November 2004
Copyright Alliance Semiconductor. All rights reserved.
11/30/04, v 1.1
Alliance Semiconductor
1 of 19
3.3V 512K
18 Flow-through synchronous SRAM
AS7C33512FT18A
Features
Organization: 524,288 words 18 bits
Fast clock to data access:
7.5/8.5/10ns
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
3.3V core power supply
2.5V or 3.3V I/O operation with separate VDDQ
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
300
275
250
mA
Maximum standby current
110
100
90
mA
Maximum CMOS standby current (DC)
30
30
30
mA
Burst logic
ADV
ADSC
ADSP
CLK
LBO
CLK
CLR
CS
19
17
19
A[18:0]
19
Address
D
Q
CS
CLK
register
512K x 18
Memory
array
18
18
DQb
CLK
D
Q
Byte Write
registers
DQa
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,b]
2
CE0
CE1
CE2
BW
b
BW
a
OE
ZZ
OE
CLK
CLK
BWE
GWE
18
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AS7C33512FT18A
8 Mb Synchronous SRAM products
list
1,2
1 Core Power Supply: VDD = 3.3V + 0.165V
2 I/O Supply Voltage: VDDQ = 3.3V + 0.165V for 3.3V I/O
VDDQ = 2.5V + 0.125V for 2.5V I/O
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
512KX18
AS7C33512PFS18A
PL-SCD
166/133 MHz
256KX32
AS7C33256PFS32A
PL-SCD
166/133 MHz
256KX36
AS7C33256PFS36A
PL-SCD
166/133 MHz
512KX18
AS7C33512PFD18A
PL-DCD
166/133 MHz
256KX32
AS7C33256PFD32A
PL-DCD
166/133 MHz
256KX36
AS7C33256PFD36A
PL-DCD
166/133 MHz
512KX18
AS7C33512FT18A
FT
7.5/8.5/10 ns
256KX32
AS7C33256FT32A
FT
7.5/8.5/10 ns
256KX36
AS7C33256FT36A
FT
7.5/8.5/10 ns
512KX18
AS7C33512NTD18A
NTD-PL
166/133 MHz
256KX32
AS7C33256NTD32A
NTD-PL
166/133 MHz
256KX36
AS7C33256NTD36A
NTD-PL
166/133 MHz
512KX18
AS7C33512NTF18A
NTD-FT
7.5/8.5/10 ns
256KX32
AS7C33256NTF32A
NTD-FT
7.5/8.5/10 ns
256KX36
AS7C33256NTF36A
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.
AS7C33512FT18A
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Functional description
The AS7C33512FT18A is a high-performance CMOS 8-Mbit synchronous Static Random Access Memory (SRAM) device organized as
524,288 words 18 bits.
Fast cycle times of 8.5/10/12 ns with clock access times (t
CD
) of 7.5/8.5/10ns. 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 AS7C33512FT18A family operates from a core 3.3V power supply. I/Os use a separate power supply that can operate at 2.5V or 3.3V.
These devices are available in 100-pin TQFP.
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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AS7C33512FT18A
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]
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 18 bits. When high, BWE and BW[a,b] control write
enable.
BWE
I
SYNC
Byte write enable. Asserted low with GWE high to enable effect of BW[a,b] inputs.
BW[a,b]
I
SYNC
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.
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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