AN55663 Migrating from CY14E256L/STK14C88 to CY14E256LA Author: Ravi Prakash Associated Project: No Associated Part Family: CY14E256L/STK14C88 CY14E256LA Software Version: None Related Application Notes: None AN55663 provides details for migrating from the CY14E256L/STK14C88 nvSRAM parts to CY14E256LA part in applications. This application note also lists the parameter differences between the parts and the design considerations for migration when converting applications to CY14E256LA. Introduction Feature Set Cypress CY14E256LA is a 5 V, 256 Kbit (32 K x 8) nvSRAM in 0.13 micron technology. This part with a few performance enhancements is functionally equivalent to CY14E256L/STK14C88 in 0.8 micron technology but with a few differences in parameters. This application note highlights the differences between the CY14E256L/STK14C88 and the CY14E256LA and the parameters that must be considered while migrating. Note STK14C88 is the Simtek part number for CY14E256L. Overview AutoStore Enable/Disable Preventing STORE on the fly Speed STORE Cycles Data Retention CY14E256L/ STK14C88 Not Available Available 25 ns 35 ns 45 ns 1,000,000 100 years at 55 °C CY14E256LA Available Not Available 25 ns 45 ns 1,000,000 20 years at 85 °C Operating Temperature Range The following tables compare the features and parameters of the two parts. As shown in Table 1, the 256 Kbit nvSRAM is available in x8 configuration. While CY14E256L/STK14C88 is available in both commercial and industrial temperature ranges, CY14E256LA is offered only in the industrial temperature range. Table 1. Part Number Description Table 3. Operating Temperature Range Comparison Description Original Part Number Replacement Part Number 32 K x 8 CY14E256L/STK14C88 CY14E256LA Operating Temperature Range Commercial (0 to 70 °C) CY14E256L/ STK14C88 Available Industrial (–40 to 85 °C) Available CY14E256LA Not Available Available Feature Set Both the parts share the same overall feature set and are available in the operation speed bins given in Table 2. Table 2. Feature Set Comparison Feature Set AutoStore Software STORE Hardware STORE Software RECALL AutoStore Inhibit www.cypress.com CY14E256L/ STK14C88 Available Available Available Available Available CY14E256LA Available Available Available Available Not Available Packages CY14E256LA is pin compatible with CY14E256L/STK14C88 and is available in the same packages and pin configurations, and in additional packages. Table 4. Packages Comparison Package 32-pin SOIC 32-pin CDIP 44-pin TSOPII Document No. 001-55663 Rev. *F CY14E256L/ STK14C88 Available Available Not Available CY14E256LA Available Not Available Available 1 Migrating from CY14E256L/STK14C88 to CY14E256LA Parameters The CY14E256LA is a pin compatible replacement for CY14E256L/STK14C88 and will require minimum changes in the application board in most applications. However, the differences in parameters should be considered before replacing one part with the other. Table 5 lists the differences in parameters between CY14E256L/STK14C88 and CY14E256LA. Table 5. Parameter Comparison Parameter Description CY14E256L/ STK14C88 Speed CY14E256LA Min Max Min Max 25 ns - 100 - 70 35 ns - 85 - - 45 ns - 70 - 52 - - 3 - 10 Unit DC Parameters ICC1 ICC2 ICC3 ICC4 Average VCC Current Average VCC Current during STORE Average VCC Current at tRC = 200 ns, 5 V, 25 °C Average VCAP Current during AutoStore Cycle mA mA - 10 (typ) 35 (typ) - - 2 25 ns - 31 35 ns - 26 - 8 mA ISB1 Average VCC Standby Current (Standby, Cycling Input) 45 ns - 23 ISB VCC Standby Current - - 1.5 - 8 mA IIX Input Leakage Current - –5 +5 –1 +1 uA VIH Input High Voltage - 2.2 2 - V VOH Output HIGH Voltage - - - (IOUT = –2 mA) VOL Output LOW Voltage - - VCAP Storage Capacitor - 2.4 (IOUT = –4 mA) 0.4 (IOUT = 8 mA) Not specified - 54 to 260 mA 2.4 0.4 (IOUT = 4 mA) 61 to 180 V V µF AC Switching Parameters tDOE Output Enable to Data Valid 25 ns - 10 - 12 35 ns - 15 - - 45 ns - 20 - 20 ns tOHA Output Hold After Address Change - 5 - 3 - ns tLZCE Chip Enable to Output Active - 5 - 3 - ns tLZWE Output Active After End of Write - 5 - 3 - ns - - 0.55 - 20 ms - - 10 - 8 ms - - 300 - 25 ns AutoStore / Power-Up RECALL Parameters tHRECALL Power-Up RECALL Duration tSTORE STORE Cycle Duration tVSBL Low Voltage Trigger (VSWITCH) to VRESET Low Voltage Reset Level - - 3.6 VSWITCH Low Voltage Trigger Level - 4.0 4.5 - 4.4 V tDELAY Time Allowed to Complete SRAM Write Cycle - 1,000 - - 25 ns www.cypress.com low Document No. 001-55663 Rev. *F Not Applicable V 2 Migrating from CY14E256L/STK14C88 to CY14E256LA Parameter Description CY14E256L/ STK14C88 Speed Min CY14E256LA Unit Max Min Max VHDIS Output Disable Voltage - Not specified - 1.9 V tLZHSB To Output Active Time - Not specified - 5 µs tHHHD High Active Time - Not specified - 500 ns Software Controlled STORE/RECALL cycle Parameters tHA Address Hold Time - 20 - 0 - ns tRECALL RECALL Duration - - 20 - 200 µs - - 300 - 25 (tDELAY) ns - 25 ns Hardware STORE cycle Parameters tHLBL LOW to STORE Busy To Output Active Time when write latch not set tDHSB - Not specified Critical Considerations The impact of the differences in CY14E256LA with respect to the CY14E256/STK14C88 in existing applications are discussed in this section. System designers are recommended to review the detailed datasheets when migrating to the new part. DC Parameters ICC1 (Average current at full speed) is lower in CY14E256LA and hence power supply design in applications with CY14E256L/STK14C88 would require no changes when replacing the nvSRAM with the CY14E256LA in spite of the higher values in the lower speed / higher standby current. The critical parameter to consider is the VCAP. VCAP While most of the differences do not impact the application, the difference in VCAP is a critical consideration while converting from the older rev parts. VCAP is the capacitor that provides the required charge for AutoStore to complete NV store of the SRAM data during power down. The required capacitor range is different for the two parts. Table 6. VCAP Comparison Description CY14E256L/ STK14C88 CY14E256LA VCAP 54 µF to 260 µF 61 µF to 180 µF AC Switching Parameters There are a few minor differences in switching parameters between the CY14E256LA and the CY14E256L/STK14C88 as listed in the Table 5 on page 2. However, these differences do not impact most applications. For replacing 35 ns speed parts, choose the 25 ns speed parts as replacement (since 35 ns speed grade is not available in the CY14E256LA). AutoStore / Power-Up RECALL Parameters tHRECALL The power-up RECALL is much different in the CY14E256LA compared to the CY14E256L/STK14C88 because of architecture differences. Table 7. tHRECALL Comparison Description CY14E256L/ STK14C88 CY14E256LA tHRECALL 550 µs 20 ms This difference is not likely to affect applications since the initialization of the controller on the board happens at the same time. However, this should be taken into consideration when replacing the CY14E256L/STK14C88 with CY14E256LA. Therefore, any existing application which uses a capacitor value outside the overlapping range (61 µF to 180 µF) the impact of capacitor dimensions needs to be considered while changing to the new capacitor. Note The capacitor range is the absolute value of the capacitor, net of tolerence. www.cypress.com Document No. 001-55663 Rev. *F 3 Migrating from CY14E256L/STK14C88 to CY14E256LA Software Controlled STORE/RECALL Cycle Parameters Hardware STORE cycle Parameters The Software cycle parameter tRECALL is different in CY14E256LA as described below. The software address sequences are identical to that in the CY14E256L/ STK14C88 parts. The Hardware STORE parameters are improved in the CY14E256LA. The improvements are listed under the Details of Improvement section. No changes will be required in applications. tRECALL AutoStore Inhibit Software RECALL time (tRECALL) is higher in CY14E256LA. The CY14E256L/STK14C88 has the AutoStore Inhibit feature and the CY14E256LA has AutoStore Disable mode. These two provide the same result of AutoStore disable but are done by different means – hardware in CY14E256L/ STK14C88 and software in CY14E256LA. Table 8. tRECALL Comparison Description CY14E256L/ STK14C88 CY14E256LA tRECALL 20 µs 200 µs This difference could require firmware change in the existing application to increase the controller wait state when software RECALL is initiated. Software Sequence The CY14E256LA has been designed to be compatible with the CY14E256L/STK14C88 in the software sequence modes. Hence, the same Software STORE and RECALL address sequences in CY14E256L/STK14C88 works in CY14E256LA, requiring no firmware change. However, there is a difference in the required state of / during the software sequence reads as explained further. In the CY14E256L/STK14C88 while software sequence must be clocked with / controlled reads it is not necessary that / be low for the sequence to be valid. That is, it is not necessary that the read is a real read with / held LOW. But, in the CY14E256LA the software sequence may be clocked with controlled reads or controlled reads. This means that while in the CY14E256L/STK14C88 parts / state was immaterial, in the CY14E256LA parts, needs to be LOW for a valid software sequence read. It does not matter if goes LOW first or goes LOW first but the read is valid for software sequence only when both and have gone LOW. In both the CY14E256L/STK14C88 and the CY14E256LA parts must be kept HIGH for all the six read sequences. To disable AutoStore in CY14E256L/STK14C88, the power is to be connected to the VCAP pin and the VCC pin is grounded (or left open). This cannot be done in CY14E256LA. For proper operation of the device, in CY14E256LA, power is to be connected to the VCC pin only. However, AutoStore disable is more easily done through the software sequence. Therefore, if the CY14E256L/ STK14C88 is to be replaced in an application where AutoStore has been disabled, then the layout has to be modified to connect the power to the VCC pin and a software sequence has to be used to disable AutoStore function followed by a Software STORE, the first time the board is powered up. Preventing STORE In the CY14E256L/STK14C88, STORE function can be disabled on the fly by holding pin HIGH at the onset of STORE with a driver capable of sourcing 30 mA at a VOH of at least 2.2 V. This feature is not available in the 0.13 µ parts. In the CY14E256LA, a STORE initiated by any means, cannot be disabled on the fly. Data Retention The Data Retention in CY14E256LA part is improved from the older technology part. The CY14E256LA has data retention of 20 years at 85 °C against the CY14E256L/ STK14C88 data retention of 100 years at 55 °C. This would translate to over four times improvement in data retention at the same temperatures. In effect, this difference will affect applications where software sequence reads are done with / held HIGH. Firmware change will be required to take LOW when using the new part CY14E256LA. Applications where software sequence reads are performed with / LOW do not require any change. www.cypress.com Document No. 001-55663 Rev. *F 4 Migrating from CY14E256L/STK14C88 to CY14E256LA Details of Improvement Hardware STORE Related Improvements pin (Hardware STORE Busy Indication/Hardware STORE Initiation) The pin of the nvSRAM is an open drain I/O pin (internal 100 KΩ weak pull-up resistor) used to indicate or initiate a STORE operation. When a STORE operation is in progress, nvSRAM pulls the pin low to indicate that the device is busy and cannot be accessed for read/write operation. During normal operation, the pin can be pulled low to initiate a Hardware STORE operation. As shown in Table 5 on page 2, several timing parameters related to the pin input and output have changed from CY14E256L/STK14C88 to CY14E256LA. All of these changes are improvements from the original part specification and should be considered as added benefits in your system while migrating to the new part number. TDELAY If a write latch is set and the pin is pulled low, CY14E256L/STK14C88 enables 1 µs time for write operations to complete before STORE operation begins and reads and writes are inhibited. This potentially enables inadvertent data to be written to the nvSRAM during the tDELAY duration. Note rite Latch: hen a write operation is done, a ‘write latch’ is set internally. hen is pulled low, nvSRAM checks this write latch before initiating a STORE. This is done to prevent any unnecessary loss of endurance cycles. In CY14E256LA, the tDELAY parameter enables only one write cycle time for any ongoing write to complete after pin is pulled low. This improvement provides better security from inadvertent write operations. Also, if pin is pulled low externally for a minimum of tPHSB time on CY14E256LA, the output driver of pin pulls the pin low only indicating a STORE operation within 25 ns (tDELAY). This parameter for low to STORE busy is not specified in the CY14E256L/STK14C88. (See Figure 1 and Figure 2) LOW when write latch not set: If no writes are performed since the last STORE/RECALL operation, STORE operation does not start when is pulled low. However, the pin is still internally pulled low for 1 µs (tDELAY) time in the CY14E256L/ STK14C88 device. CY14E256LA device does not pull the pin low internally if write latch is not set. This improvement prevents the possibility of being in an infinite loop when pins of two nvSRAM devices are ganged. Figure 1. CY14E256L/STK14C88: AC Parameters Related to Figure 2. CY14E256LA: AC Parameters Related to Write Latch Set www.cypress.com Write Latch not Set Document No. 001-55663 Rev. *F 5 Migrating from CY14E256L/STK14C88 to CY14E256LA Power-up Recall Related Improvements Additional parameters are specified in CY14E256LA such as Output Disable Voltage (VHDIS), To Output Active Time (tLZHSB), and High Active Time (tHHHD), which helps in system design. See Figure 3 and Figure 4 for the definition of the additional specs in power-up. Also, note that remains low until the end of the power-up in the new part. This would guard against the system inadvertently thinking the part has completed the boot up prior to real completion. Figure 3. CY14E256L/STK14C88: Power-Up Recall Figure 4. CY14E256LA: Power-Up Recall www.cypress.com Document No. 001-55663 Rev. *F 6 Migrating from CY14E256L/STK14C88 to CY14E256LA Summary The application note discusses the differences between CY14E256LA in the latest 0.13 micron technology and CY14E256L/STK14C88 in the 0.8 micron technology. Several parameters related to and power-up have improved / specified in the new device enabling faster device response, greater data security, and ease of design. www.cypress.com CY14E256LA is pin compatible with and can replace the CY14E256L/STK14C88 device with minimum changes hardware/firmware in most applications. Applications where CY14E256L/STK14C88 is in AutoStore inhibit mode would require layout changes, and also, it is not possible to prevent STORE on the fly in the CY14E256LA. The value of VCAP in the existing design needs to be considered while replacing the part. Document No. 001-55663 Rev. *F 7 Migrating from CY14E256L/STK14C88 to CY14E256LA Document History Document Title: Migrating from CY14E256L/STK14C88 to CY14E256LA – AN55663 Document Number: 001-55663 Revision ECN Orig. of Change Submission Date Description of Change ** 2773126 PSR 10/01/09 New Spec. *A 3016464 PSR 09/27/10 Updated Introduction in page 1. Added a feature, Preventing STORE on the fly, to Table 2 in page 1 and added a paragraph under Critical Consideration in page 5 indicating this feature difference. Changed STORE cycles of CY14E256LA in Table 2 in page 1 to 1,000,000 and deleted the STORE cycles paragraph under Critical Consideration since the parts are identical in this. Changed ICC4 and ISB of CY14E256LA in Table 5 in page 2 to 8mA to align with datasheet spec. Updated Summary in page 7. *B 3223418 PSR 04/12/11 Added *C 3618997 PSR 06/05/12 Updated document to match with current Cypress template. hanged title from “ onverting” to “Migrating”. Reworded the Abstract for better understanding. Text updates for more clarity. No change in technical content. *D 3918276 PSR 03/01/2013 Updated Table 5 under Parameters (Changed unit of tDOE parameter from mA to ns). *E 4168635 GVCH 10/21/2013 Obsolete document. *F 4221998 GVCH 12/19/2013 Document reactivated. Updated in new template. www.cypress.com requirement differences in Software Sequence section in page 3, 4 Document No. 001-55663 Rev. *F 8 Migrating from CY14E256L/STK14C88 to CY14E256LA Worldwide Sales and Design Support ypress maintains a worldwide network of offices, solution centers, manufacturer’s representatives, and distributors. To find the office closest to you, visit us at Cypress Locations. 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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 ypress’ 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. www.cypress.com Document No. 001-55663 Rev. *F 9