44002ASL-60T Datasheet(PDF) 4 Page - Integrated Circuit Solution Inc |
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IC41LV44002ASL-60T Datasheet(HTML) 4 Page - Integrated Circuit Solution Inc |
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4 / 20 page  4 Integrated Circuit Solution Inc. DR026-0A 09/04/2001 IC41C44002A/IC41C44002AS(L) IC41LV44002A/IC41LV44002AS(L) Functional Description The IC41C44002A and IC41LV44002A are CMOS DRAMs optimized for high-speed bandwidth, low power applications. During READ or WRITE cycles, each bit is uniquely addressed through the 11 address bits. These are entered 11 bits (A0-A10) at a time for the 2K refresh device . The row address is latched by the Row Address Strobe ( RAS). The column address is latched by the Column Address Strobe ( CAS). RAS is used to latch the first 11 bits and CAS is used to latch the latter 11 bits. Memory Cycle A memory cycle is initiated by bring RAS LOW and it is terminated by returning both RAS and CAS HIGH. To ensures proper device operation and data integrity any memory cycle, once initiated, must not be ended or aborted before the minimum tRAS time has expired. A new cycle must not be initiated until the minimum precharge time tRP, tCP has elapsed. Read Cycle A read cycle is initiated by the falling edge of CAS or OE, whichever occurs last, while holding WE HIGH. The column address must be held for a minimum time specified by tAR. Data Out becomes valid only when tRAC, tAA, tCAC and tOE are all satisfied. As a result, the access time is dependent on the timing relationships between these parameters. Write Cycle A write cycle is initiated by the falling edge of CAS and WE, whichever occurs last. The input data must be valid at or before the falling edge of CAS or WE, whichever occurs last. Refresh Cycle To retain data, 2,048 refresh cycles are required in each 32 ms period. There are two ways to refresh the memory: 1. By clocking each of the 2,048 row addresses (A0 through A10) with RAS at least once every 32 ms. Any read, write, read-modify-write or RAS-only cycle re- freshes the addressed row. 2. Using a CAS-before-RAS refresh cycle. CAS-before- RAS refresh is activated by the falling edge of RAS, while holding CAS LOW. In CAS-before-RAS refresh cycle, an internal 11-bit counter provides the row ad- dresses and the external address inputs are ignored. CAS-before-RAS is a refresh-only mode and no data access or device selection is allowed. Thus, the output remains in the High-Z state during the cycle. Self Refresh Cycle(1) The Self Refresh allows the user a dynamic refresh, data retention mode at the extended refresh period of 64 ms. i. e., 32 µs per row when using distributed CBR refreshes. The feature also allows the user the choice of a fully static, low power data retention mode. The optional Self Refresh feature is initiated by performing a CBR Refresh cycle and holding RAS LOW for the specified tRASS. The Self Refresh mode is terminated by driving RAS HIGH for a minimum time of tRPS. This delay allows for the completion of any internal refresh cycles that may be in process at the time of the RAS LOW-to-HIGH transition. If the DRAM controller uses a distributed refresh sequence, a burst refresh is not required upon exiting Self Refresh. However, if the DRAM controller utilizes a RAS-only or burst refresh sequence, all 2048 rows must be refreshed within the average internal refresh rate, prior to the resump- tion of normal operation. Power-On After application of the VCC supply, an initial pause of 200 µs is required followed by a minimum of eight initial- ization cycles (any combination of cycles containing a RAS signal). During power-on, it is recommended that RAS track with VCC or be held at a valid VIH to avoid current surges. Note: 1.Self Refresh is for S version only. |
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