MR25Hxxx Byte Write Cycle
What happens if CS# is brought high in the middle of a BYTE WRITE CYCLE (prior to an integral multiple of 8 clocks)?
The truncated last byte is not written to memory.
INVALID OP CODE COMMANDS
What happens when an invalid Op Code is entered for a Serial SPI device?
The invalid code will be ignored by the device.
Is Everspin developing process/technology solutions to increase the immunity to magnetic fields?
Everspin MRAM standard product magnetic shielding provides excellent immunity to magnetic influence in all general applications. Everspin will always be looking for ways to increase immunity to external magnetic fields and changes will be announced whenever we have developed a qualified product with increased immunity. Specific immunity specifications for any product are available in the product data sheet.
How sensitive is an MRAM to bit errors induced by external magnetic fields?
All Everspin MRAM devices are built into packages with integrated magnetic shields that provide significant protection from locally strong magnetic fields. Each MRAM product is qualified and rated to be immune to magnetic fields up to a specified maximum. The absolute maximum rating for exposure to external magnetic fields is different for each MRAM and is given in each product datasheet.
MAGNETIC IMMUNITY, EFFECT ON MRAM OF MAGNETIC FIELD
How is MRAM affected by external magnetic fields?
The maximum extermal magnetic field tolerable by Everspin MRAM without effect depends on the device operating state. We specify two different absolute maximum field specifications for maximum tolerable extermal magnetic fields. Hmax_write, is the maximum extermal magnetic field tolerable during data programming. Hmax_read is the maximum extermal magnetic field tolerable during read operations, standby mode or unpowered (no write) operations. Specific values for these parameters are given in the data sheets for all Everspin MRAM devices.
MAGNETIC FIELD IMMUNITY STANDARDS
Is there an accepted standard for maximum allowed magnetic fields for all integrated circuits?
Yes. The International Electrotechnical Commission IEC 61000-4-8: Electromagnetic compatibility (EMC) - Part 4-8: Power frequency magnetic field immunity test. This relates to the immunity requirements of equipment to magnetic disturbances at power frequency. The maximum specification for continuous fields is 100 A/m (1.3 Oe) and for pulsed field 1000 A/m (13 Oe), both much lower than the MRAM absolute maximum field spec during write of 2000 A/m (25 Oe).
USE OF MAGNETIC TOOLS AROUND MRAM
Can I use magnetized tools near MRAM?
Typical magnetized tools, such as screwdrivers with magnetically attached bits, can be used safely around unpowered MRAM without any negative effect, provided the tool is kept at least one millimeter away from the MRAM device. Care should be taken to avoid direct contact with the MRAM package. As with any electronic component, it is not advisable to use tools in close proximity to actively powered circuits.
MAGNETIC FIELD, DISK DRIVE
How does the magnetic field spec for MRAM compare with that for Hard Disk Drives?
Everspin MRAMs have absolute maximum magnetic field specifications comparable to Hard Disk drives.
MRAM MAGNETIC FIELD
I have heard that the magnetic fields generated by MRAM can cause issues. Is this a real source for concern? If so, what steps are recommended to avoid problems?
The magnetic fields generated by the MRAM device are very small and localized. In addition Everspin MRAM devices are shielded with a soft magnetic material that contains any flux generated from within the device. You shouldn't need to take any precautions in regards to shielding other devices from MRAM magnetic fields.
MRAM MAGNETIC FIELD, MEASUREMENT UNITS
What is the relationship of the magnetic field units Oe and A/m?
The unit of magnetic field Oersted (Oe) is from the CGS unit system. In the SI unit system the unit of magnetic field is Ampere/meter (A/m). The conversion between is 1 Oe = 79.6 A/m.
What are your standard ESD testing requirements?
Our standard ESD requirements are: Human Body Model: 2kV, Charged Device Model: 500V, Machine: not usually tested.
What is the leadframe material?
Cu Alloy 194. For more details request our Materials Composition Declaration document.
What is the moisture sensitivity level of an MRAM part?
MSL-3 is the standard for all Everspin MRAM products. Some device/package combinations may be rated for less time out of the bag when in the early stages of their release and full MSL-3 qualification has not completed. Please check the device data sheet or contact Everspin to confirm the MSL level for a specific device.
PART MARKING, DATE CODE
Everspin has used 2 types of the marking in the past. Is there any chance to have "FATWLYYWW" type of marking from now on?
We are using the alternative format for all products now with the exception of the 4Mb x8,x16 and 1Mb x16 BGA. There is no plan to change back to the previous marking format.
In what environments or applications are Everspin toggle MRAM devices currently being used?
Automotive, industrial control equipment, servers, RAID systems, gaming machines, avionics and many more. Everspin MRAMs are applicable in any application that would use an SRAM or DRAM.
In a toggle MRAM when is the Write actually performed on a bit?
A write is performed on the rising edge of either of the CE#, WE# or U#/LB#.
SYSTEM DESIGN TECHNIQUE FOR MRAM
What are some system level design techniques that I could implement to reduce the risk of exposure to levels of external magnetic fields that may affect MRAM? Can I place an MRAM near motors or transformers?
Everspin MRAM has an absolute maximum magnetic field specification comparable to a Hard Disk drive. Everspin MRAM can be placed near motors or transformers as long as the magnetic field emanating from these components does not exceed the absolute maximum magnetic field specification at the location of the MRAM.
Are there any special handling requirements for shipping and receiving of MRAM?
There are no special handling requirements for shipping or receiving MRAM.
Are there any special handling requirements for board assembly using MRAM?
There are no special handling requirements for assembly of MRAM.
What is the value of the Curie Temperature Point for Everspin MRAM products?
The Curie temperature for thin films of NiFe that are used in Toggle MRAM are well above 300C. We have verified no loss of data in Everspin Toggle MRAM that has been heated to 250C for several hours.
ECCN, EAR99, EXPORT CONTROL CLASSIFICATION NUMBER
What is the Everspin Export Control Classification Number (ECCN)?
The Everspin Export Control Classification Number (ECCN) is EAR99.
ACCESS TIME, 35ns
Are there plans to develop parts with access times faster than 35ns for parallel interface MRAM in the near future?
Generally, not at this time for parallel interface MRAM.
MR20H40CDF, TERMINATION FINISH, TIN MATTE
What is the termination finish on the DFN package?
Tin Matte, applied by electroplating. Thickness 8/25um. No nickle barrier. Not annealed.
MR25H10, WRITE PROTECT, WEL, PROTECTED, STATUS REGISTER
The WP# pin on the device should Write Protect the Status Register after the SRWD bit is set in the Status Register. I have tried several different methods to get this to happen, but no matter what I do, I can write to the Status Register with the SRWD bit set and the WP# pin low.
See the Memory Protection Modes table in the data sheet. The WEL bit must be set to protect both protected as well as unprotected data blocks
MR25H10, PCB FOOTPRINT, EXPOSED PAD
Can you run traces underneath the exposed bottom pad on the DFN package? Does it need to be connected to ground?
The exposed pad on the bottom of the device is part of the lead frame which is internally connected to Vss. The optimal design is to place a ground pad on the PCB under the device and solder the bottom pad to it. While this is not a requirement, connecting the bottom pad to Vss will improve noise immunity and act as a heat sink. We recommend that you not route traces under the device.
MR0A08BSO35, CYPRESS, CY14B101LA-SZ25XIT, DROP IN REPLACEMENT
Is the MR0A08BSO35 a drop-in replacement for the Cypress CY14B101LA-SZ25XIT? If so are there any differences that need to be considered when designing with it vs. the CY14B101LA-SZ25XIT?
Yes, the MR0A08BSO35 will drop into the CY14B101LA-SZ25XIT. The only difference is the access time (35 ns vs. 25 ns). Also, the Everspin device does not require the "Software STORE" and "Software RECALL" commands. Reading from or writing to the address locations in the Everspin device required by the Cypress "Store/Restore" commands should not affect the Everspin device, so we do not believe you need to make software/firmware changes. However, we encourage your software team to conduct their own tests regarding this issue to confirm compatibility.
MR256A08, CY14B256LA-SZ25XI, CROSS REFERENCE
Do you have a cross for the Cypress part CY14B256LA-SZ25XI?
The cross for the Cypress CY14B256LA-SZ25XI is the MR256A08B.
Are there any differences that need to be considered if designing-in MR25H256 with the FM25V02 as an alternate source?
The MR25H256 is not a drop in replacement for the FM25V02. The Ramtron part is a 2-wire interface. Our device is a SPI interface (4-5 wire device, depending on how it's used).
MR25H40CDC, OPERATING, VOLTAGE, CLOCK SPEED, 2.5V
The datasheet says the minimum operating voltage for the MR25H40CDC is 3.0V. On the off chance that this information is available will it still function at 2.5V but at a lower clock speed?
The device may operate at the lower voltage, however, Everspin does not test this and does not warranty operation outside the data sheet parameters.
ERASE SPEED, PROGRAMMING MRAM SPI CONNECTION
What is the erase speed? If needed to erase all data asap, how long would it take?
MRAM does not have a block erase function like a Flash device. The time it takes to erase the entire device data would be the time required to write a known bit to each memory cell. It's a simple computation depending upon the device. Take the fastest write time by the number of words and that's your answer.
PACKAGE, ANNEAL, PLATING
Are the Everspin parts Annealed after the lead frame is plated?
Yes. 1 hour anneal @ 150C after lead frame tin plating is standard process for our assemblers.
PREPROGRAMMING MRAM, REFLOW
Can Everspin MRAM be programmed prior to assembly and solder reflow?
Yes. Our partner, Xeltek has developed pre-programming systems for Everspin MRAM. See their site at http://www.xeltek.com/superpro-supports-mram-technology.
Yes. 1 hour anneal @ 150C after lead frame tin plating is standard process for our assemblers