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STK15C68
8K x 8 AutoStoreTM nvSRAM QuantumTrapTM CMOS Nonvolatile Static RAM
Obsolete - Not Recommend for new Deisgns
FEATURES
* Nonvolatile Storage without Battery Problems * Directly Replaces 8K x 8 Static RAM, BatteryBacked RAM or EEPROM * 25ns, 35ns and 45ns Access Times * STORE to Nonvolatile Elements Initiated by Software or AutoStoreTM on Power Down * RECALL to SRAM Initiated by Software or Power Restore * 10mA Typical ICC at 200ns Cycle Time * Unlimited READ, WRITE and RECALL Cycles * 1,000,000 STORE Cycles to Nonvolatile Elements * 100-Year Data Retention over Full Industrial Temperature Range * No Data Loss from Undershoot * Commercial and Industrial Temperatures * 28-Pin 600 or 300 mil PDIP and 350 mil SOIC Packages
DESCRIPTION
The STK15C68 is a fast SRAM with a nonvolatile element incorporated in each static memory cell. The SRAM can be read and written an unlimited number of times, while independent nonvolatile data resides in Nonvolatile Elements. Data transfers from the SRAM to the Nonvolatile Elements (the STORE operation) can take place automatically on power down using charge stored in system capacitance. Transfers from the Nonvolatile Elements to the SRAM (the RECALL operation) take place automatically on restoration of power. Initiation of STORE and RECALL cycles can also be controlled by entering control sequences on the SRAM inputs. The STK15C68 is pin-compatible with 8k x 8 SRAMs and battery-backed SRAMs, allowing direct substitution while enhancing performance. A similar device (STK16C68) with an internally integrated capacitor is available for systems with very fast slew rates. The STK12C68, which uses an external capacitor, is an alternative for these applications.
BLOCK DIAGRAM
QUANTUM TRAP 128 x 512 VCC STORE/ RECALL CONTROL
PIN CONFIGURATIONS
NC A12 A7 A6 A5 A4 A3 A2 A1 A0 DQ0 DQ1 DQ2 VSS
1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15
A5
ROW DECODER
A6 A7 A8 A9 A11 A12
DQ0 DQ1 DQ2 DQ3 DQ4 DQ5 DQ6 DQ7
STORE STATIC RAM ARRAY 128 x 512 RECALL
POWER CONTROL
SOFTWARE DETECT INPUT BUFFERS COLUMN I/O COLUMN DEC
A0 - A12
VCC W NC A8 A9 A11 G A10 E DQ7 DQ6 DQ5 DQ4 DQ3
28 - 300 PDIP 28 - 600 PDIP 28 - 350 SOIC
PIN NAMES
A0 - A12 W Address Inputs Write Enable Data In/Out Chip Enable Output Enable Power (+ 5V) Ground
A0 A1 A2 A3 A4 A10
DQ0 - DQ7
G E W
E G VCC VSS
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ABSOLUTE MAXIMUM RATINGSa
Voltage on Input Relative to Ground . . . . . . . . . . . . . .-0.5V to 7.0V Voltage on Input Relative to VSS . . . . . . . . . . -0.6V to (VCC + 0.5V) Voltage on DQ0-7 . . . . . . . . . . . . . . . . . . . . . . -0.5V to (VCC + 0.5V) Temperature under Bias . . . . . . . . . . . . . . . . . . . . . -55C to 125C Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . -65C to 150C Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1W DC Output Current (1 output at a time, 1s duration) . . . . . . . . 15mA
Note a: Stresses greater than those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only, and functional operation of the device at conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
DC CHARACTERISTICS
COMMERCIAL SYMBOL ICC1b PARAMETER MIN Average VCC Current MAX 85 75 65 3 10 2 27 23 20 1.5 1 5 2.2 VSS - .5 2.4 0.4 0 70 -40 VCC + .5 0.8 2.2 VSS - .5 2.4 0.4 85 MIN MAX 90 75 65 3 10 2 28 24 21 1.5 1 5 VCC + .5 0.8 mA mA mA mA mA mA mA mA mA mA A A V V V V C INDUSTRIAL UNITS
(VCC = 5.0V 10%)
NOTES tAVAV = 25ns tAVAV = 35ns tAVAV = 45ns All Inputs Don't Care, VCC = max W (V CC - 0.2V) All Others Cycling, CMOS Levels All Inputs Don't Care tAVAV = 25ns, E VIH tAVAV = 35ns, E VIH tAVAV = 45ns, E VIH E (V CC - 0.2V) All Others VIN 0.2V or (VCC - 0.2V) VCC = max VIN = VSS to VCC VCC = max VIN = VSS to VCC, E or G VIH All Inputs All Inputs IOUT = - 4mA IOUT = 8mA
ICC2c ICC3
b
Average VCC Current during STORE Average VCC Current at tAVAV = 200ns 5V, 25C, Typical Average VCC Current during AutoStoreTM Cycle Average VCC Current (Standby, Cycling TTL Input Levels) VCC Standby Current (Standby, Stable CMOS Input Levels) Input Leakage Current Off-State Output Leakage Current Input Logic "1" Voltage Input Logic "0" Voltage Output Logic "1" Voltage Output Logic "0" Voltage Operating Temperature
ICC4c ISB1d
ISB2d IILK IOLK VIH VIL VOH VOL TA
Note b: ICC1 and ICC3 are dependent on output loading and cycle rate. The specified values are obtained with outputs unloaded. Note c: ICC2 and ICC4 are the average currents required for the duration of the respective STORE cycles (tSTORE ) . Note d: E VIH will not produce standby current levels until any nonvolatile cycle in progress has timed out.
AC TEST CONDITIONS
Input Pulse Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to 3V Input Rise and Fall Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5ns Input and Output Timing Reference Levels . . . . . . . . . . . . . . . 1.5V Output Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Figure 1
5.0V
480 Ohms OUTPUT 255 Ohms
CAPACITANCEe
SYMBOL CIN COUT PARAMETER Input capacitance Output Capacitance
(TA = 25C, f = 1.0MHz)
MAX 8 7 UNITS pF pF CONDITIONS V = 0 to 3V V = 0 to 3V
30 pF INCLUDING SCOPE AND FIXTURE
Note e: These parameters are guaranteed but not tested.
Figure 1: AC Output Loading
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STK15C68
SRAM READ CYCLES #1 & #2
SYMBOLS NO. 1 2 3 4 5 6 7 8 9 10 11 PARAMETER #1, #2 tELQV tAVAVf tAVQV
g
(VCC = 5.0V 10%)
STK15C68-25 STK15C68-35 MIN MAX 35 35 25 10 5 5 10 0 10 0 25 0 35 0 13 0 45 5 5 13 0 15 35 15 5 5 15 45 45 20 STK15C68-45 UNITS MIN MAX 25 25 MIN MAX 45 ns ns ns ns ns ns ns ns ns ns ns
Alt. tACS tRC tAA tOE tOH tLZ tHZ tOLZ Chip Enable Access Time Read Cycle Time Address Access Time 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
tGLQV tAXQXg tELQX tEHQZh tGLQX tGHQZ
h
tOHZ tPA tPS
tELICCHe tEHICCL
d, e
Note f: W must be high during SRAM READ cycles and low during SRAM WRITE cycles. Note g: I/O state assumes E, G < VIL and W > VIH; device is continuously selected. Note h: Measured + 200mV from steady state output voltage.
SRAM READ CYCLE #1: Address Controlledf, g
tAVAV ADDRESS
5 3 2
tAVQV
DATA VALID
tAXQX DQ (DATA OUT)
SRAM READ CYCLE #2: E Controlledf
tAVAV ADDRESS tELQV E
6 tELQX 1 2
tEHICCL
7
11
tEHQZ
G tGLQV
4
tGHQZ
9
tGLQX DQ (DATA OUT)
10 tELICCH DATA VALID
8
ACTIVE
ICC
STANDBY
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STK15C68
SRAM WRITE CYCLES #1 & #2
SYMBOLS NO. #1 12 13 14 15 16 17 18 19 20 21 tAVAV tWLWH tELWH tDVWH tWHDX tAVWH tAVWL tWHAX tWLQZ
h, i
(VCC = 5.0V 10%)
STK15C68-25 PARAMETER STK15C68-35 MIN 35 25 25 12 0 25 0 0 10 5 5 13 5 MAX STK15C68-45 UNITS MIN MAX MIN 45 30 30 15 0 30 0 0 15 MAX ns ns ns ns ns ns ns ns ns ns 25 20 20 10 0 20 0 0
#2 tAVAV tWLEH tELEH tDVEH tEHDX tAVEH tAVEL tEHAX
Alt. tWC tWP tCW tDW tDH tAW tAS tWR tWZ tOW Write Cycle Time Write Pulse Width Chip Enable to End of Write Data Set-up to End of Write Data Hold after End of Write Address Set-up to End of Write Address Set-up to Start of Write Address Hold after End of Write Write Enable to Output Disable Output Active after End of Write
tWHQX
Note i: Note j:
If W is low when E goes low, the outputs remain in the high-impedance state. E or W must be VIH during address transitions.
SRAM WRITE CYCLE #1: W Controlledj
tAVAV ADDRESS tELWH E
14 19 12
tWHAX
tAVWH tAVWL W tWLWH
15 16 13 18
17
tDVWH DATA IN tWLQZ DATA OUT
PREVIOUS DATA HIGH IMPEDANCE 20 DATA VALID
tWHDX
tWHQX
21
SRAM WRITE CYCLE #2: E Controlledj
tAVAV ADDRESS tAVEL E
18 14 19 12
tELEH
tEHAX
tAVEH tWLEH W tDVEH DATA IN DATA OUT
HIGH IMPEDANCE DATA VALID 15 16 13
17
tEHDX
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STK15C68
AutoStoreTM/POWER-UP RECALL
SYMBOLS NO. Standard 22 23 24 25 26 tRESTORE tSTORE tDELAY VSWITCH VRESET Power-up RECALL Duration STORE Cycle Duration Time Allowed to Complete SRAM Cycle Low Voltage Trigger Level Low Voltage Reset Level 1 4.0 4.5 3.6 PARAMETER MIN MAX 550 10 s ms s V V e k g g
(VCC = 5.0V 10%)
STK15C68 UNITS NOTES
Note k: tRESTORE starts from the time VCC rises above VSWITCH.
AutoStoreTM/POWER-UP RECALL
VCC
5V 25 VSWITCH 26 VRESET
AutoStoreTM
23 tSTORE
POWER-UP RECALL 22 tRESTORE W DQ (DATA OUT)
24 tDELAY
POWER-UP RECALL
BROWN OUT NO STORE DUE TO NO SRAM WRITES NO RECALL (VCC DID NOT GO BELOW VRESET)
BROWN OUT AutoStoreTM NO RECALL (VCC DID NOT GO BELOW VRESET)
BROWN OUT AutoStoreTM RECALL WHEN VCC RETURNS ABOVE VSWITCH
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SOFTWARE STORE/RECALL MODE SELECTION
E W G A12 - A0 (hex) 0000 1555 0AAA 1FFF 10F0 0F0F 0000 1555 0AAA 1FFF 10F0 0F0E MODE Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM Nonvolatile STORE Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM Nonvolatile RECALL I/O with G Low Output Data Output Data Output Data Output Data Output Data Output High Z Output Data Output Data Output Data Output Data Output Data Output High Z I/O with G High Output High Z Output High Z Output High Z Output High Z Output High Z Output High Z Output High Z Output High Z Output High Z Output High Z Output High Z Output High Z NOTES
L
H
X
l
L
H
X
l
Note l:
The six consecutive addresses must be in the order listed. W must be high during all six consecutive cycles to enable a nonvolatile cycle.
SOFTWARE STORE/RECALL CYCLEm, n
STK15C68-25 NO. 27 28 29 30 31 SYMBOLS tAVAV tAVELm tELEHm tELAX
g, m
(VCC = 5.0V 10%)
STK15C68-35 MIN 35 0 25 20 20 20 MAX STK15C68-45 UNITS MIN MAX MIN 45 0 30 20 20 MAX ns ns ns ns s 25 0 20 20
PARAMETER STORE/RECALL Initiation Cycle Time Address Set-Up Time Clock Pulse Width Address Hold Time RECALL Cycle Duration
tRECALL
Note m: The software sequence is clocked with E controlled READs. Note n: The six consecutive addresses must be in the order listed in the Software STORE/RECALL Mode Selection Table: (0000, 1555, 0AAA, 1FFF, 10F0, 0F0F) for a STORE cycle or (0000, 1555, 0AAA, 1FFF, 10F0, 0F0E) for a RECALL cycle. W must be high during all six consecutive cycles.
SOFTWARE STORE/RECALL CYCLE: E Controlledn
tAVAV ADDRESS
28 ADDRESS #1 27
tAVAV
ADDRESS #6
27
tAVEL E
tELEH
29
tELAX
23 31 / tRECALL
30
tSTORE DQ (DATA OUT)
DATA VALID DATA VALID
HIGH IMPEDANCE
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DEVICE OPERATION
The STK15C68 is a versatile memory chip that provides several modes of operation. The STK15C68 can operate as a standard 8K x 8 SRAM. It has an 8K x 8 Nonvolatile Elements shadow to which the SRAM information can be copied, or from which the SRAM can be updated in nonvolatile mode.
SOFTWARE NONVOLATILE STORE
The STK15C68 software STORE cycle is initiated by executing sequential READ cycles from six specific address locations. During the STORE cycle an erase of the previous nonvolatile data is first performed, followed by a program of the nonvolatile elements. The program operation copies the SRAM data into nonvolatile memory. Once a STORE cycle is initiated, further input and output are disabled until the cycle is completed. 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 or the sequence will be aborted and no STORE or RECALL will take place. To initiate the software STORE cycle, the following READ sequence must be performed:
1. 2. 3. 4. 5. 6. Read address Read address Read address Read address Read address Read address 0000 (hex) 1555 (hex) 0AAA (hex) 1FFF (hex) 10F0 (hex) 0F0F (hex) Valid READ Valid READ Valid READ Valid READ Valid READ Initiate STORE cycle
NOISE CONSIDERATIONS
Note that the STK15C68 is a high-speed memory and so must have a high-frequency bypass capacitor of approximately 0.1F connected between VCC and VSS, using leads and traces that are as short as possible. As with all high-speed CMOS ICs, normal careful routing of power, ground and signals will help prevent noise problems.
SRAM READ
The STK15C68 performs a READ cycle whenever E and G are low and W is high. The address specified on pins A0-12 determines which of the 8,192 data bytes will be accessed. When the READ is initiated by an address transition, the outputs will be valid after a delay of tAVQV (READ cycle #1). If the READ is initiated by E or G, the outputs will be valid at tELQV or at tGLQV, whichever is later (READ cycle #2). The data outputs will repeatedly respond to address changes within the tAVQV access time without the need for transitions on any control input pins, and will remain valid until another address change or until E or G is brought high or W is brought low.
The software sequence must be clocked with E controlled READs. Once the sixth address in the sequence has been entered, the STORE cycle will commence and the chip will be disabled. It is important that READ cycles and not WRITE cycles be used in the sequence, although it is not necessary that G be low for the sequence to be valid. After the tSTORE cycle time has been fulfilled, the SRAM will again be activated for READ and WRITE operation.
SRAM WRITE
A WRITE cycle is performed whenever E and W are low. The address inputs must be stable prior to entering the WRITE cycle and must remain stable until either E or W goes high at the end of the cycle. The data on the common I/O pins DQ0-7 will be written into the memory if it is valid tDVWH before the end of a W controlled WRITE or tDVEH before the end of an E controlled WRITE. It is recommended that G be kept high during the entire WRITE cycle to avoid data bus contention on the common I/O lines. If G is left low, internal circuitry will turn off the output buffers tWLQZ after W goes low.
SOFTWARE NONVOLATILE RECALL
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 READ operations must be performed:
1. 2. 3. 4. 5. 6. Read address Read address Read address Read address Read address Read address 0000 (hex) 1555 (hex) 0AAA (hex) 1FFF (hex) 10F0 (hex) 0F0E (hex) Valid READ Valid READ Valid READ Valid READ Valid READ Initiate RECALL cycle
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Internally, RECALL is a two-step procedure. First, the SRAM data is cleared, and second, the nonvolatile information is transferred into the SRAM cells. After the tRECALL cycle time the SRAM will once again be ready for READ and WRITE operations. The RECALL operation in no way alters the data in the Nonvolatile Elements. The nonvolatile data can be recalled an unlimited number of times. If the STK15C68 is in a WRITE state at the end of power-up RECALL, the SRAM data will be corrupted. To help avoid this situation, a 10K Ohm resistor should be connected either between W and system VCC or between E and system VCC.
HARDWARE PROTECT
The STK15C68 offers hardware protection against inadvertent STORE operation and SRAM WRITEs during low-voltage conditions. When VCC < VSWITCH, software STORE operations and SRAM WRITEs are inhibited.
AutoStoreTM OPERATION
The STK15C68 uses the intrinsic system capacitance to perform an automatic store on power down. As long as the system power supply takes at least tSTORE to decay from VSWITCH down to 3.6V, the STK15C68 will safely and automatically store the SRAM data in Nonvolatile Elements on power down. In order to prevent unneeded STORE operations, automatic STORE will be ignored unless at least one WRITE operation has taken place since the most recent STORE or RECALL cycle. Softwareinitiated STORE cycles are performed regardless of whether a WRITE operation has taken place.
LOW AVERAGE ACTIVE POWER
The STK15C68 draws significantly less current when it is cycled at times longer than 50ns. Figure 2 shows the relationship between ICC and READ 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). Figure 3 shows the same relationship for WRITE cycles. If the chip enable duty cycle is less than 100%, only standby current is drawn when the chip is disabled. The overall average current drawn by the STK15C68 depends on the following items: 1) CMOS vs. TTL input levels; 2) the duty cycle of chip enable; 3) the overall cycle rate for accesses; 4) the ratio of READs to WRITEs; 5) the operating temperature; 6) the VCC level; and 7) I/O loading.
POWER-UP RECALL
During power up, or after any low-power condition (VCC < VRESET), an internal RECALL request will be latched. When VCC once again exceeds the sense voltage of VSWITCH, a RECALL cycle will automatically be initiated and will take tRESTORE to complete.
100
100
Average Active Current (mA)
80
Average Active Current (mA)
80
60
60 TTL CMOS 20
40 TTL 20 CMOS 0 50 100 150 Cycle Time (ns) 200
40
0 50 100 150 Cycle Time (ns) 200
Figure 2: ICC (max) Reads
Figure 3: ICC (max) Writes
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STK15C68 ORDERING INFORMATION
STK15C68 - P F 45 I Temperature Range
Blank = Commercial (0 to 70C) I = Industrial (-40 to 85C)
Access Time
25 = 25ns 35 = 35ns 45 = 45ns
Lead Finish
Blank = 85%Sn/15%Pb F = 100% Sn (Matte Tin)
Package
W = Plastic 28-pin 600 mil DIP P = Plastic 28-pin 300 mil DIP S = Plastic 28-pin 350 mil SOIC
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STK15C68
Document Revision History
Revision 0.0 0.1 0.2
Date December 2002 September 2003 March 2006
Summary Added lead-free lead finish Marked as Obsolete, Not recommended for new design.
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