AN215 Migrating from FM24C64 to FM24C64B Author: Girija Chougala Associated Project: No Associated Part Family: FM24C64, FM24C64B Software Version: None Related Documents: For a complete list, click here AN215 discusses the key differences that need to be considered when migrating from FM24C64 to FM24C64B. A compatibility chart for the two devices is given in Table 1. For a detailed comparison, see Table 3. Introduction 2 FM24C64B, a 64-Kbit I C F-RAM™, is a replacement device for FM24C64, which is now obsolete. The two devices are identical in terms of pinout, package composition and dimensions, read/write functionality, and address pin functionality. This application note discusses the key differences between the two devices that need to be considered when migrating from FM24C64 to FM24C64B. Drop-In Replacement or Not? From a software point of view, the two devices are identical except for the write protect (WP) function. Customers that used the WP pin on the FM24C64 should carefully read the Write Protect Feature section. From a hardware point of view, the key difference between the devices is the lower active current in FM24C64B. Additionally, the FM24C64B datasheet adds a power-up and power-down ramp rate specification of 30 µs/V and a power-up to first access specification of 10 ms. Table 1. Compatibility Chart FM24C64 Feature or Spec Is FM24C64B compatible? Package Yes Pinout Yes Temperature Range Yes Operating Voltage Yes Operating Current Yes Standby Current Yes Read/Write Function Yes Write Protect Feature Refer to Table 3 Timing/Frequency Yes Data Retention Refer to Table 3 Endurance Yes Ordering Part Numbers Table 2 provides the recommended FM24C64B ordering part numbers that correspond to the now obsolete FM24C64 ordering part numbers. Table 2. Recommended Ordering Part Numbers for Migration Obsolete Ordering Part Number (FM24C64) FM24C64-G FM24C64-GTR www.cypress.com Recommended Ordering Part Number (FM24C64B) Comments FM24C64B-G No hardware change. FM24C64B-GTR System firmware change is required if write protect feature is used in the current application (refer to the Write Protect Feature section for details). Document No. 001-86830 Rev. *B 1 Migrating from FM24C64 to FM24C64B Comparison of FM24C64 and FM24C64B From the hardware and software point of view, FM24C64B is a superset of FM24C64. FM24C64B has improved DC specifications compared to FM24C64. Table 3 gives a detailed comparison of the two devices. Table 3. Detailed Comparison Parameter FM24C64 FM24C64B -G -G SOIC-8 SOIC-8 – – Same –40 ºC to +85 ºC –40 ºC to +85 ºC Same 4.5 V to 5.5 V 4.5 V to 5.5 V Same 150 µA @ 100 kHz 100 µA @ 100 kHz 1200 µA @ 1 MHz 400 µA @ 1 MHz 10 µA 10 µA Read/Write Function – – Same 2-byte addressing, slave IDs, device select bits Write Protect Feature Upper quadrant of memory Full memory Different. FM24C64B protects full memory compared to the upper quadrant (upper one-fourth) of the memory in FM24C64. 1 MHz 1 MHz Package Type Package Outline Pinout Temperature Range Operating Voltage Range Active Supply Current Standby Current Clock Frequency Comments Same “green” SOIC package Same outline and board footprint FM24C64B offers lower active current at all clock rates. Same Same 10 years (+85 ºC) Data Retention 45 years (+85 ºC) 38 years (+75 ºC) Data retention is lower. 151 years (+65 ºC) Endurance 1E + 12 1E + 14 FM24C64B has better endurance. VDD Power-Up Ramp Rate (tVR) – 30 µs/V Power-up ramp rate should be slower than 30 µs/V for FM24C64B. VDD Power-Down Ramp Rate (tVF) – 30 µs/V Power-down ramp rate should be slower than 30 µs/V for FM24C64B. Power-Up to First Access (tPU) – 10 ms After power-up, the first access of FM24C64B should be after 10 ms. Critical Considerations You should consider all the parameter differences mentioned in Table 3 during the migration to FM24C64B. This section discusses the critical differences. System designers should also review the datasheet when migrating to the new part. Write Protect Feature When the WP (Write Protect) input pin is held HIGH (WP = 1), the FM24C64B protects the full memory, whereas the FM24C64 protects only the upper quadrant (one-fourth of memory: address 1800h to 1FFFh). If the write protect function was used on the FM24C64 such that writes to the unprotected address quadrants were made while WP = 1, then you will need to make system firmware changes to accommodate this change. VDD Ramp Rate VDD power-up and power-down ramp rate specifications are added in the FM24C64B device. Ensure that the power-up and power-down ramp rates are slower than 30 µs/V in your system. www.cypress.com Document No. 001-86830 Rev. *B 2 Migrating from FM24C64 to FM24C64B Power-Up to First Access The power-up to first access specification is added in the FM24C64B device. Ensure that the FM24C64B device is accessed only after 10 ms from power-up. Summary AN215 discussed the differences between FM24C64 and FM24C64B that need to be considered during migration to the FM24C64B device. Related Documents Datasheet FM24C64B: 64-Kbit (8 K × 8) Serial (I C) F-RAM datasheet 2 Application Note AN304 – SPI GUIDE FOR F-RAM www.cypress.com Document No. 001-86830 Rev. *B 3 Migrating from FM24C64 to FM24C64B Document History Document Title: Migrating from FM24C64 to FM24C64B - AN215 Document Number: 001-86830 Revision ECN Orig. of Change Submission Date Description of Change ** 3944550 GVCH 03/26/2013 New Spec. *A 4278231 MEDU 02/11/2014 Updated to Cypress Template. Updated “Active Supply Current” for FM24C64 from “1000 µA @ 1 MHz” to “1200 µA @ 1 MHz.” Added data retention specification to FM24C64B at 85 ºC. Updated endurance for FM24C64B from 1E+12 to 1E+14. Updated "VDD Power-Down Ramp Rate" for FM24C64B from 100 µs / V to 30 µs / V. Removed VIH (max) specification from Table 2. *B 4462206 GVCH 07/31/2014 Changed title from “Differences between FM24C64 and FM24C64B” to “Migrating from FM24C64 to FM24C64B.” Added “Write Protect Feature” details. Added “Ordering Part Numbers” section. Added title and description for Table 3. Added “Related Documents” section. www.cypress.com Document No. 001-86830 Rev. *B 4 Migrating from FM24C64 to FM24C64B 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. 001-86830 Rev. *B 5