STK16C88-3
256 Kbit (32K x 8) AutoStore+ nvSRAM
Features
Functional Description
■
Fast 35ns Read access and R/W cycle time
The Cypress STK16C88-3 is a 256Kb fast static RAM with a
nonvolatile element in each memory cell. The embedded
■
Directly replaces battery-backed SRAM modules such as
Dallas/Maxim DS1230W
nonvolatile elements incorporate QuantumTrap™ technology
producing the world’s most reliable nonvolatile memory. The
SRAM provides unlimited read and write cycles, while
independent, nonvolatile data resides in the highly reliable
QuantumTrap cell. Data transfers from the SRAM to the
nonvolatile elements (the STORE operation) takes place
automatically at power down. On power up, data is restored to
the SRAM (the RECALL operation) from the nonvolatile
memory. Both the STORE and RECALL operations are also
available under software control.
■
■
■
■
■
■
■
■
■
■
Automatic nonvolatile STORE on power loss
Nonvolatile STORE under Software control
Automatic RECALL to SRAM on power up
Unlimited Read/Write endurance
1,000,000 STORE cycles
100 year data retention
Single 3.3V+0.3V power supply
Commercial and Industrial Temperatures
28-pin (600 mil) PDIP package
RoHS compliance
Logic Block Diagram
Cypress Semiconductor Corporation
Document Number: 001-50594 Rev. **
•
198 Champion Court
•
San Jose, CA 95134-1709
•
408-943-2600
Revised January 29, 2009
STK16C88-3
If the STK16C88-3 is in a WRITE state at the end of power up
RECALL, the SRAM data is corrupted. To help avoid this
situation, a 10 Kohm resistor is connected either between WE
Device Operation
The AutoStore+ STK16C88-3 is a fast 32K x 8 SRAM that does
not lose its data on power down. The data is preserved in integral
QuantumTrap non-volatile storage elements when power is lost.
Automatic STORE on power down and automatic RECALL on
power up guarantee data integrity without the use of batteries.
and system VCC or between CE and system VCC
.
Software STORE
Data is transferred from the SRAM to the nonvolatile memory by
a software address sequence. The STK16C88-3 software
STORE cycle is initiated by executing sequential CE controlled
READ cycles from six specific address locations in exact order.
During the STORE cycle, an erase of the previous nonvolatile
data is first performed followed by a program of the nonvolatile
elements. When a STORE cycle is initiated, input and output are
disabled until the cycle is completed.
SRAM Read
The STK16C88-3 performs a READ cycle whenever CE and OE
are LOW while WE is HIGH. The address specified on pins A0–14
determines the 32,768 data bytes accessed. When the READ is
initiated by an address transition, the outputs are valid after a
delay of tAA (READ cycle 1). If the READ is initiated by CE or OE,
the outputs are valid at tACE or at tDOE, whichever is later (READ
cycle 2). The data outputs repeatedly respond to address
changes within the tAA access time without the need for transi-
tions on any control input pins, and remains valid until another
address change or until CE or OE is brought HIGH.
Because a sequence of READs from specific addresses is used
for STORE initiation, it is important that no other READ or WRITE
accesses intervene in the sequence. If they intervene, the
sequence is aborted and no STORE or RECALL takes place.
To initiate the software STORE cycle, the following READ
sequence is performed:
SRAM Write
1. Read address 0x0E38, Valid READ
2. Read address 0x31C7, Valid READ
3. Read address 0x03E0, Valid READ
4. Read address 0x3C1F, Valid READ
5. Read address 0x303F, Valid READ
6. Read address 0x0FC0, Initiate STORE cycle
A WRITE cycle is performed whenever CE and WE are LOW.
The address inputs must be stable prior to entering the WRITE
cycle and must remain stable until either CE or WE goes HIGH
at the end of the cycle. The data on the common IO pins DQ0–7
are written into the memory if it has valid tSD, before the end of
a WE controlled WRITE or before the end of an CE controlled
WRITE. Keep OE HIGH during the entire WRITE cycle to avoid
data bus contention on common IO lines. If OE is left LOW,
internal circuitry turns off the output buffers tHZWE after WE goes
LOW.
The software sequence is clocked with CE controlled READs.
When the sixth address in the sequence is entered, the STORE
cycle commences and the chip is disabled. It is important that
READ cycles and not WRITE cycles are used in the sequence.
It is not necessary that OE is LOW for a valid sequence. After the
tSTORE cycle time is fulfilled, the SRAM is again activated for
READ and WRITE operation.
AutoStore+ Operation
The STK16C88-3’s automatic STORE on power down is com-
pletely transparent to the system. The STORE initiation takes
less than 500 ns when power is lost (VCC<VSWITCH) at which point
the part depends only on its internal capacitor for STORE com-
pletion.
Software RECALL
Data is transferred from the nonvolatile memory to the SRAM by
a software address sequence. A software RECALL cycle is
initiated with a sequence of READ operations in a manner similar
to the software STORE initiation. To initiate the RECALL cycle,
the following sequence of CE controlled READ operations is
performed:
If the power supply drops faster than 20 μs/volt before Vcc
reaches Vswitch, then a 2.2 ohm resistor should be inserted
between Vcc and the system supply to avoid a momentary
excess of current between Vcc and internal capacitor.
1. Read address 0x0E38, Valid READ
2. Read address 0x31C7, Valid READ
3. Read address 0x03E0, Valid READ
4. Read address 0x3C1F, Valid READ
5. Read address 0x303F, Valid READ
6. Read address 0x0C63, Initiate RECALL cycle
In order to prevent unneeded STORE operations, automatic
STOREs are ignored unless at least one WRITE operation has
taken place since the most recent STORE or RECALL cycle.
Software initiated STORE cycles are performed regardless of
whether or not a WRITE operation has taken place.
Hardware RECALL (Power Up)
Internally, RECALL is a two step procedure. First, the SRAM data
is cleared, and then the nonvolatile information is transferred into
the SRAM cells. After the tRECALL cycle time, the SRAM is once
again ready for READ and WRITE operations. The RECALL
operation does not alter the data in the nonvolatile elements. The
nonvolatile data can be recalled an unlimited number of times.
During power up or after any low power condition (VCC<VRESET),
an internal RECALL request is latched. When VCC once again
exceeds the sense voltage of VSWITCH, a RECALL cycle is
automatically initiated and takes tHRECALL to complete.
Document Number: 001-50594 Rev. **
Page 3 of 14
STK16C88-3
Figure 3. Current Versus Cycle Time (WRITE)
Hardware Protect
The STK16C88-3 offers hardware protection against
inadvertent STORE operation and SRAM WRITEs during low
voltage conditions. When VCAP<VSWITCH, all externally
initiated STORE operations and SRAM WRITEs are inhibited.
Noise Considerations
The STK16C88-3 is a high speed memory. It must have a high
frequency bypass capacitor of approximately 0.1 µF
connected between VCC and VSS, using leads and traces that
are as short as possible. As with all high speed CMOS ICs,
careful routing of power, ground, and signals helps prevent
noise problems.
Low Average Active Power
CMOS technology provides the STK16C88-3 the benefit of
drawing significantly less current when it is cycled at times
relationship between ICC and READ or WRITE cycle time.
Worst case current consumption is shown for both CMOS and
TTL input levels (commercial temperature range, VCC = 5.5V,
100% duty cycle on chip enable). Only standby current is
drawn when the chip is disabled. The overall average current
drawn by the STK16C88-3 depends on the following items:
Best Practices
nvSRAM products have been used effectively for over 15
years. While ease-of-use is one of the product’s main system
values, experience gained working with hundreds of applica-
tions has resulted in the following suggestions as best
practices:
1. The duty cycle of chip enable
2. The overall cycle rate for accesses
3. The ratio of READs to WRITEs
4. CMOS versus TTL input levels
5. The operating temperature
6. The VCC level
■
The nonvolatile cells in an nvSRAM are programmed on the
test floor during final test and quality assurance. Incoming
inspection routines at customer or contract manufacturer’s
sites will sometimes reprogram these values. Final NV
patterns are typically repeating patterns of AA, 55, 00, FF,
A5, or 5A. End product’s firmware should not assume a NV
array is in a set programmed state. Routines that check
memory content values to determine first time system config-
urationand coldor warmboot status, should always program
a unique NV pattern (for example, complex 4-byte pattern of
46 E6 49 53 hex or more random bytes) as part of the final
system manufacturing test to ensure these system routines
work consistently.
7. IO loading
Figure 2. Current Versus Cycle Time (READ)
■
Power up boot firmware routines should rewrite the nvSRAM
into the desired state. While the nvSRAM is shipped in a
preset state, best practice is to again rewrite the nvSRAM
into the desired state as a safeguard against events that
might flip the bit inadvertently (program bugs or incoming
inspection routines).
Document Number: 001-50594 Rev. **
Page 4 of 14
STK16C88-3
Table 2. Software STORE/RECALL Mode Selection
A13 – A0
Mode
IO
Notes
CE
L
WE
H
0x0E38
0x31C7
0x03E0
0x3C1F
0x303F
0x0FC0
Read SRAM
Read SRAM
Read SRAM
Read SRAM
Read SRAM
Output Data
Output Data
Output Data
Output Data
Output Data
Output Data
Nonvolatile STORE
L
H
0x0E38
0x31C7
0x03E0
0x3C1F
0x303F
0x0C63
Read SRAM
Read SRAM
Read SRAM
Read SRAM
Read SRAM
Output Data
Output Data
Output Data
Output Data
Output Data
Output Data
Nonvolatile RECALL
Notes
1. The six consecutive addresses must be in the order listed. WE must be high during all six consecutive CE controlled cycles to enable a nonvolatile cycle.
2. While there are 15 addresses on the STK16C88-3, only the lower 14 are used to control software modes.
Document Number: 001-50594 Rev. **
Page 5 of 14
STK16C88-3
Voltage on DQ0-7 ...................................–0.5V to Vcc + 0.5V
Power Dissipation ......................................................... 1.0W
DC output Current (1 output at a time, 1s duration) .... 15 mA
Operating Range
Maximum Ratings
Exceeding maximum ratings may shorten the useful life of the
device. These user guidelines are not tested.
Storage Temperature .................................–65°C to +150°C
Temperature under bias..............................–55°C to +125°C
Supply Voltage on VCC Relative to GND.......... –0.5V to 4.5V
Voltage on Input Relative to Vss............–0.6V to VCC + 0.5V
Range
Commercial
Industrial
Ambient Temperature
0°C to +70°C
VCC
3.0V to 3.6V
3.0V to 3.6V
-40°C to +85°C
DC Electrical Characteristics
Over the operating range (VCC = 3.0V to 3.6V)
Parameter
Description
Test Conditions
Min
Max Unit
ICC1
Average VCC Current
tRC = 35 ns
Dependent on output loading and cycle rate.
Values obtained without output loads.
Commercial
50
52
mA
mA
Industrial
I
OUT = 0 mA.
ICC2
ICC3
Average VCC Current
during STORE
All Inputs Do Not Care, VCC = Max
Average current for duration tSTORE
3
8
mA
mA
Average VCC Current at WE > (VCC – 0.2V). All other inputs cycling.
tRC= 200 ns, 5V, 25°C Dependent on output loading and cycle rate. Values obtained
Typical
without output loads.
[3]
ISB1
Average VCC Current
(Standby, Cycling TTL
Input Levels)
tRC=35ns, CE > VIH
Commercial
Industrial
18
19
mA
mA
[3]
ISB2
VCC Standby Current
(Standby, Stable CMOS
Input Levels)
CE > (VCC – 0.2V). All others VIN < 0.2V or > (VCC – 0.2V).
1
mA
IIX
Input Leakage Current VCC = Max, VSS < VIN < VCC
-1
-1
+1
+1
μA
IOZ
Off State Output
Leakage Current
VCC = Max, VSS < VIN < VCC, CE or OE > VIH or WE < VIL
μA
VIH
VIL
Input HIGH Voltage
2.2
VCC
0.5
+
V
V
Input LOW Voltage
VSS
0.5
–
0.8
VOH
VOL
Output HIGH Voltage
Output LOW Voltage
IOUT = –4 mA
IOUT = 8 mA
2.4
V
V
0.4
Data Retention and Endurance
Parameter
DATAR
Description
Min
100
Unit
Years
K
Data Retention
NVC
Nonvolatile STORE Operations
1,000
Note
3. CE > V will not produce standby current levels until any nonvolatile cycle in progress has timed out.
IH
Document Number: 001-50594 Rev. **
Page 6 of 14
STK16C88-3
Capacitance
Parameter
Description
Input Capacitance
Output Capacitance
Test Conditions
TA = 25°C, f = 1 MHz,
CC = 0 to 3.0 V
Max
5
Unit
pF
CIN
V
COUT
7
pF
Thermal Resistance
In the following table, the thermal resistance parameters are listed.[4]
Parameter
Description
Test Conditions
28-PDIP
Unit
ΘJA
Thermal Resistance
(Junction to Ambient)
Test conditions follow standard test methods and proce-
dures for measuring thermal impedance, per EIA /
JESD51.
TBD
°C/W
ΘJC
Thermal Resistance
(Junction to Case)
TBD
°C/W
Figure 4. AC Test Loads
R1 317Ω
3.3V
Output
R2
30 pF
351Ω
AC Test Conditions
Input Pulse Levels..................................................0 V to 3 V
Input Rise and Fall Times (10% - 90%)........................ <5 ns
Input and Output Timing Reference Levels................... 1.5 V
Note
4. These parameters are guaranteed by design and are not tested.
Document Number: 001-50594 Rev. **
Page 7 of 14
STK16C88-3
AC Switching Characteristics
SRAM Read Cycle
Parameter
35 ns
Description
Chip Enable Access Time
Unit
Cypress
Alt
Min
Max
Parameter
tACE
tELQV
tAVAV, ELEH
tAVQV
35
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
tRC
t
Read Cycle Time
35
[6]
tAA
tDOE
Address Access Time
35
15
tGLQV
Output Enable to Data Valid
Output Hold After Address Change
Chip Enable to Output Active
Chip Disable to Output Inactive
Output Enable to Output Active
Output Disable to Output Inactive
Chip Enable to Power Active
Chip Disable to Power Standby
[6]
tOHA
tAXQX
5
5
[7]
[7]
[7]
[7]
tLZCE
tHZCE
tLZOE
tHZOE
tELQX
tEHQZ
13
13
35
tGLQX
0
0
tGHQZ
[4]
tPU
tELICCH
tEHICCL
tPD
Switching Waveforms
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Notes
5. WE must be HIGH during SRAM Read Cycles.
6. I/O state assumes CE and OE < V and WE > V ; device is continuously selected.
IL
IH
7. Measured ±200 mV from steady state output voltage.
Document Number: 001-50594 Rev. **
Page 8 of 14
STK16C88-3
Table 3. SRAM Write Cycle
Parameter
35 ns
Description
Unit
Cypress
Parameter
Alt
Min
Max
tWC
tAVAV
tWLWH, WLEH
tELWH, ELEH
tDVWH, DVEH
tWHDX, EHDX
tAVWH, AVEH
tAVWL, AVEL
tWHAX, EHAX
tWLQZ
tWHQX
Write Cycle Time
Write Pulse Width
35
25
25
12
0
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
tPWE
tSCE
tSD
tHD
tAW
tSA
tHA
tHZWE
tLZWE
t
t
Chip Enable To End of Write
Data Setup to End of Write
t
t
Data Hold After End of Write
Address Setup to End of Write
Address Setup to Start of Write
Address Hold After End of Write
Write Enable to Output Disable
Output Active After End of Write
t
25
0
t
t
0
[7]
13
5
Switching Waveforms
tWC
ADDRESS
CE
tHA
tSCE
tAW
tSA
tPWE
WE
tHD
tSD
DATA VALID
DATA IN
tHZWE
tLZWE
HIGH IMPEDANCE
PREVIOUS DATA
DATA OUT
tWC
ADDRESS
tHA
tSCE
tSA
CE
WE
tAW
tPWE
tSD
tHD
DATA IN
DATA VALID
HIGH IMPEDANCE
DATA OUT
Notes
8. If WE is Low when CE goes Low, the outputs remain in the high impedance state.
9.
CE or WE must be greater than V during address transitions.
IH
Document Number: 001-50594 Rev. **
Page 9 of 14
STK16C88-3
AutoStorePlus or Power Up RECALL
STK16C88-3
Parameter
Alt
Description
Unit
Min
Max
[10]
tHRECALL
tRESTORE
tHLHZ
Power up RECALL Duration
STORE Cycle Duration
550
10
μs
ms
ns
V
tSTORE
tstg
Power-down AutoStore Slew Time to Ground
Low Voltage Reset Level
500
2.7
VRESET
2.4
VSWITCH
Low Voltage Trigger Level
2.95
V
Switching Waveforms
Figure 9. AutoStorePlus/Power Up RECALL
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Notes
10. t
starts from the time V rises above V .
SWITCH
HRECALL
CC
Document Number: 001-50594 Rev. **
Page 10 of 14
STK16C88-3
Software Controlled STORE/RECALL Cycle
35 ns
Parameter
Alt
Description
Unit
Min
35
0
Max
tRC
tAVAV
tAVEL
tELEH
tELAX
STORE/RECALL Initiation Cycle Time
Address Setup Time
ns
ns
ns
ns
μs
[11]
tSA
tCW
Clock Pulse Width
25
20
tHACE
Address Hold Time
tRECALL
RECALL Duration
20
Switching Waveforms
tRC
tRC
ADDRESS # 1
ADDRESS # 6
ADDRESS
CE
tSA
tSCE
tHACE
OE
t
STORE / tRECALL
HIGH IMPEDANCE
DATA VALID
DATA VALID
DQ (DATA)
Notes
11. The software sequence is clocked on the falling edge of CE without involving OE (double clocking will abort the sequence).
12. The six consecutive addresses must be read in the order listed in the Mode Selection table. WE must be HIGH during all six consecutive cycles.
Document Number: 001-50594 Rev. **
Page 11 of 14
STK16C88-3
Part Numbering Nomenclature
STK16C88 - 3W F 35 I
Temperature Range:
Blank - Commercial (0 to 70°C)
I - Industrial (-40 to 85°C)
Speed:
35 - 35 ns
Lead Finish
F = 100% Sn (Matte Tin)
Package:
W = Plastic 28-pin 600 mil DIP
Ordering Information
Speed
Operating
Range
Package Diagram
Package Type
28-pin PDIP
(ns)
Ordering Code
STK16C88-3WF35
STK16C88-3WF35I
35
51-85017
Commercial
Industrial
All parts are Pb-free. The above table contains Final information. Please contact your local Cypress sales representative for availability of these parts
Document Number: 001-50594 Rev. **
Page 12 of 14
STK16C88-3
Package Diagrams
Figure 11. 28-Pin (600 Mil) PDIP (51-85017)
51-85017 *B
Document Number: 001-50594 Rev. **
Page 13 of 14
STK16C88-3
Document History Page
Document Title: STK16C88-3 256 Kbit (32K x 8) AutoStore+ nvSRAM
Document Number: 001-50594
Orig. of
Change
Submission
Date
Rev.
ECN No.
Description of Change
**
2625096
GVCH/PYRS
12/19/08
New data sheet
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© Cypress Semiconductor Corporation, 2008-2009. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of
any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under patent or other rights. Cypress products are not warranted nor intended to be used for
medical, life support, life saving, critical control or safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as
critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress products in life-support systems
application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges.
Any Source Code (software and/or firmware) is owned by Cypress Semiconductor Corporation (Cypress) and is protected by and subject to worldwide patent protection (United States and foreign),
United States copyright laws and international treaty provisions. Cypress hereby grants to licensee a personal, non-exclusive, non-transferable license to copy, use, modify, create derivative works of,
and compile the Cypress Source Code and derivative works for the sole purpose of creating custom software and or firmware in support of licensee product to be used only in conjunction with a Cypress
integrated circuit as specified in the applicable agreement. Any reproduction, modification, translation, compilation, or representation of this Source Code except as specified above is prohibited without
the express written permission of Cypress.
Disclaimer: CYPRESS MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress reserves the right to make changes without further notice to the materials described herein. Cypress does not
assume any liability arising out of the application or use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in life-support systems where
a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress’ product in a life-support systems application implies that the manufacturer
assumes all risk of such use and in doing so indemnifies Cypress against all charges.
Use may be limited by and subject to the applicable Cypress software license agreement.
Document Number: 001-50594 Rev. **
Revised January 29, 2009
Page 14 of 14
AutoStore and QuantumTrap are registered trademarks of Cypress Semiconductor Corporation. All products and company names mentioned in this document may be the trademarks of their respective
holders.
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