The AS7C31025B is a high-performance CMOS 1,048,576-bit Static Random Access Memory (SRAM) device organized as 131,072 x 8
bits. It is designed for memory applications where fast data access, low power, and simple interfacing are desired.
Equal address access and cycle times (t
AA
, t
RC
, t
WC
) of 10/12/15/20 ns with output enable access times (t
OE
) of 5, 6, 7, 8 ns are ideal for
high-performance applications. The chip enable input CE permits easy memory and expansion with multiple-bank memory systems.
When CE is high the device enters standby mode. A write cycle is accomplished by asserting write enable (WE) and chip enable (CE). Data
on the input pins I/O0 through I/O7 is written on the rising edge of WE (write cycle 1) or CE (write cycle 2). To avoid bus contention,
external devices should drive I/O pins only after outputs have been disabled with
output enable (
OE
) or write enable
(WE).
A read cycle is accomplished by asserting output enable (OE) and chip enable (CE), with write enable (WE) high. The chip drives I/O pins
with the data word referenced by the input address. When either chip enable or output enable is inactive or write enable is active, output
drivers stay in high-impedance mode.
All chip inputs and outputs are TTL-compatible, and operation is from a single 3.3 V supply. The AS7C31025B is packaged in common
industry standard packages.
Absolute maximum ratings
Parameter
Voltage on V
CC
relative to GND
Voltage on any pin relative to GND
Power dissipation
Storage temperature (plastic)
Ambient temperature with V
CC
applied
DC current into outputs (low)
Symbol
V
t1
V
t2
P
D
T
stg
T
bias
I
OUT
Min
–0.50
–0.50
–
–65
–55
–
Max
+5.0
V
CC
+ 0.5
1.0
+150
+125
20
Unit
V
V
W
o
C
o
C
mA
NOTE: Stresses greater than those listed under
Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress rating only and func-
tional operation of the device at these or any other conditions outside those indicated in the operational sections of this specification is not implied. Exposure
to absolute maximum rating conditions for extended periods may affect reliability.
Truth table
CE
H
L
L
L
WE
X
H
H
L
OE
X
H
L
X
Data
High Z
High Z
D
OUT
D
IN
Mode
Standby (I
SB
, I
SB1
)
Output disable (I
CC
)
Read (I
CC
)
Write (I
CC
)
Key: X = don’t care, L = low, H = high.
3/24/04, v. 1.3
Alliance Semiconductor
P. 2 of 9
AS7C31025B
®
Recommended operating conditions
Parameter
Supply voltage
Input voltage
Ambient operating temperature
V
IL
= -1.0V for pulse width less than 5ns
V
IH =
V
CC
+ 1.5V for pulse width less than 5ns
Symbol
V
CC
V
IH
V
IL
T
A
T
A
Min
3.0
2.0
–0.5
0
–40
Nominal
3.3
–
–
–
–
Max
3.6
V
CC
+ 0.5
0.8
70
85
Unit
V
V
V
o
C
o
C
DC operating characteristics (over the operating range)
当今的计算机外部设备，都在追求高速度和高通用性。为了满足用户的需求，以Intel为首的七家公司于1994年推出了USB（Universal Serial Bus，通用串行总线）总线协议，专用于低、中速的计算机外设。目前，USB端口已成为微机主板的标准端口；而在不久的将来，所有的微机外设，包括键盘、鼠标、显示器、打印机、数字相机、扫描仪和游戏柄等等，都将通过USB与主机相连。
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