WHITE PAPER Fan Chu, James Nicholson, Yaner Wang, Cypress Semiconductor Corp. F-RAM™, nvSRAM, and MRAM Magnetic Field Immunity Introduction Abstract This white paper compares the magnetic field immunity of three classes of nonvolatile memory: ferroelectric random-access memory (F-RAM), nonvolatile static randomaccess memory (nvSRAM), and magnetoresistive random-access memory (MRAM). Nonvolatile random-access memory (NVRAM) is memory that provides fast read and write access to any address and retains data when power is disrupted. Ferroelectric random-access memory (F-RAM™), nonvolatile static random-access memory (nvSRAM), and magnetoresistive random-access memory (MRAM) are three NVRAMs that offer faster random access times than conventional nonvolatile memories, such as flash and EEPROM. Many nonvolatile memory applications are exposed to magnetic fields; therefore, nonvolatile memory components used in these applications must be immune to the magnetic field effect to protect critical system data. Cypress conducted a lab study in which F-RAM and nvSRAM devices were exposed to magnetic fields and compared the data from the study to an Everspin MRAM datasheet to evaluate the magnetic field immunity of the three technologies. Devices 4-Mb parallel F-RAM in 44-pin TSOP II from Cypress 4-Mb parallel nvSRAM in 44-pin TSOP II from Cypress 4-Mb parallel MRAM in 44-pin TSOP II from Everspin F-RAM and nvSRAM Test Methodology Test Flow Figure 1 summarizes the procedure of each test. Write data to each sample Place the sample in the magnetic field for 1 minute Remove the sample from the magnetic field Read data from the sample Check reprogrammability Figure 1. Test Flow Chart F-RAM™, nvSRAM, and MRAM Magnetic Field Immunity 001-93328 Rev. ** August 2014 2 Cypress Semiconductor Corp. Test Setup Figure 2 shows the magnetic field setup and the two sample insertion methods—horizontal insertion and vertical insertion—of the device under test. At room temperature, nonvolatile memory samples were placed between two permanent magnets. The distance between the two magnets was adjusted to vary the magnetic field strength. Compared to horizontal insertion, vertical insertion resulted in a larger distance between the two magnets, creating a smaller magnetic field. In this setup, the maximum possible magnetic field over a horizontally oriented sample was 3,700 Gauss, while the maximum possible magnetic field over a vertically oriented sample was 2,000 Gauss. Permanent Magnet Permanent Magnet M1 Vertical Insertion Horizontal Insertion Device Under Test Device Under Test M2 Permanent Magnet Permanent Magnet Figure 2. Magnetic Field Setup and Insertion Methods Measurements A Gauss/Teslameter (Model 5070 by F.W. Bell) measured the magnetic field strength in Gauss. Table 1 shows the different units of magnetic field strength and the conversion factors between them. An ALL-100 Universal & Gang Programmer by Hi-Lo Systems wrote and read the data to and from the nvSRAM and F-RAM samples. Data written to the samples cover both data states (1 and 0) of each bit. Quantity CGS Unit* SI Unit Conversion Factor Magnetic induction (B) Gauss (G) Tesla (T) 1T = 104 G Magnetic field strength (H) Oersted (Oe) Ampere/meter (A/m) 1 A/m = 4π x 10−3 Oe *In free space, 1 Oersted = 1 Gauss. Table 1. Units for Magnetic Field Strength F-RAM™, nvSRAM, and MRAM Magnetic Field Immunity 001-93328 Rev. ** August 2014 3 Cypress Semiconductor Corp. F-RAM and nvSRAM Test Results Table 2 shows the data reliability results of F-RAM samples (FM22L16-55-TG) and nvSRAM samples (CY14B104NA-ZS45XI) using the horizontal insertion method under the test magnetic field (3,700 Gauss) during write and read. No data corruption was observed, and all the tested samples were able to be rewritten to using a different data pattern. The F-RAM and nvSRAM samples were also placed under the maximum magnetic field for 12 hours to test their performance for a longer duration. Both memory types exhibited the same results. Data Written Magnetic Field (Gauss) Magnetic Field (A/m) Sample Size Data Read Date Rewrite 0101 3,700 2.94 x 105 10 0101 Yes 3,700 2.94 x 105 10 1010 Yes 3,700 2.94 x 105 10 1111 Yes 3,700 2.94 x 105 10 0000 Yes 1010 1111 0000 Table 2. F-RAM and nvSRAM Reliability Using Horizontal Insertion Method Table 3 shows the data reliability results of F-RAM samples (FM22L16-55-TG) and nvSRAM samples (CY14B104NA-ZS45XI) using the vertical insertion method under the test magnetic field (2,000 Gauss) during write and read. No data corruption was observed, and all the tested samples were able to be rewritten to using a different data pattern. The F-RAM and nvSRAM samples were also placed under the maximum magnetic field for 12 hours to test their performance for a longer duration. Both memory types exhibited the same results. Data Written 0101 Magnetic Field (Gauss) 2,000 1010 2,000 1111 2,000 0000 2,000 Magnetic Field (A/m) 1.59 x 105 Sample Size 5 5 1.59 x 10 5 1.59 x 10 5 1.59 x 10 Data Read Data Rewrite 0101 Yes 5 1010 Yes 5 1111 Yes 5 0000 Yes Table 3. F-RAM and nvSRAM Reliability Using Vertical Insertion Method MRAM Data Table 4 shows the magnetic field immunity data from the Everspin MR2A16A datasheet. In the best case (for industrial and extended temperatures), the MRAM device (MR2A16ACYS35/ MR2A16AVYS35) is guaranteed to endure up to 125.66 Gauss (10,000 A/m) magnetic fields without data corruption and permanent device damage. Parameter Maximum magnetic field during write Maximum magnetic field during read Temp Range* Value in Gauss Value in A/m Commercial 25.13 2,000 Industrial, Extended 125.66 10,000 AEC-Q100 Grade 1 25.13 2,000 Commercial 100.53 8,000 Industrial, Extended 125.66 10,000 AEC-Q100 Grade 1 100.53 8,000 *Commercial: 0°C to +70°C, Industrial: –40°C to +85°C, Extended: –40°C to +105°C, AEC-Q 100 Grade 1: –40°C to +125°C Table 4. MRAM Reliability from Everspin Datasheet F-RAM™, nvSRAM, and MRAM Magnetic Field Immunity 001-93328 Rev. ** August 2014 4 Cypress Semiconductor Corp. Conclusion Due to its magnetic nature, the MRAM device retains data only under limited external magnetic field exposure. Data reliability is not guaranteed for applications with a magnetic field exposure exceeding 125.66 Gauss. While the MRAM (MR2A16ACYS35/MR2A16AVYS35) device is constrained by sensitivity to external magnetic fields, the Cypress F-RAM (FM22L16-55-TG) and nvSRAM (CY14B104NA-ZS45XI) devices demonstrate strong magnetic field immunity and do not show any failures under the maximum available magnetic field strengths (3,700 Gauss for the horizontal insertion and 2,000 Gauss for the vertical insertion). In addition, the F-RAM and nvSRAM devices allow rewriting with a different data pattern after exposure to the magnetic fields. In a high magnetic field environment, F-RAM and nvSRAM technologies demonstrate better magnetic field immunity than MRAM technology. Cypress Semiconductor 198 Champion Court San Jose, CA 95134-1709 Phone: 408-943-2600 Fax: 408-943-4730 http://www.cypress.com © Cypress Semiconductor Corporation, 2014. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under patent or other rights. Cypress products are not warranted nor intended to be used for medical, life support, life saving, critical control or safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, 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 products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. F-RAM is a trademark of Cypress Semiconductor Corp. All other trademarks or registered trademarks referenced herein are property of the respective corporations. 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