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
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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
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August 2014
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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
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August 2014
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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
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F-RAM™, nvSRAM, and MRAM
Magnetic Field Immunity
001-93328 Rev. **
August 2014