AN216 Differences between FM24C256 and FM24W256 Author: Harsha Medu Associated Project: No Associated Part Family: FM24C256, FM24W256 Software Version: None Related Application Notes: None AN216 discusses the key differences which need to be considered when migrating from FM24C256 to FM24W256. Table 1. Compatibility Chart Description 2 The FM24W256, a 256-Kbit serial I C wide voltage F-RAM, is a replacement device for FM24C256; FM24C256 is now obsolete. The two devices are identical in terms of pinout, package dimensions and composition, read/write functionality, Write Protect operation, and address pin functionality. This application note discusses the key differences between the two devices which need to be considered when migrating from FM24C256 to FM24W256. Is FM24W256 compatible? FM24C256 Feature or Spec Package Yes Pinout Yes Temperature Range Yes Operating Voltage Yes Operating Current Yes Drop-In Replacement or Not? Standby Current Yes From a software point of view, the two devices are identical. From a hardware point of view the key difference is the lower active and standby currents in FM24W256. Additionally, FM24W256 datasheet adds power-up and power-down ramp rate specifications of 30 µs / V and a first access time (after power-up) specification of 1 ms. Read / Write Function Yes Timing / Frequency Yes Data Retention Refer to Table 2 Endurance Yes A compatibility chart for the two devices is given in Table 1. A detailed comparison is shown in Table 2. Table 2. Detailed Comparison FM24C256 Package Types Package Outlines Pinout Temperature Range Operating Voltage Range Active Supply Current www.cypress.com -G (Wide SOIC-8) FM24W256 -EG (Wide SOIC-8) -G (SOIC-8) Comments Same, “green” wide SOIC package. The FM24W256 is also offered in “green” standard SOIC-8 package. Same outline and board footprint. Along with wide package, the FM24W256 is offered in standard SOIC-8 package. Wide SOIC-8 Wide SOIC-8, SOIC-8 - - Same –40 ºC to +85 ºC –40 ºC to +85 ºC Same 4.5 V to 5.5 V 2.7 V to 5.5 V FM24W256 has a wider operating voltage range 200 µA @ 100 kHz 100 µA @ 100 kHz 1200 µA @ 1 MHz 400 µA @ 1 MHz FM24W256 offers lower active current at all clock rates Document No. 001-86822 Rev. *A 1 Differences between FM24C256 and FM24W256 Standby Current Read / Write Function Clock Frequency Data Retention Endurance FM24C256 FM24W256 100 µA 30 µA - - 1 MHz 1 MHz 45 years (+85 ºC) Comments FM24W256 offers lower standby current Same 2-byte addressing, same Slave IDs, same device select bits Same 10 years (+85 ºC) 38 years (+75 ºC) 1E+10 1E+14 FM24W256 has better endurance VDD Power-Up Ramp Rate (tVR) - 30 µs / V Power-up ramp rate should be slower than 30 µs / V for FM24W256 VDD Power-Down Ramp Rate (tVF) - 30 µs / V Power-down ramp rate should be slower than 30 µs / V for FM24W256 Power-Up to First Access (tPU) - 1 ms After power-up, the first access of FM24W256 should be after 1 ms Critical Considerations All the parameter differences in Table 2 should be considered during the migration to FM24W256. The critical differences are discussed in this section. System designers are also recommended to review the detailed datasheets when migrating to the new part. Package Types Both the FM24C256 and the FM24W256 are offered in wide SOIC-8 packages. However there is a change in the package type. Package type -EG now represents wide SOIC-8 package and -G represents standard SOIC-8 package in FM24W256. Hence FM24W256’s -EG will be the drop in replacement for FM24C256’s -G package type. VDD Ramp Rate VDD power-up and power-down ramp rate specifications are added in FM24W256 device. Ensure that the power-up and power-down ramp rates are slower than 30 µs / V in your system. Power-Up to First Access Power-up to first access specification is added in FM24W256 device. Ensure that the FM24W256 device is accessed only after 1 ms from power-up. Conclusion AN216 discusses the differences between FM24C256 and FM24W256 which need to be considered during migration. www.cypress.com Document No. 001-86822 Rev. *A 2 Differences between FM24C256 and FM24W256 Document History Document Title: Differences between FM24C256 and FM24W256 - AN216 Document Number: 001-86822 Revision ECN Orig. of Change Submission Date Description of Change ** 3944550 GVCH 03/26/2013 New Spec. *A 4281483 MEDU 03/07/2014 Updated to Cypress Template. Added data retention spec to FM24W256 at 85 ºC. Updated "Power-up to First Access" for FM24W256 from 10 ms to 1 ms. Updated "VDD Power-down Ramp Rate" for FM24W256 from 100 µs / V to 30 µs / V. Removed VIH(max), Input / Output leakage current and Input Resistance spec from Table 2. www.cypress.com Document No. 001-86822 Rev. *A 3 Differences between FM24C256 and FM24W256 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. 001-86822 Rev. *A 4