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STK25CA8
128K x 8 AutoStoreTM nvSRAM QuantumTrapTM CMOS Nonvolatile Static RAM Module
FEATURES
* Nonvolatile Storage without Battery Problems * Directly Replaces 128K x 8 Static RAM, BatteryBacked RAM or EEPROM * 35ns and 45ns Access Times * STORE to EEPROM Initiated by AutoStoreTM on Power Down * RECALL to SRAM on Power Restore * 22mA ICC at 200ns Cycle Time * Unlimited READ, WRITE and RECALL Cycles * 1,000,000 STORE Cycles to EEPROM * 100-Year Data Retention Over Full Commercial Temperature Range * Commercial and Industrial Temperatures * 32-Pin 600 mil Dual In-Line Module
DESCRIPTION
The Simtek STK25CA8 is a fast static RAM with a nonvolatile, electrically erasable PROM 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 the EEPROM. Data transfers from the SRAM to the EEPROM (the STORE operation) can take place automatically on power down using charge stored in system capacitance. Transfers from the EEPROM to the SRAM (the RECALL operation) take place automatically on restoration of power.
BLOCK DIAGRAM
A15 A16 A5 A6 A7 A8 A9 A11 A12 A13 A14
DQ0 DQ1 DQ2 DQ3 DQ4 DQ5 DQ6 DQ7 MODULE DECODER EEPROM ARRAY 512 x 512 STORE STATIC RAM ARRAY 512 x 512 RECALL
PIN CONFIGURATIONS
NC A16 A14 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 15 16 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17
VCC STORE/ RECALL CONTROL
POWER CONTROL
VCC A15 NC W A13 A8 A9 A11 G A10 E DQ7 DQ6 DQ5 DQ4 DQ3
ROW DECODER
32 - 600 mil Dual In-Line Module
PIN NAMES
INPUT BUFFERS COLUMN I/O COLUMN DEC
A0 - A16 W DQ0 - DQ7 Address Inputs Write Enable Data In/Out Chip Enable Output Enable Power (+ 5V) Ground
A0 A1 A2 A3 A4 A10
E
G E W
G VCC VSS
August 1999
6-1
STK25CA8
ABSOLUTE MAXIMUM RATINGSa
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 ICC1
b
(VCC = 5.0V 10%)
INDUSTRIAL UNITS MIN MAX 140 125 20 22 18 9 2 10 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 150 133 25 25 20 9 2 10 VCC + .5 0.8 mA mA mA mA mA mA A A V V V V C tAVAV = 35ns tAVAV = 45ns All Inputs Don't Care, VCC = max W (VCC - 0.2V) All Others Cycling, CMOS Levels All Inputs Don't Care E (VCC - 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 NOTES
PARAMETER Average VCC Current Average VCC Current During STORE Average VCC Current at tAVAV = 200ns Average VCC Current During AutoStoreTM Cycle 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
ICC2c ICC3b ICC4 ISBd IILK IOLK VIH VIL VOH VOL TA
c
Note b: ICC1 and ICC3 are dependent on output loading and cycle rate. The specified values are obtained with outputs unloaded. Note c: ICC and ICC are the average currents required for the duration of the respective STORE cycles (tSTORE ) . 2 4 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 20 28 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
August 1999
6-2
STK25CA8
SRAM READ CYCLES #1 & #2
SYMBOLS NO. 1 2 3 4 5 6 7 8 9 10 11 PARAMETER #1, #2 tELQV tAVAVf tAVQVg tGLQV tAXQXg tELQX tEHQZh tGLQX tGHQZh tELICCHe tEHICCLd, e Alt. tACS tRC tAA tOE tOH tLZ tHZ tOLZ tOHZ tPA tPS 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 0 35 0 13 0 45 5 5 13 0 15 35 35 15 5 5 15 MIN MAX 35 45 45 20 MIN MAX 45 ns ns ns ns ns ns ns ns ns ns ns
(VCC = 5.0V 10%)
STK25CA8-35 STK25CA8-45 UNITS
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
1 1
tEHQZ
G
8 tGLQX
tGLQV
4
tGHQZ
9
DQ (DATA OUT)
10 tELICCH ACTIVE
DATA VALID
ICC
STANDBY
August 1999
6-3
STK25CA8
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 tWLQZh, i tWHQX #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 5 PARAMETER MIN 35 25 25 12 0 25 0 0 13 5 MAX MIN 45 30 30 15 0 30 0 0 15 MAX ns ns ns ns ns ns ns ns ns ns
(VCC = 5.0V 10%)
STK25CA8-35 STK25CA8-45 UNITS
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 1 9 12
tWHAX
tAVWH
18 tAVWL 13
17
W
tWLWH
15 16
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 12
tELEH
tEHAX
19
tAVEH tWLEH W tDVEH DATA IN DATA OUT
HIGH IMPEDANCE DATA VALID 15 13
17
tEHDX
16
August 1999
6-4
STK25CA8
AutoStoreTM/POWER-UP RECALL
SYMBOLS NO. Standard 22 23 24 25 26 tRESTORE tSTORE tDELAY VSWITCH VRESET Power-up RECALL Duration PARAMETER MIN MAX 550 10 1 4.0 4.5 3.9 s ms s V V k g g
(VCC = 5.0V 10%)
STK25CA8 UNITS NOTES
STORE Cycle Duration
Time Allowed to Complete SRAM Cycle Low Voltage Trigger Level Low Voltage Reset Level
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
August 1999
6-5
STK25CA8
DEVICE OPERATION
The STK25CA8 is a versatile memory module that provides two modes of operation. The STK25CA8 can operate as a standard 128K x 8 SRAM. It has a 128K x 8 EEPROM shadow to which the SRAM information can be copied, or from which the SRAM can be updated in nonvolatile mode.
AutoStoreTM OPERATION
The STK25CA8 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 STK25CA8 will safely and automatically store the SRAM data in EEPROM on power down. In order to prevent unneeded STORE operations, automatic STOREs will be ignored unless at least one WRITE operation has taken place since the most recent STORE or RECALL cycle.
NOISE CONSIDERATIONS
Note that the STK25CA8 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.
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. If the STK25CA8 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.
SRAM READ
The STK25CA8 performs a READ cycle whenever E and G are low and W is high. The address specified on pins A0-16 determines which of the 131,072 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.
HARDWARE PROTECT
The STK25CA8 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.
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.
LOW AVERAGE ACTIVE POWER
The STK25CA8 draws significantly less current when it is cycled at times longer than 50ns. 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 STK25CA8 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.
August 1999
6-6
STK25CA8 ORDERING INFORMATION
STK25CA8 - D 45 I Temperature Range
Blank = Commercial (0 to 70C) I = Industrial (-40 to 85C)
Access Time
35 = 35ns 45 = 45ns
Package
D = 32-pin 600 mil Dual In-Line Module
August 1999
6-7

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