IC41C82052
IC41LV82052
ꢀunctional Description
Refresh Cycle
The IC41C82052 and IC41LV82052 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 nine bits and CAS is used the latter ten bits.
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.
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.
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.
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).
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 tOEA are all satisfied. As a result, the access time is
dependent on the timing relationships between these
parameters.
During power-on, it is recommended that RAS track with
VCC or be held at a valid VIH to avoid current surges.
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.
Integrated Circuit Solution Inc.
DR015-0A 06/12/2001
3
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
