CY14B256L-SZ45XIT

CY14B256L 256 Kbit (32K x 8) nvSRAM Features ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Functional Description The Cypress CY14B256L is a fast static RAM with a nonvolatile element in each memory cell. The embedded 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. A hardware STORE is initiated with the HSB pin. 25 ns, 35 ns, and 45 ns access times Pin compatible with STK14D88 Hands off automatic STORE on power down with only a small capacitor STORE to QuantumTrap™ nonvolatile elements is initiated by software, hardware, or AutoStore™ on power down RECALL to SRAM initiated by software or power up Unlimited READ, WRITE, and RECALL cycles 200,000 STORE cycles to QuantumTrap 20 year data retention at 55°C Single 3V +20%, –10% operation Commercial and industrial temperature 32-pin (300 mil) SOIC and 48-pin (300 mil) SSOP packages RoHS compliance Logic Block Diagram Quantum Trap 512 X 512 A5 A6 A7 A8 A9 A 11 A 12 A 13 A 14 V CC V CAP STORE POWER CONTROL STORE/ RECALL CONTROL ROW DECODER STATIC RAM ARRAY 512 X 512 RECALL HSB SOFTWARE DETECT COLUMN I/O A13 - A 0 DQ 0 DQ 2 DQ 3 DQ 4 DQ 5 DQ 6 DQ 7 INPUT BUFFERS DQ 1 COLUMN DEC A 0 A 1 A 2 A 3 A 4 A 10 OE CE WE Cypress Semiconductor Corporation Document Number: 001-06422 Rev. *H • 198 Champion Court • San Jose, CA 95134-1709 • 408-943-2600 Revised January 30, 2009 [+] Feedback CY14B256L Pin Configurations Figure 1. Pin Diagram - 32-Pin SOIC and 48-Pin SSOP Pin Definitions Pin Name A0–A14 DQ0-DQ7 WE CE OE VSS VCC HSB W E G Alt IO Type Input Input Input Input Ground Description Address Inputs. Used to select one of the 32,768 bytes of the nvSRAM. Write Enable Input, Active LOW. When the chip is enabled and WE is LOW, data on the IO pins is written to the specific address location. Chip Enable Input, Active LOW. When LOW, selects the chip. When HIGH, deselects the chip. Output Enable, Active LOW. The active LOW OE input enables the data output buffers during read cycles. Deasserting OE HIGH causes the IO pins to tri-state. Ground for the Device. The device is connected to ground of the system. Input or Output Bidirectional Data IO Lines. Used as input or output lines depending on operation. Power Supply Power Supply Inputs to the Device. Input or Output Hardware Store Busy (HSB). When LOW, this output indicates a Hardware Store is in progress. When pulled low external to the chip, it initiates a nonvolatile STORE operation. A weak internal pull up resistor keeps this pin high if not connected (connection optional). Power Supply AutoStore Capacitor. Supplies power to nvSRAM during power loss to store data from SRAM to nonvolatile elements. No Connect No Connect. This pin is not connected to the die. VCAP NC Document Number: 001-06422 Rev. *H Page 2 of 18 [+] Feedback CY14B256L Device Operation The CY14B256L nvSRAM is made up of two functional components paired in the same physical cell. These are an SRAM memory cell and a nonvolatile QuantumTrap cell. The SRAM memory cell operates as a standard fast static RAM. Data in the SRAM is transferred to the nonvolatile cell (the STORE operation) or from the nonvolatile cell to SRAM (the RECALL operation). This unique architecture enables the storage and recall of all cells in parallel. During the STORE and RECALL operations, SRAM READ and WRITE operations are inhibited. The CY14B256L supports unlimited reads and writes similar to a typical SRAM. In addition, it provides unlimited RECALL operations from the nonvolatile cells and up to 200K STORE operations. the VCAP pin is driven to 5V by a charge pump internal to the chip. A pull up is placed on WE to hold it inactive during power up. Figure 2. AutoStore Mode V CC V CAP V CAP V CC 10k Ohm WE SRAM Read The CY14B256L performs a READ cycle whenever CE and OE are LOW while WE and HSB are 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 transitions on any control input pins, and remains valid until another address change or until CE or OE is brought HIGH, or WE or HSB is brought LOW. SRAM Write A WRITE cycle is performed whenever CE and WE are LOW and HSB is HIGH. 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. To reduce unnecessary nonvolatile stores, AutoStore and Hardware Store operations 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 a WRITE operation has taken place. An optional pull-up resistor is shown connected to HSB. The HSB signal is monitored by the system to detect if an AutoStore cycle is in progress. Hardware STORE (HSB) Operation The CY14B256L provides the HSB pin for controlling and acknowledging the STORE operations. The HSB pin is used to request a hardware STORE cycle. When the HSB pin is driven LOW, the CY14B256L conditionally initiates a STORE operation after tDELAY. An actual STORE cycle only begins if a WRITE to the SRAM takes place since the last STORE or RECALL cycle. The HSB pin also acts as an open drain driver that is internally driven LOW to indicate a busy condition, while the STORE (initiated by any means) is in progress. SRAM READ and WRITE operations, that are in progress when HSB is driven LOW by any means, are given time to complete before the STORE operation is initiated. After HSB goes LOW, the CY14B256L continues SRAM operations for tDELAY. During tDELAY, multiple SRAM READ operations take place. If a WRITE is in progress when HSB is pulled LOW, it allows a time, tDELAY to complete. However, any SRAM WRITE cycles requested after HSB goes LOW are inhibited until HSB returns HIGH. If HSB is not used, it is left unconnected. AutoStore Operation The CY14B256L stores data to nvSRAM using one of three storage operations: 1. Hardware store activated by HSB 2. Software store activated by an address sequence 3. AutoStore on device power down AutoStore operation is a unique feature of QuantumTrap technology and is enabled by default on the CY14B256L. During normal operation, the device draws current from VCC to charge a capacitor connected to the VCAP pin. This stored charge is used by the chip to perform a single STORE operation. If the voltage on the VCC pin drops below VSWITCH, the part automatically disconnects the VCAP pin from VCC. A STORE operation is initiated with power provided by the VCAP capacitor. Figure 2 shows the proper connection of the storage capacitor (VCAP) for automatic store operation. Refer to the DC Electrical Characteristics on page 7 for the size of VCAP. The voltage on Document Number: 001-06422 Rev. *H Hardware RECALL (Power Up) During power up or after any low power condition (VCC < VSWITCH), an internal RECALL request is latched. When VCC Page 3 of 18 0.1UF [+] Feedback CY14B256L once again exceeds the sense voltage of VSWITCH, a RECALL cycle is automatically initiated and takes tHRECALL to complete. Data Protection The CY14B256L protects data from corruption during low voltage conditions by inhibiting all externally initiated STORE and WRITE operations. The low voltage condition is detected when VCC is less than VSWITCH. If the CY14B256L is in a WRITE mode (both CE and WE are low) at power up after a RECALL or after a STORE, the WRITE is inhibited until a negative transition on CE or WE is detected. This protects against inadvertent writes during power up or brown out conditions. Software STORE Data is transferred from the SRAM to the nonvolatile memory by a software address sequence. The CY14B256L 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. 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: 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 The software sequence is clocked with CE controlled READs or OE 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. Noise Considerations The CY14B256L 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 reduce circuit noise. Low Average Active Power CMOS technology provides the CY14B256L the benefit of drawing significantly less current when it is cycled at times longer than 50 ns. Figure 3 shows the 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 = 3.6V, 100% duty cycle on chip enable). Only standby current is drawn when the chip is disabled. The overall average current drawn by the CY14B256L depends on the following items: ■ ■ ■ ■ ■ The duty cycle of chip enable The overall cycle rate for accesses The ratio of READs to WRITEs CMOS versus TTL input levels The operating temperature The VCC level IO loading 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: 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 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. ■ ■ Figure 3. Current vs. Cycle Time Document Number: 001-06422 Rev. *H Page 4 of 18 [+] Feedback CY14B256L Preventing Store Disable the AutoStore function by initiating an AutoStore Disable sequence. A sequence of READ operations is performed in a manner similar to the software STORE initiation. To initiate the AutoStore Disable sequence, perform the following sequence of CE controlled or OE controlled READ operations: 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 0x03F8 AutoStore Disable Re-enable the AutoStore by initiating an AutoStore Enable sequence. A sequence of READ operations is performed in a manner similar to the software RECALL initiation. To initiate the AutoStore Enable sequence, perform the following sequence of CE controlled or OE controlled READ operations: 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 0x07F0 AutoStore Enable If the AutoStore function is disabled or re-enabled, a manual STORE operation (Hardware or Software) is issued to save the AutoStore state through subsequent power down cycles. The part comes from the factory with AutoStore enabled. ■ 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 applications has resulted in the following suggestions as best practices: ■ 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 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 an NV array is in a set programmed state. Routines that check memory content values to determine first time system configuration, cold or warm boot status, and so on 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. Power up boot firmware routines should rewrite the nvSRAM into the desired state. While the nvSRAM is shipped in a preset state, the 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, incoming inspection routines, and so on). If autostore is firmware disabled, it does not reset to “autostore enabled” on every power down event captured by the nvSRAM. The application firmware should re-enable or re-disable autostore on each reset sequence based on the behavior desired. The VCAP value specified in this data sheet includes a minimum and a maximum value size. Best practice is to meet this requirement and not exceed the maximum VCAP value because higher inrush currents may reduce the reliability of the internal pass transistor. Customers that want to use a larger VCAP value to make sure there is extra store charge should discuss their VCAP size selection with Cypress to understand any impact on the VCAP voltage level at the end of a tRECALL period. ■ ■ Document Number: 001-06422 Rev. *H Page 5 of 18 [+] Feedback CY14B256L Table 1. Hardware Mode Selection CE H L L L WE X H L H OE X L X L A14 – A0 X X X 0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x03F8 0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x07F0 0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x0FC0 0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x0C63 Mode Not Selected Read SRAM Write SRAM Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM AutoStore Disable Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM AutoStore Enable Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM Nonvolatile Store Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM Nonvolatile Recall IO Output High Z Output Data Input Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data 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 Power Standby Active Active Active[1, 2, 3] L H L Active[1, 2, 3] L H L Active ICC2[1, 2, 3] L H L Active[1, 2, 3] Notes 1. The six consecutive address locations are in the order listed. WE is HIGH during all six cycles to enable a nonvolatile cycle. 2. While there are 15 address lines on the CY14B256L, only the lower 14 lines are used to control software modes. 3. IO state depends on the state of OE. The IO table shown is based on OE Low. Document Number: 001-06422 Rev. *H Page 6 of 18 [+] Feedback CY14B256L 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 Ambient Temperature with Power Applied ............................................ –55°C to +125°C Supply Voltage on VCC Relative to GND ..........–0.5V to 4.1V Voltage Applied to Outputs in High Z State ....................................... –0.5V to VCC + 0.5V Input Voltage...........................................–0.5V to Vcc + 0.5V Transient Voltage ( 2001V (MIL-STD-883, Method 3015) Latch Up Current ................................................... > 200 mA Operating Range Range Commercial Industrial Ambient Temperature 0°C to +70°C -40°C to +85°C VCC 2.7V to 3.6V 2.7V to 3.6V DC Electrical Characteristics Parameter ICC1 Description Average VCC Current Over the operating range (VCC = 2.7V to 3.6V) [4] Test Conditions tRC = 25 ns tRC = 35 ns tRC = 45 ns Dependent on output loading and cycle rate. Values obtained without output loads. IOUT = 0 mA. All Inputs Do Not Care, VCC = Max Average current for duration tSTORE Commercial Min Max 65 55 50 70 60 55 3 10 Unit mA mA mA mA mA mA mA Industrial ICC2 ICC3 Average VCC Current during STORE 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 without output loads. Typical Average VCAP Current All Inputs Do Not Care, VCC = Max during AutoStore Cycle Average current for duration tSTORE VCC Standby Current CE > (VCC – 0.2V). All others VIN < 0.2V or > (VCC – 0.2V). Standby current level after nonvolatile cycle is complete. Inputs are static. f = 0 MHz. VCC = Max, VSS < VIN < VCC VCC = Max, VSS < VIN < VCC, CE or OE > VIH or WE < VIL -1 -1 2.0 VSS – 0.5 IOUT = –2 mA IOUT = 4 mA Between VCAP pin and Vss, 6V rated. 17 2.4 ICC4 ISB 3 3 mA mA IIX IOZ VIH VIL VOH VOL VCAP Input Leakage Current Off State Output Leakage Current Input HIGH Voltage Input LOW Voltage Output HIGH Voltage Output LOW Voltage Storage Capacitor +1 +1 VCC + 0.5 0.8 0.4 120 μA μA V V V V uF Data Retention and Endurance Parameter DATAR NVC Data Retention at 55°C Nonvolatile STORE Operations Description Min 20 200 Unit Years K Note 4. The HSB pin has IOUT = –10 μA for VOH of 2.4 V. This parameter is characterized but not tested. Document Number: 001-06422 Rev. *H Page 7 of 18 [+] Feedback CY14B256L Capacitance Parameter CIN COUT In the following table, the capacitance parameters are listed.[5] Description Input Capacitance Output Capacitance Test Conditions TA = 25°C, f = 1 MHz, VCC = 0 to 3.0V Max 7 7 Unit pF pF Thermal Resistance Parameter In the following table, the thermal resistance parameters are listed.[5] Description Thermal Resistance (Junction to Ambient) Thermal Resistance (Junction to Case) Test Conditions Test conditions follow standard test methods and procedures for measuring thermal impedance, per EIA / JESD51. 32-SOIC 42.36 21.41 48-SSOP 44.26 25.56 Unit °C/W °C/W ΘJA ΘJC Figure 4. AC Test Loads R1 577Ω 3.0V Output 30 pF R2 789Ω Output 5 pF R2 789Ω 3.0V R1 577Ω For Tri-state Specs AC Test Conditions Input Pulse Levels .................................................... 0V to 3V Input Rise and Fall Times (10% - 90%)........................