April 2004
®
AS7C252MFT18A
2.5V 2M
×
18 Flow-through synchronous SRAM
Features
•
•
•
•
•
•
•
•
•
•
•
Organization: 2,097152 words × 18 bits
Fast clock to data access: 6.5/7.5/8.5 ns
Fast OE access time: 3.5/3.5/4.0 ns
Fully synchronous flow-through operation
Asynchronous output enable control
Available in 100-pin TQFP package and 165-ball BGA
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
• Boundary scan using IEEE 1149.1 JTAG function
• NTD™
1
pipelined architecture available
(AS7C252MNTD18A, AS7C251MNTD32A/
AS7C251MNTD36A)
1 NTD™ is a trademark of Alliance Semiconductor Corporation. All
trademarks mentioned in this document are the property of their
respective owners.
Logic block diagram
LBO
CLK
ADV
ADSC
ADSP
A[20:0]
CLK
CS
CLR
Burst logic
Q
21
CS
Address
register
CLK
D
21
19 21
2M x 18
Memory
array
18
18
GWE
BW
b
BWE
BW
a
CE0
CE1
CE2
D
DQb
Q
CLK
D
DQa
Q
Byte Write
registers
Byte Write
CLK
D
registers
Enable
register
2
OE
Q
CE
CLK
ZZ
Output
registers
CLK
Input
registers
CLK
Power
down
D
Enable
Q
delay
register
CLK
OE
18
DQ[a,b]
Selection guide
Minimum cycle time
Maximum clock access time
Maximum operating current
Maximum standby current
Maximum CMOS standby current (DC)
-65
7.5
6.5
310
140
110
-75
8.5
7.5
290
130
110
-85
10
8.5
270
130
110
Units
ns
ns
mA
mA
mA
4/26/04, v 1.0
Alliance Semiconductor
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Copyright © Alliance Semiconductor. All rights reserved.
AS7C252MFT18A
®
Pin and ball assignment
100-pin TQFP - top view
A
A
CE0
CE1
NC
NC
BWb
BWa
CE2
V
DD
V
SS
CLK
GWE
BWE
OE
ADSC
ADSP
ADV
A
A
NC
NC
NC
V
DDQ
V
SSQ
NC
NC
DQb0
DQb1
V
SSQ
V
DDQ
DQb2
DQb3
NC
V
DD
NC
V
SS
DQb4
DQb5
V
DDQ
V
SSQ
DQb6
DQb7
DQPb
NC
V
SSQ
V
DDQ
NC
NC
NC
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
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
TQFP 14 x 20mm
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
A
NC
NC
V
DDQ
V
SSQ
NC
DQPa
DQa7
DQa6
V
SSQ
V
DDQ
DQa5
DQa4
V
SS
NC
V
DD
ZZ
DQa3
DQa2
V
DDQ
V
SSQ
DQa1
DQa0
NC
NC
V
SSQ
V
DDQ
NC
NC
NC
4/26/04, v 1.0
LBO
A
A
A
A
A1
A0
NC
A
V
SS
V
DD
A
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
Alliance Semiconductor
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AS7C252MFT18A
®
Ball assignment for 165-ball BGA for 2M X 18
1
A
B
C
D
E
F
G
H
J
K
L
M
N
P
R
2
3
4
BWb
5
6
7
8
9
10
11
NC
NC
NC
NC
NC
NC
NC
NC
DQb
DQb
DQb
DQb
DQPb
NC
LBO
A
A
NC
DQb
DQb
DQb
DQb
V
SS
NC
NC
NC
NC
NC
NC
A
CE0
CE1
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
NC
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
A
A
NC
BWa
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
Vss
Vss
Vss
Vss
NC
TDI
TMS
CE2
CLK
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
A
A1
1
A0
1
BWE
GWE
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
TDO
TCK
ADSC
OE
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
A
A
ADV
ADSP
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
NC
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
A
A
A
A
NC
NC
NC
NC
NC
NC
DQa
DQa
DQa
DQa
NC
A
A
A
NC
DQPa
DQa
DQa
DQa
DQa
ZZ
NC
NC
NC
NC
NC
A
A
NC
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
A
A
1 A0 and A1 are the two least significant bits (LSB) of the address field and set the internal burst counter if burst is desired.
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AS7C252MFT18A
®
Functional description
The AS7C252MFT18A is a high-performance CMOS 32-Mbit synchronous Static Random Access Memory (SRAM) device organized as
2,097152 words × 18 bits.
Fast cycle times of 7.5/8.5/10 ns with clock access times (t
CD
) of 6.5/7.5/8.5 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 18
bits regardless of the state of individual BW[a,b] 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
follow.
• 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 AS7C252MFT18A family operates from a core 2.5V power supply. These devices are available in a 100-pin TQFP and 165-ball BGA.
TQFP and BGA capacitance
Parameter
Input capacitance
I/O capacitance
Symbol
C
IN
C
I/O
Test conditions
V
IN
= 0V
V
OUT
= 0V
Min
-
-
Max
5
7
Unit
pF
pF
TQFP and BGA thermal resistance
Description
Thermal resistance
(junction to ambient)
1
Thermal resistance
(junction to top of case)
1
1 This parameter is sampled
Conditions
1–layer
Test conditions follow standard test methods and
procedures for measuring thermal impedance,
per EIA/JESD51
4–layer
Symbol
θ
JA
θ
JA
θ
JC
Typical
40
22
8
Units
°C/W
°C/W
°C/W
4/26/04, v 1.0
Alliance Semiconductor
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AS7C252MFT18A
®
Signal descriptions
Pin
CLK
A,A0,A1
DQ[a,b]
CE0
CE1, CE2
ADSP
ADSC
ADV
GWE
BWE
BW[a,b]
OE
LBO
TDO
TDI
TMS
TCK
ZZ
NC
I/O
I
I
I/O
I
I
I
I
I
I
I
I
I
I
O
I
I
I
I
-
Properties
CLOCK
SYNC
SYNC
SYNC
SYNC
SYNC
SYNC
SYNC
SYNC
SYNC
SYNC
ASYNC
STATIC
SYNC
SYNC
SYNC
Test Clock
ASYNC
-
Description
Clock. All inputs except OE, ZZ, and LBO are synchronous to this clock.
Address. Sampled when all chip enables are active and when ADSC or ADSP are asserted.
Data. Driven as output when the chip is enabled and when OE is active.
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.
Synchronous chip enables, active high, and active low, respectively. Sampled on clock edges when
ADSC is active or when CE0 and ADSP are active.
Address strobe processor. Asserted low to load a new address or to enter standby mode.
Address strobe controller. Asserted low to load a new address or to enter standby mode.
Advance. Asserted low to continue burst read/write.
Global write enable. Asserted low to write all 18 bits. When high, BWE and BW[a,b] control write
enable.
Byte write enable. Asserted low with GWE high to enable effect of BW[a,b] inputs.
Write enables. Used to control write of individual bytes when GWE is high and BWE is low. If any of
BW[a,b] is active with GWE high and BWE low, the cycle is a write cycle. If all BW[a,b] are inactive,
the cycle is a read cycle.
Asynchronous output enable. I/O pins are driven when OE is active and chip is in read mode.
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.
Serial data-out to the JTAG circuit. Delivers data on the negative edge of TCK (BGA only).
Serial data-in to the JTAG circuit. Sampled on the rising edge of TCK (BGA only).
This pin controls the Test Access Port state machine. Sampled on the rising edge of TCK (BGA only).
Test Clock. All inputs are sampled on the rising edge of TCK. All outputs are driven from the falling
edge of TCK.
Snooze. Places device in low power mode; data is retained. Connect to GND if unused.
No connects
Write enable truth table (per byte)
Function
Write All Bytes
Write Byte a
Write Byte b
Read
GWE
L
H
H
H
H
H
BWE
X
L
L
L
H
L
BWa
X
L
L
H
X
H
BWb
X
L
H
L
X
H
Key:
X = don’t care, L = low, H = high, n = a, b;
BWE
,
BWn
= internal write signal.
4/26/04, v 1.0
Alliance Semiconductor
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