Packaged in a JEDEC Standard 100-pin plastic thin quad
flatpack (TQFP), 119 ball grid array (BGA) and 165 fine
pitch ball grid array (fBGA)
x
x
x
x
x
x
x
x
x
Description
The IDT71V3557/59 are 3.3V high-speed 4,718,592-bit (4.5 Mega-
bit) synchronous SRAMs organized as 128K x 36/256K x 18. They are
designed to eliminate dead bus cycles when turning the bus around
between reads and writes, or writes and reads. Thus they have been
given the name ZBT
TM
, or Zero Bus Turnaround.
Address and control signals are applied to the SRAM during one clock
cycle, and on the next clock cycle the associated data cycle occurs, be
it read or write.
The IDT71V3557/59 contain address, data-in and control signal
registers. The outputs are flow-through (no output data register). Output
enable is the only asynchronous signal and can be used to disable the
outputs at any given time.
A Clock Enable (CEN) pin allows operation of the IDT71V3557/59
to be suspended as long as necessary. All synchronous inputs are
ignored when (CEN) is high and the internal device registers will hold
their previous values.
There are three chip enable pins (CE
1
, CE
2
,
CE
2
) that allow the user
to deselect the device when desired. If any one of these three is not asserted
when ADV/LD is low, no new memory operation can be
initiated. However, any pending data transfers (reads or writes) will
be completed. The data bus will tri-state one cycle after chip is de-
selected or a write is initiated.
The IDT71V3557/59 have an on-chip burst counter. In the burst
mode, the IDT71V3557/59 can provide four cycles of data for a single
address presented to the SRAM. The order of the burst sequence is
defined by the
LBO
input pin. The
LBO
pin selects between linear and
interleaved burst sequence. The ADV/LD signal is used to load a new
external address (ADV/LD = LOW) or increment the internal burst counter
(ADV/LD = HIGH).
The IDT71V3557/59 SRAMs utilize IDT's latest high-performance
CMOS process and are packaged in a JEDEC standard 14mm x 20mm
100-pin thin plastic quad flatpack (TQFP) as well as a 119 ball grid array
(BGA) and a 165 fine pitch ball grid array (fBGA).
Pin Description Summary
A
0
-A
17
CE
1
, CE
2
,
CE
2
OE
R/W
CEN
BW
1
,
BW
2
,
BW
3
,
BW
4
CLK
ADV/LD
LBO
I/O
0
-I/O
31
, I/O
P1
-I/O
P4
V
DD
, V
DDQ
V
SS
Address Inputs
Chip Enables
Output Enable
Read/Write Signal
Clock Enable
Individual Byte Write Selects
Clock
Advance burst address / Load new address
Linear / Interleaved Burst Order
Data Input / Output
Core Power, I/O Power
Ground
Input
Input
Input
Input
Input
Input
Input
Input
Input
I/O
Supply
Supply
Synchronous
Synchronous
Asynchronous
Synchronous
Synchronous
Synchronous
N/A
Synchronous
Static
Synchronous
Static
Static
5282 tbl 01
ZBT and ZeroBus Turnaround are trademarks of Integrated Device Technology, Inc. and the architecture is supported by Micron Technology and Motorola Inc.
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