IC41C16105S
IC41LV16105S
ꢀunctional Description
Write Cycle
The IC41C16105S and IC41LV16105S is a CMOS DRAM
optimized for high-speed bandwidth, low power
applications. During READ or WRITE cycles, each bit is
uniquely addressed through the 10 address bits. These
are entered ten bits (A0-A9) at a time. 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 ten bits and CAS is used the
latter ten bits.
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, 1,024 refresh cycles are required in each
16 ms period. There are two ways to refresh the memory.
1. By clocking each of the 1,024 row addresses (A0
through A9) with RAS at least once every 16 ms. Any
read, write, read-modify-write or RAS-only cycle re-
freshes the addressed row.
The ICS41C16105S and IC41LV16105S has two CAS
controls, LCAS and UCAS. The LCAS and UCAS inputs
internally generates a CAS signal functioning in an iden-
tical manner to the single CAS input on the other 1M x 16
DRAMs. The key difference is that each CAS controls its
corresponding I/O tristate logic (in conjunction with OE
and WE and RAS). LCAS controls I/O0 through I/O7 and
UCAS controls I/O8 through I/O15.
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 10-bit counter provides the row
addresses and the external address inputs are ignored.
The IC41C16105S and IC41LV16105S CAS function is
determined by the first CAS (LCAS or UCAS) transitioning
LOW and the last transitioning back HIGH. The two CAS
controls give the IS41C16105L and IS41LV16105L both
BYTE READ and BYTE WRITE cycle capabilities.
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
The Self Refresh allows the user a dynamic refresh, data
retention mode at the extended refresh period of 128 ms.
i.e., 125 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 tRAS.
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.
The Self Refresh mode is terminated by driving RAS HIGH
for a minimum time of tRP. 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.
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.
However, if the DRAM controller utilizes a RAS-only or
burst refresh sequence, all 1,024 rows must be refreshed
within the average internal refresh rate, prior to the re-
sumption 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.
4
Integrated Circuit Solution Inc.
DR011-0A 05/23/2001
ICSI [ INTEGRATED CIRCUIT SOLUTION INC ]
