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GS8644V18(B/E)/GS8644V36(B/E)/GS8644V72(C)
4M x 18, 2M x 36, 1M x 72
72Mb S/DCD Sync Burst SRAMs
250 MHz
–
133MHz
1.8 V V
DD
1.8 V I/O
119-, 165-, & 209-Pin BGA
Commercial Temp
Industrial Temp
Rev:  1.03  11/2004
Specifications cited are subject to change without notice. For latest documentation see http://www.gsitechnology.com.
1/40
 2003, GSI Technology
Features
 FT pin for user-configurable flow through or pipeline operation
 Single/Dual Cycle Deselect selectable
 IEEE 1149.1 JTAG-compatible Boundary Scan
 ZQ mode pin for user-selectable high/low output drive
 1.8 V +10%/–10% core power supply and I/O
 LBO pin for Linear or Interleaved Burst mode
 Internal input resistors on mode pins allow floating mode pins
 Default to SCD x18/x36 Interleaved Pipeline mode
 Byte Write (BW) and/or Global Write (GW) operation
 Internal self-timed write cycle
 Automatic power-down for portable applications
 JEDEC-standard 119-, 165-, and 209-bump BGA package
Functional Description
Applications
The GS8644V18/36/72 is a 
75,497,472
-bit high performance 
synchronous SRAM with a 2-bit burst address counter. Although 
of a type originally developed for Level 2 Cache applications 
supporting high performance CPUs, the device now finds 
application in synchronous SRAM applications, ranging from 
DSP main store to networking chip set support. 
Controls 
Addresses, data I/Os, chip enable (E1), address burst control 
inputs (ADSP, ADSC, ADV), and write control inputs (Bx, BW, 
GW) are synchronous and are controlled by a positive-edge-
triggered clock input (CK). Output enable (G) and power down 
control (ZZ) are asynchronous inputs. Burst cycles can be initiated 
with either ADSP or ADSC inputs. In Burst mode, subsequent 
burst addresses are generated internally and are controlled by 
ADV. The burst address counter may be configured to count in 
either linear or interleave order with the Linear Burst Order (LBO) 
input. The Burst function need not be used. New addresses can be 
loaded on every cycle with no degradation of chip performance.
Flow Through/Pipeline Reads
The function of the Data Output register can be controlled by the 
user via the FT mode . Holding the FT mode pin low places the 
RAM in Flow Through mode, causing output data to bypass the 
Data Output Register. Holding FT high places the RAM in 
Pipeline mode, activating the rising-edge-triggered Data Output 
Register.
SCD and DCD Pipelined Reads
The GS8644V18/36/72 is a SCD (Single Cycle Deselect) and 
DCD (Dual Cycle Deselect)  pipelined synchronous SRAM.
 DCD 
SRAMs pipeline disable commands to the same degree as read 
commands. SCD SRAMs pipeline deselect commands one stage 
less than read commands. SCD RAMs begin turning off their 
outputs immediately after the deselect command has been 
captured in the input registers. DCD RAMs hold the deselect 
command for one full cycle and then begin turning off their 
outputs just after the second rising edge of clock. The user may 
configure this SRAM for either mode of operation using the SCD 
mode input. 
Byte Write and Global Write
Byte write operation is performed by using Byte Write enable 
(BW) input combined with one or more individual byte write 
signals (Bx). In addition, Global Write (GW) is available for 
writing all bytes at one time, regardless of the Byte Write control 
inputs. 
FLXDrive
The ZQ pin allows selection between high drive strength (ZQ low) 
for multi-drop bus applications and normal drive strength (ZQ 
floating or high) point-to-point applications. See the Output Driver 
Characteristics chart for details.
Sleep Mode
Low power (Sleep mode) is attained through the assertion (High) 
of the ZZ signal, or by stopping the clock (CK). Memory data is 
retained during Sleep mode. 
Core and Interface Voltages
The GS8644V18/36/72 operates on a 2.5 V or 3.3 V power 
supply. All input are 3.3 V and 2.5 V compatible. Separate output 
power (V
DDQ
) pins are used to decouple output noise from the 
internal circuits and are 3.3 V and 2.5 V compatible.
Parameter Synopsis
-250 -225 -200 -166 -150 -133 Unit
2.3
2.6
4.0
4.4
5.0
6.0
Pipeline
3-1-1-1
t
KQ
(x18/x36)
t
KQ
(x72)
tCycle
Curr (x18)
Curr (x36)
Curr (x72)
t
KQ
tCycle
Curr (x18)
Curr (x36)
Curr (x72)
2.5
2.7
2.7
2.8
2.9
2.9
3.3
3.3
6.7
3.5
3.5
7.5
ns
ns
ns
385
450
540
6.5
6.5
265
290
345
360
415
505
6.5
6.5
265
290
345
335
385
460
6.5
6.5
265
290
345
305
345
405
8.0
8.0
255
280
335
295
325
385
8.5
8.5
240
265
315
265
295
345
8.5
8.5
225
245
300
mA
mA
mA
ns
ns
mA
mA
mA
Flow 
Through
2-1-1-1