Cypress CY7C1527KV18, CY7C1516KV18, CY7C1520KV18, CY7C1518KV18 User Manual

72-Mbit DDR-II SRAM 2-Word
Burst Architecture
CY7C1516KV18, CY7C1527KV18 CY7C1518KV18, CY7C1520KV18

Features

Functional Description

72-Mbit Density (8M x 8, 8M x 9, 4M x 18, 2M x 36)
2-word Burst for reducing Address Bus Frequency
Double Data Rate (DDR) Interfaces
(data transferred at 666 MHz) at 333 MHz
Two Input Clocks (K and K) for precise DDR TimingSRAM uses rising edges only
Two Input Clocks for Output Data (C and C) to minimize Clock
Skew and Flight Time mismatches
Echo Clocks (CQ and CQ) simplify Data Capture in High Speed
Systems
Synchronous Internally Self-timed Writes
DDR-II operates with 1.5 Cycle Read Latency when DOFF is
asserted HIGH
Operates similar to DDR-I Device with 1 Cycle Read Latency
when DOFF
1.8V Core Power Supply with HSTL Inputs and Outputs
Variable Drive HSTL Output Buffers
Expanded HSTL Output Voltage (1.4V–VSupports both 1.5V and 1.8V IO supply
Available in 165-Ball FBGA Package (13 x 15 x 1.4 mm)
Offered in both Pb-free and non Pb-free Packages
JTAG 1149.1 compatible Test Access Port
Phase Locked Loop (PLL) for Accurate Data Placement
is asserted LOW
DD
)
The CY7C1516KV18, CY7C1527KV18, CY7C1518KV18, and CY7C1520KV18 are 1.8V Synchronous Pipelined SRAM equipped with DDR-II architecture. The DDR-II consists of an SRAM core with advanced synchronous peripheral circuitry and a 1-bit burst counter. Addresses for read and write are latched on alternate rising edges of the input (K) clock. Write data is registered on the rising edges of both K and K driven on the rising edges of C and C edge of K and K
if C/C are not provided. Each address location
if provided, or on the rising
. Read data is
is associated with two 8-bit words in the case of CY7C1516KV18 and two 9-bit words in the case of CY7C1527KV18 that burst sequentially into or out of the device. The burst counter always starts with a “0” internally in the case of CY7C1516KV18 and CY7C1527KV18. On CY7C1518KV18 and CY7C1520KV18, the burst counter takes in the least significant bit of the external address and bursts two 18-bit words in the case of CY7C1518KV18 and two 36-bit words in the case of CY7C1520KV18 sequentially into or out of the device.
Asynchronous inputs include an output impedance matching input (ZQ). Synchronous data outputs (Q, sharing the same physical pins as the data inputs D) are tightly matched to the two output echo clocks CQ/CQ
, eliminating the need for separately capturing data from each individual DDR SRAM in the system design. Output data clocks (C/C) enable maximum system clocking and data synchronization flexibility.
All synchronous inputs pass through input registers controlled by the K or K registers controlled by the C or C
input clocks. All data outputs pass through output
(or K or K in a single clock domain) input clocks. Writes are conducted with on-chip synchronous self-timed write circuitry.

Configurations

CY7C1516KV18 – 8M x 8
CY7C1527KV18 – 8M x 9
CY7C1518KV18 – 4M x 18
CY7C1520KV18 – 2M x 36
Table 1. Selection Guide
Description 333 MHz 300 MHz 250 MHz 200 MHz 167 MHz Unit
Maximum Operating Frequency 333 300 250 200 167 MHz
Maximum Operating Current x8 510 480 420 370 340 mA
x9 510 480 420 370 340
x18 520 490 430 380 340
x36 640 600 530 450 400
Cypress Semiconductor Corporation 198 Champion Court San Jose, CA 95134-1709 408-943-2600 Document Number: 001-00437 Rev. *E Revised March 30, 2009
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CY7C1516KV18, CY7C1527KV18 CY7C1518KV18, CY7C1520KV18

Logic Block Diagram (CY7C1516KV18)

Write Reg
Write Reg
CLK
A
(21:0)
Gen.
K
K
Control
Logic
Address
Register
Read Add. Decode
Read Data Reg.
R/W
Output
Logic
Reg.
Reg.
Reg.
8
16
8
NWS
[1:0]
V
REF
Write Add. Decode
8
22
C
C
8
LD
Control
R/W
DOFF
4M x 8 Array
4M x 8 Array
8
DQ
[7:0]
8
CQ
CQ
Write Reg
Write Reg
CLK
A
(21:0)
Gen.
K
K
Control
Logic
Address Register
Read Add. Decode
Read Data Reg.
R/W
Output
Logic
Reg.
Reg.
Reg.
9
18
9
BWS
[0]
V
REF
Write Add. Decode
9
22
C
C
9
LD
Control
R/W
DOFF
4M x 9 Array
4M x 9 Array
9
DQ
[8:0]
9
CQ
CQ

Logic Block Diagram (CY7C1527KV18)

Document Number: 001-00437 Rev. *E Page 2 of 30
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CY7C1516KV18, CY7C1527KV18 CY7C1518KV18, CY7C1520KV18

Logic Block Diagram (CY7C1518KV18)

Write Reg
Write Reg
CLK
A
(21:0)
Gen.
K
K
Control
Logic
Address Register
Read Add. Decode
Read Data Reg.
R/W
Output
Logic
Reg.
Reg.
Reg.
18
36
18
BWS
[1:0]
V
REF
Write Add. Decode
18
22
C
C
18
LD
Control
Burst
Logic
A0
A
(21:1)
R/W
DOFF
2M x 18 Array
2M x 18 Array
21
18
DQ
[17:0]
18
CQ
CQ
Write Reg
Write Reg
CLK
A
(20:0)
Gen.
K
K
Control
Logic
Address
Register
Read Add. Decode
Read Data Reg.
R/W
Output
Logic
Reg.
Reg.
Reg.
36
72
36
BWS
[3:0]
V
REF
Write Add. Decode
36
21
C
C
36
LD
Control
Burst Logic
A0
A
(20:1)
R/W
DOFF
1M x 36 Array
1M x 36 Array
20
36
DQ
[35:0]
36
CQ
CQ

Logic Block Diagram (CY7C1520KV18)

Document Number: 001-00437 Rev. *E Page 3 of 30
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CY7C1516KV18, CY7C1527KV18 CY7C1518KV18, CY7C1520KV18

Pin Configuration

Note
1. NC/144M and NC/288M are not connected to the die and can be tied to any voltage level.
The pin configurations for CY7C1516KV18, CY7C1527KV18, CY7C1518KV18, and CY7C1520KV18 follow.

165-Ball FBGA (13 x 15 x 1.4 mm) Pinout

CY7C1516KV18 (8M x 8)
1 2 3 4 5 6 7 8 9 10 11
A CQ AAR/WNWS
1
B NC NC NC A NC/288M K NWS
C NC NC NC V
D NC NC NC V
E NC NC DQ4 V
F NC NC NC V
G NC NC DQ5 V
H DOFF V
REF
V
DDQ
V
J NC NC NC V
K NC NC NC V
L NC DQ6 NC V
M NC NC NC V
N NC NC NC V
SS
SS
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
SS
SS
AAAVSSNC NC NC
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
AAAVSSNC NC NC
P NC NC DQ7 A A C A A NC NC NC
R TDO TCK A A A C AAATMSTDI
K NC/144M LD AACQ
0
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
ANCNCDQ3
V
SS
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
SS
[1]
NC NC NC
NC NC DQ2
NC NC NC
NC NC NC
V
DDQ
V
REF
NC DQ1 NC
NC NC NC
NC NC DQ0
NC NC NC
ZQ
CY7C1527KV18 (8M x 9)
1 2 3 4 5 6 7 8 9 10 11
A CQ AAR/WNC K NC/144M LD AACQ
B NC NC NC A NC/288M K BWS
C NC NC NC V
D NC NC NC V
E NC NC DQ4 V
F NC NC NC V
G NC NC DQ5 V
H DOFF V
REF
V
DDQ
V
J NC NC NC V
K NC NC NC V
L NC DQ6 NC V
M NC NC NC V
N NC NC NC V
SS
SS
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
SS
SS
AAAVSSNC NC NC
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
AAAVSSNC NC NC
0
ANCNCDQ3
V
V
V
V
V
V
V
V
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
V
SS
SS
NC NC NC
NC NC DQ2
NC NC NC
NC NC NC
V
DDQ
V
REF
NC DQ1 NC
NC NC NC
NC NC DQ0
NC NC NC
ZQ
P NC NC DQ7 A A C A A NC NC DQ8
R TDO TCK A A A C AAATMSTDI
Document Number: 001-00437 Rev. *E Page 4 of 30
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CY7C1516KV18, CY7C1527KV18 CY7C1518KV18, CY7C1520KV18
Pin Configuration (continued)
The pin configurations for CY7C1516KV18, CY7C1527KV18, CY7C1518KV18, and CY7C1520KV18 follow.
165-Ball FBGA (13 x 15 x 1.4 mm) Pinout
CY7C1518KV18 (4M x 18)
1 2 3 4 5 6 7 8 9 10 11
A CQ AAR/WBWS
1
B NC DQ9 NC A NC/288M K BWS
C NC NC NC V
D NC NC DQ10 V
E NC NC DQ11 V
F NC DQ12 NC V
G NC NC DQ13 V
H DOFF V
REF
V
DDQ
V
J NC NC NC V
K NC NC DQ14 V
L NC DQ15 NC V
M NC NC NC V
N NC NC DQ16 V
SS
SS
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
SS
SS
AA0AVSSNC DQ7 NC
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
AAAVSSNC NC NC
P NC NC DQ17 A A C A A NC NC DQ0
R TDO TCK A A A C AAATMSTDI
K NC/144M LD AACQ
0
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
ANCNCDQ8
V
SS
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
SS
[1]
NC NC NC
NC NC DQ6
NC NC DQ5
NC NC NC
V
DDQ
V
REF
NC DQ4 NC
NC NC DQ3
NC NC DQ2
NC DQ1 NC
ZQ
CY7C1520KV18 (2M x 36)
1 2 3 4 5 6 7 8 9 10 11
A CQ NC/144M A R/W BWS
B NC DQ27 DQ18 A BWS
C NC NC DQ28 V
D NC DQ29 DQ19 V
E NC NC DQ20 V
F NC DQ30 DQ21 V
G NC DQ31 DQ22 V
H DOFF V
REF
V
DDQ
V
J NC NC DQ32 V
K NC NC DQ23 V
L NC DQ33 DQ24 V
M NC NC DQ34 V
N NC DQ35 DQ25 V
SS
SS
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
SS
SS
AA0AVSSNC DQ17 DQ7
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
AAAVSSNC NC DQ10
2
3
K BWS
LD AACQ
1
KBWS0ANCNCDQ8
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
V
V
V
V
V
V
V
V
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
DDQ
V
SS
SS
NC NC DQ16
NC DQ15 DQ6
NC NC DQ5
NC NC DQ14
V
DDQ
V
REF
ZQ
NC DQ13 DQ4
NC DQ12 DQ3
NC NC DQ2
NC DQ11 DQ1
P NC NC DQ26 A A C A A NC DQ9 DQ0
R TDO TCK A A A C AAATMSTDI
Document Number: 001-00437 Rev. *E Page 5 of 30
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CY7C1516KV18, CY7C1527KV18 CY7C1518KV18, CY7C1520KV18

Pin Definitions

Pin Name I/O Pin Description
DQ
[x:0]
LD Input-
NWS NWS
BWS BWS BWS BWS
A, A0 Input-
R/W
C Input Clock Positive Input Clock for Output Data. C is used in conjunction with C
C
K Input Clock Positive Input Clock Input. The rising edge of K is used to capture synchronous inputs to the device
K
,
0 1
,
0
,
1
,
2 3
Input Output­Synchronous
Data Input Output Signals. Inputs are sampled on the rising edge of K and K clocks during valid write operations. These pins drive out the requested data when the read operation is active. Valid data is driven out on the rising edge of both the C and C mode. When read access is deselected, Q CY7C1516KV18 DQ CY7C1527KV18 DQ CY7C1518KV18 DQ CY7C1520KV18 DQ
[7:0] [8:0] [17:0] [35:0]
clocks during read operations or K and K when in single clock
are automatically tristated.
[x:0]
Synchronous Load. This input is brought LOW when a bus cycle sequence is defined. This definition
Synchronous
Input-
Synchronous
includes address and read/write direction. All transactions operate on a burst of 2 data. Nibble Write Select 0, 1 Active LOW (CY7C1516KV18 Only). Sampled on the rising edge of the K
and K
clocks during write operations. Used to select which nibble is written into the device during the current portion of the write operations. Nibbles not written remain unaltered. NWS0 controls D All the Nibble Write Selects are sampled on the same edge as the data. Deselecting a Nibble Write Select
and NWS1 controls D
[3:0]
[7:4]
.
ignores the corresponding nibble of data and it is not written into the device.
Input-
Synchronous
Byte Write Select 0, 1, 2, and 3 Active LOW. Sampled on the rising edge of the K and 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. CY7C1527KV18 BWS CY7C1518KV18 BWS0 controls D CY7C1520KV18 BWS0 controls D
.
D
[35:27]
All the Byte Write Selects are sampled on the same edge as the data. Deselecting a Byte Write Select
controls D
0
[8:0]
and BWS1 controls D
[8:0]
, BWS1 controls D
[8:0]
[17:9].
, BWS2 controls D
[17:9]
and BWS3 controls
[26:18]
ignores the corresponding byte of data and it is not written into the device.
Address Inputs. These address inputs are multiplexed for both read and write operations. Internally, the
Synchronous
device is organized as 8M x 8 (2 arrays each of 4M x 8) for CY7C1516KV18 and 8M x 9 (2 arrays each of 4M x9) for CY7C1527KV18, 4M x 18 (2 arrays each of 2M x 18) for CY7C1518KV18, and 2M x 36 (2 arrays each of 1M x 36) for CY7C1520KV18. CY7C1516KV18 – Since the least significant bit of the address internally is a “0,” only 22 external address inputs are needed to access the entire memory array. CY7C1527KV18 – Since the least significant bit of the address internally is a “0,” only 22 external address inputs are needed to access the entire memory array. CY7C1518KV18 – A0 is the input to the burst counter. These are incremented in a linear fashion internally. 22 address inputs are needed to access the entire memory array. CY7C1520KV18 – A0 is the input to the burst counter. These are incremented in a linear fashion internally. 21 address inputs are needed to access the entire memory array. All the address inputs are ignored when the appropriate port is deselected.
Input-
Synchronous
Synchronous Read or Write Input. When LD is LOW, this input designates the access type (read when R/W
is HIGH, write when R/W is LOW) for loaded address. R/W must meet the setup and hold times
around edge of K.
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.
Input Clock Negative Input Clock for Output Data. 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.
and to drive out data through Q edge of K.
when in single clock mode. All accesses are initiated on the rising
[x:0]
Input Clock Negative Input Clock Input. K is used to capture synchronous data being presented to the device and
to drive out data through Q
when in single clock mode.
[x:0]
Document Number: 001-00437 Rev. *E Page 6 of 30
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CY7C1516KV18, CY7C1527KV18 CY7C1518KV18, CY7C1520KV18
Pin Definitions (continued)
Pin Name I/O Pin Description
CQ Output Clock CQ Referenced with Respect to C. This is a free running clock and is synchronized to the input clock
for output data (C) of the DDR-II. In the single clock mode, CQ is generated with respect to K. The timing for the echo clocks is shown in the AC Timing table.
CQ
ZQ Input Output Impedance Matching Input. This input is used to tune the device outputs to the system data bus
DOFF
TDO Output TDO for JTAG.
TCK Input TCK Pin for JTAG.
TDI Input TDI Pin for JTAG.
TMS Input TMS Pin for JTAG.
NC N/A Not Connected to the Die. Can be tied to any voltage level.
NC/144M Input Not Connected to the Die. Can be tied to any voltage level.
NC/288M Input Not Connected to the Die. Can be tied to any voltage level.
V
REF
V
DD
V
SS
V
DDQ
Output Clock CQ Referenced with Respect to C. This is a free running clock and is synchronized to the input clock
Input PLL Turn Off Active LOW. Connecting this pin to ground turns off the PLL inside the device. The timing
Input-
Reference
Power Supply Power supply Inputs to the Core of the Device.
Ground Ground for the Device.
Power Supply Power Supply Inputs for the Outputs of the Device.
for output data (C for the echo clocks is shown in the AC Timing table.
impedance. CQ, CQ, and Q between ZQ and ground. Alternatively, this pin can be connected directly to V minimum impedance mode. This pin cannot be connected directly to GND or left unconnected.
in the PLL turned off operation differs from those listed in this data sheet. For normal operation, this pin is connected to a pull up through a 10 KΩ or less pull up resistor. The device behaves in DDR-I mode when the PLL is turned off. In this mode, the device can be operated at a frequency of up to 167 MHz with DDR-I timing.
Reference Voltage Input. Static input used to set the reference level for HSTL inputs, outputs, and AC measurement points.
) of the DDR-II. In the single clock mode, CQ is generated with respect to K. The timing
output impedance are set to 0.2 x RQ, where RQ is a resistor connected
[x:0]
, which enables the
DDQ
Document Number: 001-00437 Rev. *E Page 7 of 30
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CY7C1516KV18, CY7C1527KV18 CY7C1518KV18, CY7C1520KV18

Functional Overview

The CY7C1516KV18, CY7C1527KV18, CY7C1518KV18, and CY7C1520KV18 are synchronous pipelined Burst SRAMs equipped with a DDR interface, which operates with a read latency of one and a half cycles when DOFF When DOFF
pin is set LOW or connected to VSS the device
behaves in DDR-I mode with a read latency of one clock cycle.
Accesses are initiated on the rising edge of the positive input clock (K). All synchronous input timing is referenced from the rising edge of the input clocks (K and K referenced to the rising edge of the output clocks (C/C when in single clock mode).
All synchronous data inputs (D controlled by the rising edge of the input clocks (K and K synchronous data outputs (Q controlled by the rising edge of the output clocks (C/C
) pass through input registers
[x:0]
) pass through output registers
[x:0]
when in single clock mode).
All synchronous control (R/W, LD, BWS input registers controlled by the rising edge of the input clock (K).
CY7C1518KV18 is described in the following sections. The same basic descriptions apply to CY7C1516KV18, CY7C1527KV18, and CY7C1520KV18.

Read Operations

The CY7C1518KV18 is organized internally as a two arrays of 2M x 18. Accesses are completed in a burst of 2 sequential 18-bit data words. Read operations are initiated by asserting R/W HIGH and LD LOW at the rising edge of the positive input clock (K). The address presented to address inputs is stored in the read address register and the least significant bit of the address is presented to the burst counter. The burst counter increments the address in a linear fashion. Following the next K clock rise, the corresponding 18-bit word of data from this address location is driven onto the Q On the subsequent rising edge of C the next 18-bit data word
using C as the output timing reference.
[17:0]
from the address location generated by the burst counter is driven onto the Q the rising edge of the output clock (C or C
. The requested data is valid 0.45 ns from
[17:0]
single clock mode, 200 MHz, 250 MHz, and 300 MHz device). To maintain the internal logic, each read access must be allowed to complete. Read accesses can be initiated on every rising edge of the positive input clock (K).
When read access is deselected, the CY7C1518KV18 first completes the pending read transactions. Synchronous internal circuitry automatically tristates the output following the next rising edge of the positive output clock (C). This enables for a transition between devices without the insertion of wait states in a depth expanded memory.

Write Operations

Write operations are initiated by asserting R/W LOW and LD LOW at the rising edge of the positive input clock (K). The address presented to address inputs is stored in the write address register and the least significant bit of the address is presented to the burst counter. The burst counter increments the address in a linear fashion. On the following K clock rise, the data presented to D
is latched and stored into the 18-bit write
[17:0]
pin is tied HIGH.
) and all output timing is
, or K/K
). All
, or K/K
) inputs pass through
[0:X]
, or K and K when in
data register, provided BWS subsequent rising edge of the Negative Input Clock (K mation presented to D register, provided BWS of data are then written into the memory array at the specified
[17:0]
[1:0]
are both asserted active. On the
[1:0]
) the infor-
is also stored into the write data
are both asserted active. The 36 bits
location. Write accesses can be initiated on every rising edge of the positive input clock (K). Doing so pipelines the data flow such that 18 bits of data can be transferred into the device on every rising edge of the input clocks (K and K
).
When the write access is deselected, the device ignores all inputs after the pending write operations have been completed.

Byte Write Operations

Byte write operations are supported by the CY7C1518KV18. A write operation is initiated as described in the Write Operations section. The bytes that are written are determined by BWS
, which are sampled with each set of 18-bit data words.
BWS
1
Asserting the appropriate Byte Write Select input during the data
and
0
portion of a write latches the data being presented and writes it into the device. Deasserting the Byte Write Select input during the data portion of a write enables the data stored in the device for that byte to remain unaltered. This feature is used to simplify read, modify, or write operations to a byte write operation.

Single Clock Mode

The CY7C1518KV18 is used with a single clock that controls both the input and output registers. In this mode, the device recognizes only a single pair of input clocks (K and K
) that control both the input and output registers. This operation is identical to the operation if the device had zero skew between the K/K and C/C
clocks. All timing parameters remain the same in this mode.
To use this mode of operation, the user must tie C and C
HIGH at power on. This function is a strap option and not alterable during device operation.

DDR Operation

The CY7C1518KV18 enables high-performance operation through high clock frequencies (achieved through pipelining) and DDR mode of operation. The CY7C1518KV18 requires a single No Operation (NOP) cycle during transition from a read to a write cycle. At higher frequencies, some applications may require a second NOP cycle to avoid contention.
If a read occurs after a write cycle, address and data for the write are stored in registers. The write information must be stored because the SRAM cannot perform the last word write to the array without conflicting with the read. The data stays in this register until the next write cycle occurs. On the first write cycle after the read(s), the stored data from the earlier write is written into the SRAM array. This is called a posted write.
If a read is performed on the same address on which a write is performed in the previous cycle, the SRAM reads out the most current data. The SRAM does this by bypassing the memory array and reading the data from the registers.

Depth Expansion

Depth expansion requires replicating the LD control signal for each bank. All other control signals can be common between banks as appropriate.
Document Number: 001-00437 Rev. *E Page 8 of 30
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CY7C1516KV18, CY7C1527KV18 CY7C1518KV18, CY7C1520KV18

Programmable Impedance

Vterm = 0.75V
Vterm = 0.75V
R = 50ohms
R = 250ohms
LD# C C#R/W#
DQ A
K
LD# C C#R/W#
DQ A
K
SRAM#1
SRAM#2
R = 250ohms
BUS
MASTER
(CPU
or
ASIC)
DQ
Addresses
Cycle Start#
R/W# Return CLK Source CLK
Return CLK#
Source CLK# Echo Clock1/Echo Clock#1 Echo Clock2/Echo Clock#2
ZQ
CQ/CQ#
K#
ZQ
CQ/CQ#
K#
An external resistor, RQ, must be connected between the ZQ pin on the SRAM and V driver impedance. The value of RQ must be 5x the value of the intended line impedance driven by the SRAM. The allowable range of RQ to guarantee impedance matching with a tolerance of ±15% is between 175Ω and 350Ω output impedance is adjusted every 1024 cycles upon power up to account for drifts in supply voltage and temperature.
to allow the SRAM to adjust its output
SS
, with V
=1.5V. The
DDQ

Echo Clocks

Echo clocks are provided on the DDR-II to simplify data capture on high speed systems. Two echo clocks are generated by the DDR-II. CQ is referenced with respect to C and CQ is referenced with respect to C
. These are free running clocks and are synchro­nized to the output clock of the DDR-II. In single clock mode, CQ is generated with respect to K and CQ is generated with respect to K
. The timing for the echo clocks is shown in the Switching
Characteristics on page 23.

Application Example

Figure 1 shows two DDR-II used in an application.
Figure 1. Application Example
PLL
These chips use a PLL that is designed to function between 120 MHz and the specified maximum clock frequency. During power up, when the DOFF is tied HIGH, the PLL is locked after 20 μs of stable clock. The PLL can also be reset by slowing or stopping the input clock K and K However, it is not necessary to reset the PLL to lock to the desired frequency. The PLL automatically locks 20 μs after a stable clock is presented. The PLL may be disabled by applying ground to the DOFF pin. When the PLL is turned off, the device behaves in DDR-I mode (with one cycle latency and a longer access time).
for a minimum of 30 ns.
Document Number: 001-00437 Rev. *E Page 9 of 30
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