January 2005
Copyright Alliance Semiconductor. All rights reserved.
1/17/05, v 1.2
Alliance Semiconductor
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2.5V 1M
32/36 Flow-through synchronous SRAM
AS7C251MFT32A
AS7C251MFT36A
Features
Organization: 1,048,576 words 32 or 36 bits
Fast clock to data access:
7.5/8.5/10 ns
Fast OE access time: 3.5/4.0 ns
Fully synchronous flow-through operation
Asynchronous output enable control
Available in 100-pin TQFP package
Individual byte write and global write
Multiple chip enables for easy expansion
2.5V core power supply
Linear or interleaved burst control
Snooze mode for reduced power-standby
Common data inputs and data outputs
Logic block diagram
Selection guide
-75
-85
-10
Units
Minimum cycle time
8.5
10
12
ns
Maximum clock access time
7.5
8.5
10
ns
Maximum operating current
325
300
275
mA
Maximum standby current
130
130
130
mA
Maximum CMOS standby current (DC)
90
90
90
mA
A[19:0]
20
18
20
20
Q0
Q1
1M 32/36
Memory
array
Burst logic
CLK
CLR
CE
Address
D
Q
CE
CLK
DQ
d
CLK
D
Q
Byte write
registers
register
DQ
c
CLK
D
Q
Byte write
registers
DQ
b
CLK
D
Q
Byte write
registers
DQ
a
CLK
D
Q
Byte write
registers
Enable
CLK
D
Q
register
Enable
CLK
D
Q
delay
register
CE
Output
registers
Input
registers
Power
down
DQ[a:d]
4
32/36
GWE
BWE
BW
d
ADV
ADSC
ADSP
CLK
CE0
CE1
CE2
BW
c
BW
b
BW
a
OE
ZZ
LBO
OE
CLK
CLK
32/36
32/36
2
2
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Alliance Semiconductor
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AS7C251MFT32A
AS7C251MFT36A
2.5V 32 Mb Synchronous SRAM products list
1,2
1 Core Power Supply: VDD = 2.5V + 0.125V
2 I/O Supply Voltage: VDDQ = 2.5V + 0.125V
PL-SCD
:
Pipelined Burst Synchronous SRAM - Single Cycle Deselect
PL-DCD
:
Pipelined Burst Synchronous SRAM - Double Cycle Deselect
FT
:
Flow-through Burst Synchronous SRAM
NTD
1
-PL
:
Pipelined Burst Synchronous SRAM with NTD
TM
NTD-FT
:
Flow-through Burst Synchronous SRAM with NTD
TM
Org
Part Number
Mode
Speed
2MX18
AS7C252MPFS18A
PL-SCD
200/166/133 MHz
1MX32
AS7C251MPFS32A
PL-SCD
200/166/133 MHz
1MX36
AS7C251MPFS36A
PL-SCD
200/166/133 MHz
2MX18
AS7C252MPFD18A
PL-DCD
200/166/133 MHz
1MX32
AS7C251MPFD32A
PL-DCD
200/166/133 MHz
1MX36
AS7C251MPFD36A
PL-DCD
200/166/133 MHz
2MX18
AS7C252MFT18A
FT
7.5/8.5/10 ns
1MX32
AS7C251MFT32A
FT
7.5/8.5/10 ns
1MX36
AS7C251MFT36A
FT
7.5/8.5/10 ns
2MX18
AS7C252MNTD18A
NTD-PL
200/166/133 MHz
1MX32
AS7C251MNTD32A
NTD-PL
200/166/133 MHz
1MX36
AS7C251MNTD36A
NTD-PL
200/166/133 MHz
2MX18
AS7C252MNTF18A
NTD-FT
7.5/8.5/10 ns
1MX32
AS7C251MNTF32A
NTD-FT
7.5/8.5/10 ns
1MX36
AS7C251MNTF36A
NTD-FT
7.5/8.5/10 ns
1NTD: No Turnaround Delay. NTD
TM
is a trademark of Alliance Semiconductor Corporation. All trademarks mentioned in this document are the property of
their respective owners.
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Alliance Semiconductor
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AS7C251MFT32A
AS7C251MFT36A
Pin assignment
100-pin TQFP - top view
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
80
79
78
77
76
75
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
LBO
A
A
A
A
A
1
A0
NC
A
V
SS
V
DD
A
A
A
A
A
A
A
A
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
10
0
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
A
A
CE0
CE1
BWd
BWc
BWb
BW
a
CE2
V
DD
V
SS
CLK
GW
E
BWE
OE
AD
S
C
AD
S
P
AD
V
A
A
TQFP 14 x 20mm
A
NC/DQPc
DQc0
DQc1
V
DDQ
V
SSQ
DQc2
DQc3
DQc4
DQc5
V
SSQ
V
DDQ
DQc6
DQc7
NC
V
DD
NC
V
SS
DQd0
DQd1
V
DDQ
V
SSQ
DQd2
DQd3
DQd4
DQd5
V
SSQ
V
DDQ
DQd6
DQd7
NC/DQPd
DQPb/NC
DQb7
DQb6
V
DDQ
V
SSQ
DQb5
DQb4
DQb3
DQb2
V
SSQ
V
DDQ
DQb1
DQb0
V
SS
ZZ
DQa7
DQa6
V
DDQ
V
SSQ
DQa5
DQa4
DQa3
DQa2
V
SSQ
V
DDQ
DQa1
DQa0
DQPa/NC
V
DD
NC
Note: For pins 1, 30, 51, and 80, NC applies to the x32 configuration. DQPn applies to the x36 configuration.
AS7C251MFT32A
AS7C251MFT36A
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Functional description
The AS7C251MFT32A/36A is a high-performance CMOS 32-Mbit synchronous Static Random Access Memory (SRAM) device organized
as 1,048,576 words 32 or 36 bits.
Fast cycle times of 8.5/10/12 ns with clock access times (t
CD
) of 7.5/8.5/10 ns. Three chip enable (CE) inputs permit easy memory expansion.
Burst operation is initiated in one of two ways: the controller address strobe (ADSC), or the processor address strobe (ADSP). The burst
advance pin (ADV) allows subsequent internally generated burst addresses.
Read cycles are initiated with ADSP (regardless of WE and ADSC) using the new external address clocked into the on-chip address register
when ADSP is sampled low, the chip enables are sampled active, and the output buffer is enabled with OE. In a read operation, the data
accessed by the current address registered in the address registers by the positive edge of CLK are carried to the data-out buffer. ADV is
ignored on the clock edge that samples ADSP asserted, but is sampled on all subsequent clock edges. Address is incremented internally for
the next access of the burst when ADV is sampled low and both address strobes are high. Burst mode is selectable with the LBO input. With
LBO unconnected or driven high, burst operations use an interleaved count sequence. With LBO driven low, the device uses a linear count
sequence.
Write cycles are performed by disabling the output buffers with OE and asserting a write command. A global write enable GWE writes all 32/
36 regardless of the state of individual BW[a:d] inputs. Alternately, when GWE is high, one or more bytes may be written by asserting BWE
and the appropriate individual byte BWn signals.
BWn is ignored on the clock edge that samples ADSP low, but it is sampled on all subsequent clock edges. Output buffers are disabled when
BWn is sampled LOW regardless of OE. Data is clocked into the data input register when BWn is sampled low. Address is incremented
internally to the next burst address if BWn and ADV are sampled low.
Read or write cycles may also be initiated with ADSC instead of ADSP. The differences between cycles initiated with ADSC and ADSP are
as follows:
ADSP must be sampled high when ADSC is sampled low to initiate a cycle with ADSC.
WE signals are sampled on the clock edge that samples ADSC low (and ADSP high).
Master chip enable CE0 blocks ADSP, but not ADSC.
The AS7C251MFT32A and AS7C251MFT36A family operates from a core 2.5V power supply. These devices are available in 100-pin
TQFP package.
TQFP capacitance
*Guaranteed not tested
TQFP thermal resistance
Parameter
Symbol
Test conditions
Min
Max
Unit
Input capacitance
C
IN*
V
IN
= 0V
-
5
pF
I/O capacitance
C
I/O*
V
OUT
= 0V
-
7
pF
Description
Conditions
Symbol
Typical
Units
Thermal resistance
(junction to ambient)
1
1 This parameter is sampled
Test conditions follow standard test methods and
procedures for measuring thermal impedance,
per EIA/JESD51
1layer
JA
40
C/W
4layer
JA
22
C/W
Thermal resistance
(junction to top of case)
1
JC
8
C/W
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Alliance Semiconductor
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AS7C251MFT32A
AS7C251MFT36A
Signal descriptions
Snooze Mode
SNOOZE MODE is a low current, power-down mode in which the device is deselected and current is reduced to I
SB2
. The duration of
SNOOZE MODE is dictated by the length of time the ZZ is in a High state.
The ZZ pin is an asynchronous, active high input that causes the device to enter SNOOZE MODE.
When the ZZ pin becomes a logic High, I
SB2
is guaranteed after the time t
ZZI
is met. After entering SNOOZE MODE, all inputs except ZZ is
disabled and all outputs go to High-Z. Any operation pending when entering SNOOZE MODE is not guaranteed to successfully complete.
Therefore, SNOOZE MODE (READ or WRITE) must not be initiated until valid pending operations are completed. Similarly, when exiting
SNOOZE MODE during t
PUS
, only a DESELECT or READ cycle should be given while the SRAM is transitioning out of SNOOZE MODE.
Pin
I/O
Properties
Description
CLK
I
CLOCK
Clock. All inputs except OE, ZZ, and LBO are synchronous to this clock.
A,A0,A1
I
SYNC
Address. Sampled when all chip enables are active and when ADSC or ADSP are asserted.
DQ[a,b,c,d]
I/O
SYNC
Data. Driven as output when the chip is enabled and when OE is active.
CE0
I
SYNC
Master chip enable. Sampled on clock edges when ADSP or ADSC is active. When CE0 is inactive,
ADSP is blocked. Refer to the "Synchronous truth table" for more information.
CE1, CE2
I
SYNC
Synchronous chip enables, active high, and active low, respectively. Sampled on clock edges when
ADSC is active or when CE0 and ADSP are active.
ADSP
I
SYNC
Address strobe processor. Asserted low to load a new address or to enter standby mode.
ADSC
I
SYNC
Address strobe controller. Asserted low to load a new address or to enter standby mode.
ADV
I
SYNC
Advance. Asserted low to continue burst read/write.
GWE
I
SYNC
Global write enable. Asserted low to write all 32/36 bits. When high, BWE and BW[a:d] control write
enable.
BWE
I
SYNC
Byte write enable. Asserted low with GWE high to enable effect of BW[a:d] inputs.
BW[a,b,c,d]
I
SYNC
Write enables. Used to control write of individual bytes when GWE is high and BWE is low. If any of
BW[a:d] is active with GWE high and BWE low, the cycle is a write cycle. If all BW[a:d] are inactive,
the cycle is a read cycle.
OE
I
ASYNC
Asynchronous output enable. I/O pins are driven when OE is active and chip is in read mode.
LBO
I
STATIC
Selects Burst mode. When tied to V
DD
or left floating, device follows interleaved Burst order. When
driven Low, device follows linear Burst order. This signal is internally pulled High.
ZZ
I
ASYNC
Snooze. Places device in low power mode; data is retained. Connect to GND if unused.
NC
-
-
No connect
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