AN308a Migrating From FM25L256B To FM25V02A Or FM25W256 Author: Girija Chougala Associated Part Family: FM25L256B, FM25V02A, and FM25W256 Related Documents: For a complete list, click here 1 AN308a discusses the key differences between FM25L256B, FM25V02A, and FM25W256 that need to be considered during migration from FM25L256B. FM25L256B is now obsolete and this application note explains how FM25V02A or FM25W256 is a replacement for FM25L256B. 1 Introduction FM25V02A and FM25W256 are the potential replacement devices for FM25L256B which is obsolete. For most designs, the FM25V02A or FM25W256 devices can be considered equivalent or better than the FM25L256B. The three devices are identical in terms of pinout, package composition and dimensions, and read/write functionality. This application note points out the differences between the FM25L256B, FM25V02A, and FM25W256 F-RAM devices. 2 Device Compatibility From a software point of view, the three devices are identical. From a hardware point of view, the key difference between the devices is the higher standby current and a change in the PCB assembly process for the DFN package. The EXPOSED PAD of the DFN package must not be soldered on the PCB in FM25V02A while FM25L256B does not have this restriction. Refer to “Critical Considerations” for more details. The FM25V02A adds many features like operation down to 2.0 V, sleep mode capability, Device ID feature, and higher speed capability. The FM25W256 offers wide voltage operation up to 5.5 V and lower standby current than the FM25V02A. Table 1 shows the compatibility chart of FM25L256B, FM25V02A and FM25W256. For a detailed comparison, see Table 3. Table 1. Compatibility Chart Potential Replacements FM25L256B Feature or Spec Is FM25V02A compatible? Is FM25W256 compatible? Package/Pinout Yes Yes Package Footprint Yes* Yes Temperature Range Yes Yes Operating Voltage Yes Yes Operating Current Yes Yes Standby Current No No Read / Write Function Yes Yes Status Register Yes Yes Timing / Frequency Yes Yes Data Retention Yes Yes Endurance Yes Yes * Packages are footprint compatible but DFN package requires change in the PCB assembly process. Refer to DFN Package Assembly Requirement for more details. www.cypress.com Document No. 001-86831 Rev. *C 1 Migrating from FM25L256B to FM25V02A or FM25W256 3 Ordering Part Numbers Table 2 gives the recommended FM25V02A and FM25W256 ordering part numbers that correspond to the FM25L256B ordering part numbers. Table 2. Recommended Ordering Part Numbers for Migration FM25L256B Ordering Part Number FM25V02A Ordering Part Number Status FM25L256B-G FM25W256 Status FM25V02A-G FM25L256B-GTR Ordering Part Number Status FM25W256-G FM25V02A-GTR Obsolete FM25W256-GTR In production In production FM25L256B-DG FM25V02A-DG Not supported FM25L256B-DGTR FM25V02A-DGTR Not supported 4 Comments Hardware change is required only for DFN package in the PCB assembly process. System firmware update is required if you wish to use the additional Device ID feature supported in FM25V02A. Comparison of FM25L256B, FM25V02A, and FM25W256 Table 3 gives a detailed comparison of the three devices. Table 3. Detailed Comparison Package Types Pinout / Package Outlines Package Footprint Temperature Range Operating Voltage Range Active Supply Current Standby Current Sleep Mode Current www.cypress.com FM25L256B FM25V02A FM25W256 Comments -G, -DG -G, -DG -G Identical “Green (RoHS)” package for SOIC and DFN. FM25W256 is not offered in DFN package. SOIC-8, DFN-8 SOIC-8, DFN-8 SOIC-8 FM25W256 is not offered in DFN package SOIC-8 SOIC-8 SOIC-8 Identical DFN-8 DFN-8 Not supported –40 ºC to +85 ºC –40 ºC to +85 ºC –40 ºC to +85 ºC 2.7 V to 3.6 V 2.0 V to 3.6 V 2.7 V to 5.5 V 500 µA @ 1 MHz 220 µA @ 1 MHz 250 µA @ 1 MHz 10.0 mA @ 20 MHz 2.5 mA @ 40 MHz 2.0 mA @ 20 MHz 10 µA 150 µA 30 µA - 8 µA Document No. 001-86831 Rev. *C - The EXPOSED PAD in FM25V02A must not be soldered on the PCB. Refer to DFN Package Assembly Requirement for more details. Identical FM25V02A allows operation down FM25W256 allows to 2.0 V, operation up to 5.5 V FM25V02A and FM25W256 offer lower active current Higher FM25V02A offers a sleep mode which can be used to reduce the standby/idle current. During wake-up from sleep mode, the device has a recovery time of 400 µs. 2 Migrating from FM25L256B to FM25V02A or FM25W256 Read / Write Function Clock Frequency Data Retention FM25L256B FM25V02A FM25W256 - - - 20 MHz 40 MHz 20 MHz 10 years (+85 ºC) 10 years (+85 ºC) 10 years (+85 ºC) 38 years (+75 ºC) 38 years (+75 ºC) 151 years (+65 ºC) 151 years (+65 ºC) Comments Identical 2-byte Identical op-codes addressing, FM25V02A offers higher speed Identical FM25V02A’s and FM25W256’s endurance is large enough to be considered as unlimited for all practical application. For a 64-byte loop, at 20 MHz, endurance is 85 years. Endurance (Write/Read Cycles) Unlimited 1E+14 1E+14 VDD Power-Up Ramp Rate (tVR) 50 µs / V 50 µs / V 30 µs / V Identical or better VDD Power-Down Ramp Rate (tVF) 50 µs / V 100 µs / V 30 µs / V Worse or better 10 ms 1 ms 1 ms Better power-up to first access specification in FM25V02A and FM25W256 ��������� pin pull-up HOLD - Internal pull-up - FM25V02A does not require any external pull-up resistor Device ID Feature - Yes - Additional feature Fast Read Op-code - Yes - Additional feature Power-Up to First Access (tPU) 5 Critical Considerations You should consider all the parameter differences mentioned in Table 3 during the migration to FM25V02A or FM25W256. This section discusses the critical differences. System designers should also review the datasheets when migrating to the new part. 5.1 Standby Current / Sleep Mode Current The FM25V02A has higher standby current of 150 µA compared to FM25L256B. But FM25V02A offers an additional sleep mode which can be used to reduce the standby/idle current. The sleep mode current is as low as 8 µA. Note that during wake-up from the sleep mode, device needs a recovery time of 400 µs. The FM25W256 has a higher standby current of 30 µA compared to FM25L256B. 5.2 New Feature: Device ID The FM25V02A incorporates a 9-byte read only Device ID (7F7F7F7F7F7FC22208h) to identify the product uniquely. The Device ID allows the host to determine the manufacturer, product density, and product revision. System firmware update is required when you wish to use this feature in FM25V02A. 5.3 DFN Package Assembly Requirement In both the FM25L256B and FM25V02A, the EXPOSED PAD of the DFN package is not connected to the die and must be left floating (in other words, no connect in the schematic design). The EXPOSED PAD in FM25V02A shown in the Figure 1 must not be soldered on the PCB. Soldering the EXPOSED PAD will cause the die to be exposed to excessive heat, which can result in bit failures and margin loss. Therefore, ensure that the EXPOSED PAD of the DFN package is masked on the PCB during the soldering process of the FM25V02A device. www.cypress.com Document No. 001-86831 Rev. *C 3 Migrating from FM25L256B to FM25V02A or FM25W256 There are two ways of masking the EXPOSED PAD, which is explained below: 1. Mask the Stencil opening for the EXPOSED PAD during stencil creation which can be done without updating the existing board layout design. 2. Mask the EXPOSED PAD in the solder paste film of the PCB design layout if you are designing a new board layout. Figure 1. 8-Pin DFN Package Outline EXPOSED PAD 6 Summary AN308a discussed the differences between FM25L256B, FM25V02A, and FM25W256 that need to be considered during migration from FM25L256B to FM25V02A or FM25W256. 7 Related Documents Datasheet FM25V02A: 256-Kbit (32 K × 8) Serial (SPI) F-RAM datasheet FM25W256: 256-Kbit (32 K × 8) Serial (SPI) F-RAM datasheet www.cypress.com Document No. 001-86831 Rev. *C 4 Migrating from FM25L256B to FM25V02A or FM25W256 Document History Document Title: AN308a - Migrating from FM25L256B to FM25V02A or FM25W256 Document Number: 001-86831 Revision ** ECN 3944550 Orig. of Change GVCH Submission Date Description of Change 03/26/2013 New Spec. 03/05/2014 Updated “VDD Power-Down Ramp Rate” for FM25L256B from “100 µs / V” to “50 µs / V”. Updated to Cypress Template. *A 4278908 MEDU Updated “Power-Up to First Access” for FM25W256 from 10 ms to 1 ms. Updated abstract. *B 4514175 GVCH 09/26/2014 Added “Ordering Part Numbers” section. Added title for Table 3. Added “Related Documents” section. Replaced FM25V02 (Not Recommended For New Design) with FM25V02A (In production) for migration. *C 4759382 GVCH 06/26/2015 Updated Device Compatibility for DFN EXPOSED PAD details. Updated Table 1 through Table 3 for DFN package compatibility. Added DFN Package Assembly Requirement. www.cypress.com Document No. 001-86831 Rev. *C 5 Migrating from FM25L256B to FM25V02A or FM25W256 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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