AN311 FM25V01 Replaces Two FM25CL64s Author: Harsha Medu Associated Project: No Associated Part Family: FM25V01, FM25CL64 Software Version: None Related Application Notes: None AN311 discusses the key differences which need to be considered when migrating from FM25CL64 to FM25V01. Description The FM25V01, a 128-Kbit SPI F-RAM, is a potential replacement for two FM25CL64 (64-Kbit) devices; FM25CL64 is now obsolete. For most designs, the FM25V01 device can be considered a superset of the FM25CL64. The two devices are identical in terms of pinout, package dimensions, and read/write functionality. This application note discusses the key differences between the two devices, apart from density, which need to be considered when migrating from FM25CL64 to FM25V01. Backward Compatible From a software point of view, the two devices are compatible. Aside from the additional address bit to access twice the memory, the two devices are read / write compatible. Both devices use the same two-byte address. Remember that the 128-Kbit device address wraps at 0x3FFF while the 64-Kbit wraps at 0x1FFF. The block protect boundaries are spaced at twice the address, compared to the 64-Kbit device. For systems that use a single FM25CL64 device, the transition to the FM25V01 could be as straightforward as changing your firmware to hold the address bit A13 LOW during SRAM read/writes. For systems that use two FM25CL64s, firmware needs to be modified to use the address bit A13 to access the full 128-Kbit memory. From a hardware point of view, the key difference between the two devices is the higher standby current. Additionally FM25V01 operates down to 2.0 V, extends the speed up to 40 MHz and adds Device ID, Sleep Mode features. It also adds power-up, power-down ramp rate and first access time (after power-up) specifications. A memory write operation is given in Figure 1 for FM25V01. Note the addition of address bit A13 in the serial address stream. This is the MSB bit for the 128-Kbit devices. A compatibility chart for the two devices is given in Table 1. A detailed comparison is shown in Table 2. Table 1. Compatibility Chart FM25CL64 Feature or Spec Is FM25V01 compatible? Package Yes Pinout Yes Temperature Range Yes Operating Voltage Yes Operating Current Yes Standby Current No Read / Write Function Yes Timing / Frequency Yes Data Retention Endurance Refer to Table 2 Yes Figure 1. FM25V01 Write Cycle (WREN not shown) www.cypress.com Document No. 001-86834 Rev. *A 1 FM25V01 Replaces Two FM25CL64s Table 2. Detailed Comparison FM25CL64 FM25V01 Comments -G, -DG -G Same “green” SOIC package. FM25V01 is not offered in “green” TDFN package. SOIC-8, TDFN-8 SOIC-8 Same outline and board footprint for SOIC. FM25V01 is not offered in “green” TDFN package. - - Same –40 ºC to +85 ºC –40 ºC to +85 ºC Same 2.7 V to 3.65 V 2.0 V to 3.6 V Package Types Package Outlines Pinout Temperature Range Operating Voltage Range 350 µA @ 1 MHz 220 µA @ 1 MHz 7 mA @ 20 MHz 2.5 mA @ 40 MHz 1 µA 150 µA Sleep Mode Current - 8 µA Read / Write Function - - 20 MHz 40 MHz Active Supply Current Standby Current Clock Frequency Data Retention 45 years (+85 ºC) FM25V01 allows operation down to 2.0 V FM25V01 offers lower active current FM25V01 has higher standby current FM25V01 offers a sleep mode which can be used to reduce the standby/idle current. During wake-up from sleep mode, the device needs a recovery time of 400 µs. Same 2-byte addressing, same op-codes FM25V01 supports higher speed 10 years (+85 ºC) 38 years (+75 ºC) Unlimited 1E+14 FM25V01’s endurance is large enough to be considered as unlimited for all practical applications. For a 64-byte loop, at 40 MHz, the FM25V01’s endurance is 43 years. VDD Power-Up Ramp Rate (tVR) - 50 µs / V Power-up ramp rate should be slower than 50 µs / V for FM25V01 VDD Power-Down Ramp Rate (tVF) - 100 µs / V Power-down ramp rate should be slower than 100 µs / V for FM25V01 Power-Up to First Access (tPU) - 250 µs After power-up, the first access of FM25V01 should be after 250 µs Endurance Critical Considerations All the parameter differences in Table 2 should be considered during the migration to FM25V01. The critical differences are discussed in this section. System designers are also recommended to review the detailed datasheets when migrating to the new part. Read / Write Function The FM25V01 device has an extra address bit, A13, to support the additional 64-Kbit memory when compared to the FM25CL64. Setting A13 to a 0 level will address the 64-Kbits of your current FM25CL64 application. Setting A13 to a 1 level will address the additional 64-Kbits of the FM25V01. Note that roll over will not happen at 0x1FFF in FM25V01; instead it will roll over at 0x3FFF. Standby Current / Sleep Mode Current The FM25V01 has higher standby current of 150 µA compared to 1 µA of FM25CL64. But FM25V01 offers an additional sleep mode feature which can be used to reduce the standby/idle current. The sleep mode current is 8 µA. Note that during wake-up from sleep mode, the device needs a recovery time of 400 µs. www.cypress.com Document No. 001-86834 Rev. *A 2 FM25V01 Replaces Two FM25CL64s VDD Ramp Rate VDD power-up and power-down ramp rate specifications are added in FM25V01 device. Ensure that the power-up ramp rate is slower than 50 µs / V and power-down ramp rate is slower than 100 µs / V in your system. Power-Up to First Access Power-up to first access specification is added in FM25V01 device. Ensure that the FM25V01 device is accessed only after 250 µs from power-up. Conclusion AN311 discusses the differences between FM25V01 and FM25CL64 which need to be considered during migration. www.cypress.com Document No. 001-86834 Rev. *A 3 FM25V01 Replaces Two FM25CL64s Document History Document Title: FM25V01 Replaces Two FM25CL64s - AN311 Document Number: 001-86834 Revision ECN Orig. of Change Submission Date Description of Change ** 3944550 GVCH 03/26/2013 New Spec. *A 4281267 MEDU 03/07/2014 Updated to Cypress Template. Added Compatibility Table and Detailed Comparison Table. www.cypress.com Document No. 001-86834 Rev. *A 4 FM25V01 Replaces Two FM25CL64s Worldwide Sales and Design Support Cypress 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 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. www.cypress.com Document No. 001-86834 Rev. *A 5