18Mb Pipelined
QDR™II SRAM
Burst of 2
Features
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IDT71P72804
IDT71P72604
Description
The IDT QDRII
TM
Burst of two SRAMs are high-speed synchro-
nous memories with independent, double-data-rate (DDR), read and
write data ports. This scheme allows simultaneous read and write
access for the maximum device throughput, with two data items passed
with each read or write. Four data word transfers occur per clock
cycle, providing quad-data-rate (QDR) performance. Comparing this
with standard SRAM common I/O (CIO), single data rate (SDR) de-
vices, a four to one increase in data access is achieved at equivalent
clock speeds. Considering that QDRII allows clock speeds in excess of
standard SRAM devices, the throughput can be increased well beyond
four to one in most applications.
Using independent ports for read and write data access, simplifies
system design by eliminating the need for bi-directional buses. All buses
associated with the QDRII are unidirectional and can be optimized for
signal integrity at very high bus speeds. The QDRII has scalable output
impedance on its data output bus and echo clocks, allowing the user to
tune the bus for low noise and high performance.
The QDRII has a single DDR address bus with multiplexed read
and write addresses. All read addresses are received on the first half of
the clock cycle and all write addresses are received on the second half
of the clock cycle. The read and write enables are received on the first
half of the clock cycle. The byte and nibble write signals are received on
both halves of the clock cycle simultaneously with the data they are
controlling on the data input bus.
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18Mb Density (1Mx18, 512kx36)
Separate, Independent Read and Write Data Ports
-
Supports concurrent transactions
Dual Echo Clock Output
2-Word Burst on all SRAM accesses
DDR (Double Data Rate) Multiplexed Address Bus
-
One Read and One Write request per clock cycle
DDR (Double Data Rate) Data Buses
-
Two word burst data per clock on each port
-
Four word transfers per clock cycle (2 word bursts
on 2 ports)
Depth expansion through Control Logic
HSTL (1.5V) inputs that can be scaled to receive signals
from 1.4V to 1.9V.
Scalable output drivers
-
Can drive HSTL, 1.8V TTL or any voltage level
from 1.4V to 1.9V.
-
Output Impedance adjustable from 35 ohms to 70
ohms
Commercial and Industrial Temperature Ranges
1.8V Core Voltage (V
DD
)
165-ball, 1.0mm pitch, 13mm x 15mm fBGA Package
JTAG Interface
Functional Block Diagram
(Note1)
D
(Note1)
DATA
REG
DATA
REG
(Note1)
WRITE DRIVER
SA
OUTPUT SELECT
(Note2)
SENSE AMPS
OUTPUT REG
ADD
REG
(Note2)
WRITE/READ DECODE
R
W
BWx
(Note3)
CTRL
LOGIC
18M
MEMORY
ARRAY
(Note4)
(Note4)
(Note1)
Q
K
K
C
C
CLK
GEN
SELECT OUTPUT CONTROL
6109 drw 16
CQ
CQ
Notes
1) Represents 18 signal lines for x18, and 36 signal lines for x36
2) Represents 19 address signal lines for x18, and 18 address signal lines for x36.
3) Represents 2 signal lines for x18, and 4r signal lines for x36.
4) Represents 36 signal lines for x18, and 72 signal lines for x36.
1
©2005 Integrated Device Technology, Inc. QDR SRAMs and Quad Data Rate RAMs comprise a new family of products developed by Cypress Semiconductor, IDT, and Micron Technology, Inc.
OCTOBER 2008
DSC-6109/0A
71P72804 (1M x 18-Bit) 71P72604 (512K x 36-Bit)
18 Mb QDR II SRAM Burst of 2
Commercial and IndustrialTemperature Range
The QDRII has echo clocks, which provide the user with a clock that
is precisely timed to the data output, and tuned with matching impedance
and signal quality. The user can use the echo clock for downstream
clocking of the data. Echo clocks eliminate the need for the user to
produce alternate clocks with precise timing, positioning, and signal quali-
ties to guarantee data capture. Since the echo clocks are generated by
the same source that drives the data output, the relationship to the data is
not significantly affected by voltage, temperature and process, as would
be the case if the clock were generated by an outside source.
All interfaces of the QDRII SRAM are HSTL, allowing speeds be-
yond SRAM devices that use any form of TTL interface. The interface
can be scaled to higher voltages (up to 1.9V) to interface with 1.8V
systems if necessary. The device has a V
DDQ
and a separate Vref,
allowing the user to designate the interface operational voltage, inde-
pendent of the device core voltage of 1.8V V
DD
.
The output impedance
control allows the user to adjust the drive strength to adapt to a wide
range of loads and transmission lines.
The device is capable of sustaining full bandwidth on both the input
and output ports simultaneously. All data is in two word bursts, with
addressing capability to the burst level.
Clocking
The QDRII SRAM has two sets of input clocks, namely the K,
K
clocks and the C,
C
clocks. In addition, the QDRII has an output “echo”
clock, CQ,
CQ.
The K and
K
clocks are the primary device input clocks. The K clock
is, used to clock in the control signals (R,
W
and
BWx),
the read ad-
dress, and the first word of the data burst during a write operation. The
K
clock is used to clock in the control signals (BWx), write address and
the second word of the data burst during a write operation. The K and
K
clocks are also used internally by the SRAM. In the event that the user
disables the C and
C
clocks, the K and
K
clocks will also be used to clock
the data out of the output register and generate the echo clock. The C
and
C
clocks may be used to clock the data out of the output register
during read operations and to generate the echo clocks. C and
C
must
be presented to the SRAM within the timing tolerances. The output data
from the QDRII will be closely aligned to the C and
C
input, through the
use of an internal DLL. When C is presented to the QDRII SRAM, the
DLL will have already internally clocked the first data word to arrive at
the device output simultaneously with the arrival of the
C
clock.
The C clock and second data word of the burst will also correspond.
Single Clock Mode
The QDRII SRAM may be operated with a single clock pair. C and
C
may be disabled by tying both signals high, forcing the outputs and
echo clocks to be controlled instead by the K and
K
clocks.
DLL Operation
The DLL in the output structure of the QDRII SRAM can be used to
closely align the incoming clocks C and
C
with the output of the data,
generating very tight tolerances between the two. The user may disable
the DLL by holding
Doff
low. With the DLL off, the C and
C
(or K and
K
if C and
C
are not used) will directly clock the output register of the
SRAM. With the DLL off, there will be a propagation delay from the time
the clock enters the device until the data appears at the output.
Echo Clock
The echo clocks, CQ and
CQ,
are generated by the C and
C
clocks
(or K,
K
if C,
C
are disabled). The rising edge of C generates the rising
edge of CQ, and the falling edge of
CQ.
The rising edge of
C
generates
the rising edge of
CQ
and the falling edge of CQ. This scheme improves
the correlation of the rising and falling edges of the echo clock and will
improve the duty cycle of the individual signals.
The echo clock is very closely aligned with the data, guaranteeing
that the echo clock will remain closely correlated with the data, within the
tolerances designated.
Read and Write Operations
QDRII devices internally store the two words of the burst as a single,
wide word and will retain their order in the burst. There is no ability to
address to the single word level or reverse the burst order; however, the
byte and nibble write signals can be used to prevent writing any indi-
vidual bytes, or combined to prevent writing one word of the burst.
Read operations are initiated by holding the read port select (R) low,
and presenting the read address to the address port during the rising
edge of K which will latch the address. The data will then be read and will
appear at the device output at the designated time in correspondence
with the C and
C
clocks.
Write operations are initiated by holding the write port select (W) low
and designating with the Byte Write inputs (BWx) which bytes are to be
written. The first word of the data must also be present on the data input
bus D[X:0]. Upon the rising edge of K the first word of the burst will be
latched into the input register. After K has risen, and the designated hold
times observed, the second half of the clock cycle is initiated by present-
ing the write address to the address bus SA[X:0], the
BWx
inputs for the
second data word of the burst, and the second data item of the burst to the
data bus D[X:0]. Upon the rising edge of
K,
the second word of the burst
will be latched, along with the designated address. Both the first and
second words of the burst will then be written into memory as designated
by the address and byte write enables.
Output Enables
The QDRII SRAM automatically enables and disables the Q[X:0]
outputs. When a valid read is in progress, and data is present at the
output, the output will be enabled. If no valid data is present at the output
(read not active), the output will be disabled (high impedance). The
echo clocks will remain valid at all times and cannot be disabled or turned
off. During power-up the Q outputs will come up in a high impedance
state.
Programmable Impedance
An external resistor, RQ, must be connected between the ZQ pin on
the SRAM and Vss to allow the SRAM to adjust its output drive imped-
ance. The value of RQ must be 5X the value of the intended drive
impedance of the SRAM. The allowable range of RQ to guarantee
impedance matching with a tolerance of +/- 10% is between 175 ohms
and 350 ohms, with V
DDQ
= 1.5V. The output impedance is adjusted
every 1024 clock cycles to correct for drifts in supply voltage and tem-
perature. If the user wishes to drive the output impedance of the SRAM
to it’s lowest value, the ZQ pin may be tied to V
DDQ
.
6.42
2
71P72804 (1M x 18-Bit) 71P72604 (512K x 36-Bit)
18 Mb QDR II SRAM Burst of 2
Commercial and IndustrialTemperature Range
Pin Definitions
Symbol
D[X:0]
Pin Function
Input
Synchronous
Description
Data input signals, sampled on the rising edge of K and
K
clocks during valid write operations
1M x 18 -- D[17:0]
512K x 36 -- D[35:0]
Byte Write Select 0, 1, 2, and 3 are active LOW. Sampled on the rising edge of the K and again on the rising edge of
K
clocks during write operations. Used to select which byte is written into the device during the current portion of the write
operations. Bytes not written remain unaltered. All the byte writes are sampled on the same edge as the data.
Deselecting a Byte Write Select will cause the corresponding byte of data to be ignored and not written in to the device.
1M x 18 --
BW
0
controls D[8:0] and
BW
1
controls D[17:9]
512K x 36 --
BW
0
controls D[8:0],
BW
1
controls D[17:9],
BW
2
controls D[26:18] and
BW
3
controls D[35:27]
Address Inputs. Read addresses are sampled on the rising edge of K clock during active read operations. Write
addresses are sampled on the rising edge of
K
clock during active write operations. These address inputs are
multiplexed, so that both a read and write operation can occur on the same clock cycle. These inputs are ignored when
the appropriate port is deselected.
Data Output signals. These pins drive out the requested data during a Read operation. Valid data is driven out on the rising
edge of both the C and
C
clocks during Read operations or K and
K
when operating in single clock mode. When the
Read port is deselected, Q[X:0] are automatically three-stated.
Write Control Logic active Low. Sampled on the rising edge of the positive input clock (K). When asserted active, a write
operation in initiated. Deasserting will deselect the Write port. Deselecting the Write port will cause
D[X:0] to be ignored.
Read Control Logic, active LOW. Sampled on the rising edge of Positive Input Clock (K). When active, a Read
operation is initiated. Deasserting will cause the Read port to be deselected. When deselected, the pending access is
allowed to complete and the output drivers are automatically three-stated following the next rising edge of the C clock.
Each read access consists of a burst of two sequential transfer.
Positive Output Clock Input. C is used in conjunction with
C
to clock out the Read data from the device. C and
C
can be
used together to deskew the flight times of various devices on the board back to the controller. See application example
for further details.
Negative Output Clock Input.
C
is used in conjunction with C to clock out the Read data from the device. C and
C
can
be used together to deskew the flight times of various devices on the board back to the controller. See application
example for further details.
Positive Input Clock Input. The rising edge of K is used to capture synchronous inputs to the device and to drive out
data through Q[X:0] when in single clock mode. All accesses are initiated on the rising edge of K.
Negative Input Clock Input.
K
is used to capture synchronous inputs being presented to the device and to drive out data
through Q[X:0] when in single clock mode.
Synchronous Echo clock outputs. The rising edges of these outputs are tightly matched to the synchronous data outputs
and can be used as a data valid indication. These signals are free running and do not stop when the output data is tri-
stated.
Output Impedance Matching Input. This input is used to tune the device outputs to the system data bus impedance.
Q[X:0] output impedance is set to 0.2 x RQ, where RQ is a resistor connected between ZQ and ground. Alternately, this
pin can be connected directly to V
DDQ
, which enables the minimum impedance mode. This pin cannot be connected
directly to GND or left unconnected.
6109 tbl 02a
BW
0
,
BW
1
BW
2
,
BW
3
Input
Synchronous
SA
Input
Synchronous
Q[X:0]
Output
Synchronous
W
Input
Synchronous
R
Input
Synchronous
C
Input Clock
C
Input Clock
K
K
Input Clock
Input Clock
CQ,
CQ
Output Clock
ZQ
Input
6.42
3
71P72804 (1M x 18-Bit) 71P72604 (512K x 36-Bit)
18 Mb QDR II SRAM Burst of 2
Commercial and IndustrialTemperature Range
Pin Definitions continued
Symbol
Pin Function
Description
DLL Turn Off. When low this input will turn off the DLL inside the device. The AC timings with the DLL turned off will be
different from those listed in this data sheet. There will be an increased propagation delay from the incidence of C and
C
to Q, or K and
K
to Q as configured. The propagation delay is not a tested parameter, but will be similar to the
propagation delay of other SRAM devices in this speed grade.
TDO pin for JTAG
TCK pin for JTAG.
TDI pin for JTAG. An internal resistor will pull TDI to V
DD
when the pin is unconnected.
TMS pin for JTAG. An internal resistor will pull TMS to V
DD
when the pin is unconnected.
Doff
Input
TDO
TCK
TDI
TMS
NC
V
REF
V
DD
V
SS
V
DDQ
Output
Input
Input
Input
No Connect No connects inside the package. Can be tied to any voltage level
Input
Reference
Power
Supply
Ground
Power
Supply
Reference Voltage input. Static input used to set the reference level for HSTL inputs and Outputs as well as AC
measurement points.
Power supply inputs to the core of the device. Should be connected to a 1.8V power supply.
Ground for the device. Should be connected to ground of the system.
Power supply for the outputs of the device. Should be connected to a 1.5V power supply for HSTL or scaled to the
desired output voltage.
6109 tbl 02b
6.42
4
71P72804 (1M x 18-Bit) 71P72604 (512K x 36-Bit)
18 Mb QDR II SRAM Burst of 2
Commercial and IndustrialTemperature Range
Pin Configuration IDT71P72804 (1M x 18)
1
A
B
C
D
E
F
G
H
J
K
L
M
N
P
R
CQ
NC
NC
NC
NC
NC
NC
Doff
NC
NC
NC
NC
NC
NC
TDO
2
V
SS/
SA
(3)
Q
9
NC
D
11
NC
Q
12
D
13
V
REF
NC
NC
Q
15
NC
D
17
NC
TCK
3
NC/
SA
(1)
D
9
D
10
Q
10
Q
11
D
12
Q
13
V
DDQ
D
14
Q
14
D
15
D
16
Q
16
Q
17
SA
4
W
SA
V
SS
V
SS
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
SS
V
SS
SA
SA
5
BW
1
NC
SA
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
SA
SA
SA
6
K
K
SA
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
SA
C
C
7
NC
BW
0
SA
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
SA
SA
SA
8
R
SA
V
SS
V
SS
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
SS
V
SS
SA
SA
9
SA
NC
NC
NC
NC
NC
NC
V
DDQ
NC
NC
NC
NC
NC
NC
SA
10
V
SS
/
SA
(2)
NC
Q
7
NC
D
6
NC
NC
V
REF
Q
4
D
3
NC
Q
1
NC
D
0
TMS
11
CQ
Q
8
D
8
D
7
Q
6
Q
5
D
5
ZQ
D
4
Q
3
Q
2
D
2
D
1
Q
0
TDI
6109 tbl 12b
165-ball FBGA Pinout
TOP VIEW
NOTES:
1. A3 is reserved for the 36Mb expansion address.
2. A10 is reserved for the 72Mb expansion address. This must be tied or driven to VSS on the 1M x 18 QDRII Burst of 2 (71P72804) devices.
3. A2 is reserved for the 144Mb expansion address. This must be tied or driven to VSS on the 1M x 18 QDRII Burst of 2 (71P72804) devices.
6.42
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