FM25040B
4-Kbit (512 × 8) Serial (SPI) Automotive
F-RAM
Cypress Semiconductor Corporation • 198 Champion Court • San Jose,CA 95134-1709 • 408-943-2600
Document Number: 001-86151 Rev. *D Revised August 9, 2016
4-Kbit (512 × 8) Serial (SPI) Automotive F-RAM
Features
■4-Kbit ferroelectric random access memory (F-RAM) logically
organized as 512 × 8
❐High-endurance 10 trillion (1013) read/writes
❐121-year data retention (See the Data Retention and
Endurance table)
❐NoDelay™ writes
❐Advanced high-reliability ferroelectric process
■Very fast serial peripheral interface (SPI)
❐Up to 14 MHz frequency
❐Direct hardware replacement for serial flash and EEPROM
❐Supports SPI mode 0 (0, 0) and mode 3 (1, 1)
■Sophistica te d w r ite protec ti on s cheme
❐Hardware protection using the Write Protect (WP) pin
❐Software protection using Write Disable instruction
❐Software block protection for 1/4, 1/2, or entire array
■Low power consumption
❐300 A active current at 1 MHz
❐10 A (typ) standby current at +85 C
■Voltage operation: VDD = 4.5 V to 5.5 V
■Automotive-E temperature: –40 C to +125 C
■8-pin small outline inte grated circuit (SOIC) package
■AEC Q100 Grade 1 compliant
■Restriction of hazardous substances (RoHS) compliant
Functional Description
The FM25040B is a 4-Kbit nonvolatile memory employing an
advanced ferroelectric process. A ferroelectric random access
memory or F-RAM is nonvolatile and performs reads and writes
similar to a RAM. It provides reliable data retention for 121 years
while eliminating the complexities, overhead, and system level
reliability problems caused by seri al flash, EEPROM, and othe r
nonvolatile memories.
Unlike serial flash and EEPROM, the FM25040B performs write
operations at bus speed. No write delays are incurred. Data is
written to the memory array immediately after each byte is
successfully transferred to the device. The next bus cycle can
commence without the need for data polling. In addition, the
product offers substantial write endura nce compared with other
nonvolatile memories. The FM25040B is capable of supporting
1013 read/write cycles, or 10 million times more write cycles than
EEPROM.
These capabilities make the FM25040B ideal for nonvolatile
memory applications requiring frequent or rapid writes.
Examples range from data collection, where the number of write
cycles may be critical, to demanding industrial controls where the
long write time of serial flash or EEPROM can cause data loss.
The FM25040B provides substantial benefits to users of serial
EEPROM or flash as a hardware drop-in replacement. The
FM25040B uses the high-speed SPI bus, which enhances the
high-speed write capability of F-RAM technology. The device
specifications are guaranteed over an automotive-e temperature
range of –40 C to +125 C.
For a complete list of related resources, click here.
Errata: The Write Enable Latch (WEL) bit in the Status Register of FM25040B p art doesn’t clear after exe cuting the memory write (W RITE) operation at memory location( s)
from 0x100 to 0x1FF. For more information, see Errata on page 19. Details include errata trigger conditions, scope of impact, available workarounds, and silicon revision
applicability.
Instruction Decoder
Clock Generator
Control Logic
Write Protect
Instruction Register
Address Register
Counter
512 x 8
F-RAM Array
9
Data I/ O Register
8
Nonvolatile Status
Register
2
WP
CS
HOLD
SCK
SOSI
Logic Block Diagram
FM25040B
Document Number: 001-86151 Rev. *D Page 2 of 22
Contents
Pinout ................................................................................3
Pin Definitions ..................................................................3
Functional Overview ................ ... .............. ... .............. ... ...4
Memory Architecture ................... ... .............. ... .............. ...4
Serial Peripheral Interface – SPI Bus ........................ ... ...4
SPI Overview ............ ... .............. ... .............. ... ..............4
SPI Modes ................... ... .............. ... .............. .. ............6
Power Up to First Access ............................................6
Command Structure ....................................................6
WREN - Set Write Enable Latch .................................6
WRDI - Reset Write Enable Latch ...............................6
Status Register and Write Protection .............................6
RDSR - Read Status Register .....................................7
WRSR - Write Status Register ....................................7
Memory Operation ............ ... .............. ... .............. ..............8
Write Operation ................. .............. .. .............. ............8
Read Operation ...........................................................8
HOLD Pin Operation ...................................................9
Endurance ................................................................. 10
Maximum Ratings ...........................................................11
Operating Range ..................... .. .............. ... .............. ... ....11
DC Electrical Characteristics ......................... ...............11
Data Retention and Endurance .....................................12
Example of an F-RAM Life Time
in an AEC-Q100 Automotive Application .....................12
Capacitance ....................................................................12
Thermal Resistance ........................................................12
AC Test Conditions ......................... .............. ... ..............12
AC Switching Characteristi cs .................... .............. .. ...13
Power Cycle Timing .......................................................15
Ordering Information ......................................................16
Ordering Code Definitions .........................................16
Package Diagram ............................................................17
Acronyms ........................................................................ 18
Document Conventions ..................... ... ... .............. ... .....18
Units of Measure ............. ... ... .............. ... .. .............. ...18
Errata ...............................................................................18
Part Numbers Affected ..............................................19
Qualification Status ............ .......................................19
Errata Summary ........................................................19
Document History Page ........................... ... .. .............. ...21
Sales, Solutions, and Legal Information ......................22
Worldwide Sales and Design Support .......................22
Products .................................................................... 22
PSoC®Solutions .......................................................22
Cypress Developer Community ...................... ... ........22
Technical Support .....................................................22
FM25040B
Document Number: 001-86151 Rev. *D Page 3 of 22
Pinout Figure 1. 8-pin SOIC pinout
HOLD
SCK
1
2
3
4 5
CS 8
7
6
VDD
SI
SO
Top View
not to scale
V
SS
WP
Pin Definitions
Pin Name I/O Type Description
CS Input Chip Select. This active LOW input activates the device. When HIGH, the device enters low-power
standby mode, ignores other inputs, and tristates the output. When LOW, the device internally
activates the SCK signal. A falling edge on CS must occur before every opcode.
SCK Input Serial Clock. All I/O activity is synchronized to the serial clock. Inputs are latched on the rising edge
and outputs occur on the falling edge. Because th e device is synchronous, th e cl ock freq uency may
be any value between 0 and 14 MHz and may be interrupted at any time.
SI[1] Input Serial Input. All data is input to the device on this pin. The pin is sampled on the rising edge of SCK
and is ignored at other times. It should always be driven to a valid logic level to meet IDD specifications.
SO[1] Output Serial Output. This is the data output pin. It is driven during a read and remains tristated at all other
times including when HOLD is LOW. Data transitions are driven on the falling edge of the serial clock.
WP Input Write Protect. This active LOW pin prevents all write operation, including Status Register. If HIGH,
write access is determined by the other write protection features, as controlled through the Status
Register. A complete explanation of write protection is provided in Status Register and Write Protection
on page 7. This pin must be tied to VDD if not use d .
HOLD Input HOLD Pin. The HOLD pin is used when the host CPU must interrupt a memory operation for another
task. When HOLD is LOW, the current operation is suspended. The device ignores any transition on
SCK or CS. All transitions on HOLD must occur while SCK is LOW. This pin must be tied to VDD if not
used.
VSS Power supply Ground for the device. Must be connected to the ground of the system.
VDD Power supply Power supply input to the device.
Note
1. SI may be connected to SO for a single pin data interface.
FM25040B
Document Number: 001-86151 Rev. *D Page 4 of 22
Functional Overview
The FM25040B is a serial F-RAM memory . The memory array is
logically organized as 512 × 8 bits and is accessed using an
industry standard serial peripheral interface (SPI) bus. The
functional operation of the F-RAM is similar to serial flash and
serial EEPROMs. The major difference between the FM25040B
and a serial flash or EEPROM with the same pinout is the
F-RAM’s superior write performance, high endurance, and low
power consumption. The FM25040B differs from Cypress’s
FM25040 by increasing its performance to 14 MHz and adding
support for SPI Mode 3. This makes the FM25040B a drop-in
replacement for most 4-Kbit SPI EEPROMs that support Modes
0 & 3.
Memory Architecture
When accessing the FM25040B, the user addresses 512
locations of eight data bits each. These eight data bits are shifted
in or out serially. The addresses are accessed using the SPI
protocol, which includes a chip select (to permit multiple devices
on the bus), an opcode including the upper address bit, and a
word address. The word address consist of the lower 8-address
bits. The complete address of 9 bits specifies each byte address
uniquely.
Most functions of the FM25040B are either controlled by the SPI
interface or handled by on-board circuitry. The access time for
the memory operation is essentially zero, beyond the time
needed for the serial protocol. That is, the memory is read or
written at the speed of the SPI bus. Unlike a serial flash or
EEPROM, it is not necessary to poll the device for a ready
condition beca us e wr it es oc cur at b us sp eed . B y the time a n ew
bus transaction can be shifted into the device , a write operation
is complete. This is explained in more detail in the interface
section.
Note The FM25040B contains no power management circuits
other than a simple internal power-on reset circuit. It is the user’s
responsibility to ensure that VDD is within datasheet tolerances
to prevent incorrect operation. It is recommended that the part is
not powered down with chip enabl e active.
Serial Peripheral Interface – SPI Bus
The FM25040B is a SPI slave device and operates at speeds up
to 14 MHz. This high-speed serial bus provides
high-performance serial communication to a SPI master. Many
common microcontrollers have hardware SPI ports allowing a
direct interface. It is quite simple to emulate the port using
ordinary port pins for microcontrollers that do not. The
FM25040B operates in SPI Mode 0 and 3.
SPI Overview
The SPI is a four-pin interface with Chip Select (CS), Serial Input
(SI), Serial Output (SO), and Serial Clock (SCK) pins.
The SPI is a synchronous serial interface, which uses clock and
data pins for memory access and su pports multiple devices on
the data bus. A device on the SPI bus is activated using the CS
pin.
The relationship between chip select, clock, and data is dictated
by the SPI mode. This device supports SPI modes 0 and 3. In
both of these modes, data is clocked into the F-RAM on the rising
edge of SCK starting from the first rising edge after CS goes
active.
The SPI protocol is controlled by opcodes. These opcodes
specify the commands from the bus master to the sl ave de vice.
After CS is activated, the first byte transferred from the bus
master is the opcode. Following the opcode, any addresses and
data are then transferred. The CS must go inactive after an
operation is comple te and befo re a new opcod e can be issue d.
The commonly used terms in the SPI protocol are as follows:
SPI Master
The SPI master device controls the operations on a SPI bus. An
SPI bus may have only one master with one or more slave
devices. All the slaves share the same SPI bus lines and the
master may select any of the slave devices using the CS pin. All
of the operations must be initiated by the master activating a
slave device by pulling the CS pin of the slave LOW . The master
also generates the SCK and all the data transmission on SI and
SO lines are synchronized with this clock.
SPI Slave
The SPI slave device is activated by the master through the Chip
Select line. A slave device gets the SCK as an input from the SPI
master and all the communication is synchronized with this
clock. An SPI slave never initiates a communication on the SPI
bus and acts only on the instruction from the master.
The FM25040B operates as an SPI slave and may share the SPI
bus with other SPI slave devices.
Chip Select (CS)
To select any slave device, the master needs to pull down the
corresponding CS pin. Any instruction can be issued to a slave
device only while the CS pin is LOW. When the device is not
selected, data through the SI pin is ignored and the serial output
pin (SO) remains in a high-impedan ce state.
Note A new instruction must begin with the falling edge of CS.
Therefore, only one opcode can be issued fo r each active Chip
Select cycle.
Serial Clock (SCK)
The Serial Clock is generated by the SPI master and the
communication is synchronized with this clock after CS goes
LOW.
The FM25040B enables SPI modes 0 and 3 for data
communication. In both of these modes, the inputs are latched
by the slave device on the rising edge of SCK and ou tputs are
issued on the falling edge. Therefore, the first rising edge of SCK
signifies the arrival of the first bit (MSB) of a SPI instruction on
the SI pin. Further, all data inputs and outputs are synchronized
with SCK.
FM25040B
Document Number: 001-86151 Rev. *D Page 5 of 22
Data Transmission (SI/SO)
The SPI data bus consists of two lines, SI and SO, for serial data
communication. SI is also referred to as Master Out Slave In
(MOSI) and SO is referred to as Master In Slave Out (MISO). The
master issues instructions to the slave through the SI pin, while
the slave responds through the SO pin. Multiple slave devices
may share the SI and SO lines as described earlier.
The FM25040B has two separate pins for SI and SO, which can
be connected with the master as shown in Figure 2.
For a microcontroller that has no dedicated SPI bus, a
general-purpose port may be used. To reduce hardware
resources on the controller , it is possible to connect the two data
pins (SI, SO) together and tie off (HIGH) the HOLD and WP pins.
Figure 3 shows such a configuration, which uses only three pins.
Most Significant Bit (MSB)
The SPI protocol requires that the first bit to be transmitted is the
Most Significant Bit (MSB). This is valid for both address and
data tran s missi on .
The 4-Kbit serial F-RAM requires an opcode including the upper
address bit, and a word address for any read or write operation.
The word address consist of the lower 8-address bits. The
complete address of 9 bits specifies each byte address uniquely .
Serial Opcode
After the slave device is selected with CS going LOW, the first
byte received is treated as the opcode for the intended operation.
FM25040B uses the standard opcodes for memory accesses.
Invalid Opcode
If an invalid opcode i s received, the opcode is ignored and the
device ignores any additio nal serial data on the SI pin until the
next falling edge of CS, and the SO pin remains tristated.
Status Register
FM25040B has an 8-bit Status Register. The bits in the Status
Register are used to configure the device. These bits are
described in Table 3 on page 7.
Figure 2. System Configuration with SPI port
Figure 3. System Configuration without SPI port
CS1
CS2
HOLD1
HOLD2
FM25040B FM25040B
WP1
WP2
SCK SI SO SCK SI SO
CS HOLD WP CS HOLD WP
SCK
MOSI
MISO
SPI
Microcontroller
FM25040B
Microcontroller
SCK SI SO
CS HOLD WP
P1.2
P1.1
P1.0
FM25040B
Document Number: 001-86151 Rev. *D Page 6 of 22
SPI Modes
FM25040B may be driven by a microcontroller with its SPI
peripheral running in either of the following two modes:
■SPI Mode 0 (CPOL = 0, CPHA = 0)
■SPI Mode 3 (CPOL = 1, CPHA = 1)
For both these modes, the input data is latched i n on the rising
edge of SCK starting from the first rising edge after CS goes
active. If the clock starts from a HIGH state (in mode 3), the first
rising edge after the clock toggles is considered. The output data
is available on the falling edge of SCK.
The two SPI modes are shown in Figure 4 on page 6 and Figure
5 on page 6. The status of the clock when the bus master is not
transferring data is:
■SCK remains at 0 for Mode 0
■SCK remains at 1 for Mode 3
The device detects the SPI mode from the status of the SCK pin
when the device is selected by bringi ng the CS pin LOW. If the
SCK pin is LOW when the device is selected, SPI Mode 0 is
assumed and if the SCK pin is HIGH, it works in SPI Mode 3.
Power Up to First Access
The FM25040B is no t accessible for a tPU time after power up.
Users must comply with the timing parameter tPU, which is the
minimum time from VDD (min) to the first CS LOW.
Command Structure
There are six commands, called opcodes, that can be issued by
the bus master to the FM25040B. They are listed in Table 1.
These opcodes control the functions performed by the memory.
WREN - Set Write Enable Latch
The FM25040B will power up with writes d isabled. The WREN
command must be issued before any write operation. Sending
the WREN opcode allows the user to issue subsequent opcodes
for write operations. These include writing the Status Register
(WRSR) and writing the memory (WRITE).
Sending the WREN opcode causes the internal Write Enable
Latch to be set. A flag bit in the Status Register, called WEL,
indicates the state of the latch. WEL = ’1’ indicates that writes are
permitted. Attempting to write the WEL bit in the Status Register
has no effect on the state of this bit – only the WREN opcode can
set this bit. The WEL bit will be automatically cleared on the rising
edge of CS following a W RDI, a WRSR, or a WRIT E opera tion.
This preve nt s f ur ther wr it es to the Status Register or the F-RAM
array without another WREN command. Figure 6 illustrates the
WREN command bus configuration.
Note: The Write Enable Latch (WEL) bit in the Status Register
of FM25040B part doesn’t clear after executing the memory write
(WRITE) operation at memory location(s) from 0x100 to 0x1 FF.
For more information, see Errat a on page 19.
WRDI - Reset Write Enable Latch
The WRDI command disables all write activity by clearing the
Write Enable Latch. The user can verify that writes are disabled
by reading the WEL bit in the Status Register an d verifying that
WEL is equal to ‘0’. Figure 7 illustrates the WRDI command bus
configuration.
Figure 4. SPI Mode 0
Figure 5. SPI Mode 3
LSB
MSB
76543210
CS
SCK
SI
012 3 4 567
Table 1. Opcode comma nd s
Name Description Opcode
WREN Set write enable latch 0000 0110b
WRDI Write disable 0000 0100b
RDSR Read Status Register 0000 0101b
WRSR Write Status Register 0000 0001b
READ Read memory data 0000 A011b
WRITE Write memory data 0000 A010b
Figure 6. WREN Bus Configuration
Figure 7. WRDI Bus Configuration
0 0 0 0 0 1 1 0
CS
SCK
SI
SO
HI-Z
0 1 2 3 4 5 6 7
0 0 0
CS
SCK
SI
SO
HI-Z
0 1 2 3 4 5 6 7
00
001
FM25040B
Document Number: 001-86151 Rev. *D Page 7 of 22
Status Register and Write Protection
The write protection features of the FM25040B are multi-tiered
and are enabled through the status register. First, a WREN
opcode must be issued prior to any write operation. Assuming
that writes are enabled using WREN, writes to memory are
controlled by the WP pin and the Status Register. Wh en WP is
LOW, the entire part is write-protected. When WP is HIGH, the
memory protection is subject to the S tatus Register . Writes to the
Status Register are performed using the WREN and WRSR
commands and subject to the WP pin. The Status Register is
organized as follows. (The default value shipped from the factory
for bits in the Status Register is ‘0’.)
Bits 0 and 4-7 are fixed at ‘0’; none of these bits can be modified.
Note that bit 0 (“Ready or Write in progress” bit in serial flash and
EEPROM) is unnecessary, as the F-RAM writes in real-time and
is never busy, so it reads out as a ‘0’. Th e BP1 and BP0 control
the software write-protection features and are nonvolatile bits.
The WEL flag indicates the state of the Write Enable Latch.
Attempting to directly write the WEL bit in the S tatus Register has
no effect on its state. This bit is internally set and cleared via the
WREN and WRDI commands, respectively.
BP1 and BP0 are memory block write protection bits. They
specify portions of memory that are write-protected as shown in
Table 4.
The BP1 and BP0 b its and the Write Enable Latch are the onl y
mechanisms that protect the memory from writes. The remaining
write protection features protect inadvertent changes to the block
protect bits.
The BP1 and BP0 bits allow software to selectively write protect
the array. These settings are only used when the WP pin is
inactive and the WREN command has been issued.
Table 5 summarizes the write protection conditions.
RDSR - Read Status Register
The RDSR command allows the bus master to verify the
contents of the Status Register. Reading the status register
provides information about the current state of the
write-protection features. Following the RDSR opcode, the
FM25040B will return one byte with the contents of the Status
Register.
WRSR - Write Status Register
The WRSR command allows the SPI bus master to write into the
Status Register and change the write protect configuration by
setting the BP0 and BP1 bits as required. Before issuing a
WRSR command, the WP pin must be HIGH or inactive. Note
that on the FM25040B, WP prevents writing to the Status
Register and the memory array. Before sending the WRSR
command, the user must send a WREN command to enable
writes. Executing a WRSR command is a write operation and
therefore, clears the Write Enable Latch.
Table 2. Status Register
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
X (0) X (0) X (0) X (0) BP1 (0) BP0 (0) WEL (0) X (0)
Table 3. Sta t us Register Bit Definition
Bit Definition Description
Bit 0 Don’t care This bit is non-writable and always returns ‘0’ upon read.
Bit 1 (WEL) Write Enable Latch WEL indicates if the device is write enabled. This bit defaults to ‘0’ (disabled) on power-up.
WEL = '1' --> Write enabled
WEL = '0' --> Write disabled
Bit 2 (BP0) Block Protect bit ‘0’ Used for block protection. For details, see Table 4 on page 7.
Bit 3 (BP1) Block Protect bit ‘1’ Used for block protection. For details, see Table 4 on page 7.
Bit 4-7 Don’t care These bits are non-writable and always return ‘0’ upon read.
Table 4. Block Memory Write Protection
BP1 BP0 Protected Address Range
0 0 None
0 1 180h to 1FFh (upper 1/4)
1 0 100h to 1FFh (upper 1/2)
1 1 000h to 1FFh (all)
Table 5. Write Protectio n
WEL WP Protected
Blocks Unprotected
Blocks Status
Register
0 X Protected Protected Protected
1 0 Protected Protected Protected
1 1 Protected Unprotected Unprotected
FM25040B
Document Number: 001-86151 Rev. *D Page 8 of 22
Memory Operation
The SPI interface, which is capable of a high clock frequency,
highlights the fast write capability of the F-RAM technology.
Unlike serial flash an d EEPROMs, the FM25040B can perform
sequential writes at b us speed. No page register is needed and
any number of sequential writes may be performed.
Write Operation
All writes to the memory begin with a WREN opcode. The WRITE
opcode includes the upper bit of the memory address. Bit 3 in the
opcode corresponds to the upper address bit (A8). The next byte
is the lower 8-bits of the address (A7-A0). In total, the 9-bits
specify the address of the first byte of the write operation.
Subsequent bytes are data bytes, which are written sequentially .
Addresses are incremented internally as long as the bus master
continues to issue clocks and keeps CS LOW . If the last address
of 1FFh is reached, the counter will roll over to 000h. Data is
written MSB first. The rising edge of CS terminates a write
operation. A write operation is shown in Figure 10.
Note When a burst write reaches a protected block address, the
automatic address increment sto ps and all the subsequent da ta
bytes received for write will be ignored by the device.
EEPROMs use page buffers to increase their write throughput.
This compensates for the technology's inherently slow write
operations. F-RAM memories do not have page buffers because
each byte is written to the F-RAM array immediately after it is
clocked in (after the eighth clock). This allows any number of
bytes to be written without page buffer delays.
Note If the power is lost in the middle of the write operation, only
the last completed byte will be written.
Read Operation
After the falling edge of CS, the bu s master can issue a READ
opcode. The READ opcode includes the upper bit of the memory
address. Bit 3 in the opcode corresponds to the upper add ress
bit (A8). The next byte is the lower 8-bits of the address (A7-A0).
In total, the 9-bits specify the address of the first byte of the read
operation. After the opcode and address are issued, the device
drives out the read data on the next eight clocks. The SI input is
ignored during read data bytes. Subsequent bytes are data
bytes, which are read out sequentially. Addresses are
incremented internally as long as the bus master continues to
issue clocks and CS is LOW. If the last address of 1FFh is
reached, the counter will roll over to 000h. Data is read MSB first.
The rising edge of CS terminates a read op eration and tristates
the SO pin. A read operation is shown in Figure 11.
Figure 8. RDSR Bus Configuration
Figure 9. WRSR Bus Configuration (WREN not shown)
CS
SCK
SO
01234567
SI
000001 0 0
1
HI-Z
012345 67
LSB
D0D1D2D3D4D5D6
MSB
D7
Opcode
Data
CS
SCK
SO
0123 4567
SI
00000001
MSB LSB
D2D3X
HI-Z
01234567
Opcode Data
XX
XX
X
FM25040B
Document Number: 001-86151 Rev. *D Page 9 of 22
HOLD Pin Operation
The HOLD pin can be used to interrupt a serial operation without
aborting it. If the bus master pulls the HOLD pin LOW whi le SCK
is LOW, the current operati on will pause. Taking the HOLD pin
HIGH while SCK is LOW will resume an operation. The
transitions of HOLD must occur while SCK is LOW , but the SCK
and CS can toggle during a hold state.
Figure 10. Memory Write (WREN not shown)
Figure 11. Memory Read
CS
SCK
SO
01234 5 6 70 7654321 01234567
MSB LSB
Data
D0D1D2D3D4D5D6D7
SI
Opcode
0000
A8
01
A7 A6 A5 A4 A3 A1
0
A2
A0
Byte Address
MSB LSB
HI-Z
CS
SCK
SO
01 23456 70 7654321 012345 6 7
MSB LSB
Data
SI
Opcode
0000
A8
01
A7 A6 A5 A4 A3 A1
1
A2
A0
Byte Address
MSB LSB
D0D1D2D3D4D5D6D7
HI-Z
Figure 12. HOLD Operation[2]
CS
SCK
HOLD
SO
~
~
~
~
SI VALID IN VALID IN
~
~
~
~
~
~
Note
2. Figure shows HOLD operation for input mode and output mode.
FM25040B
Document Number: 001-86151 Rev. *D Page 10 of 22
Endurance
The FM25040B devices are capable of being accessed at le ast
1013 times, reads or writes. An F-RAM memory operates with a
read and restore mechan ism. Therefor e, an endurance cycl e is
applied on a row basis for each access (read or write) to the
memory array. The F-RAM architecture is b ased on an array of
rows and columns of 64 rows of 64-bits each. The entire row is
internally accessed once whether a single byte or all eight bytes
are read or written. Each byte in the row is counted only once in
an endurance calculation. Table 6 shows endurance calculations
for a 64-byte repeating loop, which includes an opcode, a starting
address, and a sequential 64-byte data stream. This causes
each byte to experience one endurance cycle through the loop.
Table 6. Time to Reach Endurance Limit for Repeating
64-byte Loop
SCK Freq
(MHz) Endurance
Cycles/sec Endurance
Cycles/year Years to Reach
Limit
10 18,660 5.88 × 1011 17.0
5 9,330 2.94 × 1011 34.0
1 1,870 5.88 × 1010 170.1
FM25040B
Document Number: 001-86151 Rev. *D Page 11 of 22
Maximum Ratings
Exceeding maximum ratings may shorten the useful life of the
device. These user guidelines are not tested.
Storage temperature ................................–55 C to +150 C
Maximum accumulated storage time
At 150 °C ambient temperature .............. .. ... .............. 1000 h
At 125 °C ambient temperature .............. .. ... .............11000 h
At 85 °C ambient temperature .............................. 121 Years
Ambient temperature
with power applied ...................................–55 °C to +125 °C
Supply voltage on VDD relative to VSS .........–1.0 V to +7.0 V
Input voltage .............–1.0 V to +7.0 V and VIN < VDD+1.0 V
DC voltage applied to outputs
in High Z state ............................ ... .....–0.5 V to VDD + 0.5 V
Transient voltage (< 20 ns)
on any pin to ground potential ............–2.0 V to VDD + 2.0 V
Package power dissipation capability (TA = 25 °C) .....1.0 W
Surface mount lead
soldering temperature (3 seconds) .......................... +260 C
DC output current (1 output at a time , 1s duration) ....15 mA
Electrostatic Discharge Voltage
Human Body Model (AEC-Q100-002 Rev. E) ................ 3.5 kV
Charged Device Model (AEC-Q100-011 Rev. B) ........... 1.25 kV
Machine Model (AEC-Q100-003 Rev. E) ..........................250 V
Latch up current .....................................................> 140 mA
Operating Range
Range Ambient Temperature (T A) VDD
Automotive-E –40 C to +125 C 4.5 V to 5.5 V
DC Electrical Characteristics
Over the Operating Range
Parameter Description Test Conditions Min Typ [3] Max Unit
VDD Power supply 4.5 5.0 5.5 V
IDD VDD supply current SCK toggling between
VDD – 0.3 V and VSS,
other inputs
VSS or VDD – 0.3 V.
SO = Open.
fSCK = 1 MHz – – 0.3 mA
fSCK = 14 MHz – – 3 mA
ISB VDD standby current CS = VDD. All other
inputs VSS or VDD.TA = 85 °C – – 10 A
TA = 125 °C – – 30 A
ILI Input leakage current VSS < VIN < VDD ––±1A
ILO Output leakage current VSS < VOUT < VDD ––±1A
VIH Input HIGH voltage 0.75 × VDD –V
DD + 0.3 V
VIL Input LOW voltage – 0.3 – 0.25 × VDD V
VOH Output HIGH voltage IOH = –1 mA VDD – 0.8 – – V
VOL Output LOW voltage IOL = 2 mA – – 0.4 V
VHYS[4] Input Hysteresis (CS and SCK pin) 0.05 × VDD ––V
Notes
3. Typical values are at 25 °C, V DD = VDD(typ). Not 100% tested.
4. This parameter is characterized but no t 100% tested.
FM25040B
Document Number: 001-86151 Rev. *D Page 12 of 22
AC Test Conditions
Input pulse levels .................................10% and 90% of VDD
Input rise and fall times ...................................................5 ns
Input and output timing reference levels ................0.5 × VDD
Output load capacitance ..............................................30 pF
Data Retention and Endurance
Parameter Description Test condition Min Max Unit
TDR Dat a re tention TA = 125 C 11000 – Hours
TA = 105 C11–Years
TA = 85 C 121 –
NVCEndurance Over operating temperature 1013 – Cycles
Example of an F-RAM Life Time in an AEC-Q100 Automotive Application
An application does not operate under a steady temperature for the entire usage life time of the application. Instead, it is often expected
to operate in multiple temperature environments throughout the application’s usage life time. Accord ingly, the retention specification
for F-RAM in applications often needs to be cal cu lated cumulatively. An example calculation fo r a multi-temperature thermal profiles
is given below.
Tempeature
TTime Factor
t
Acceleration Factor with respect to Tmax
A [5] Profile Factor
PProfile Life Time
L (P)
T1 = 125 C t1 = 0.1 A1 = 1
8.33 > 10.46 Years
T2 = 105 C t2 = 0. 15 A2 = 8.67
T3 = 85 C t3 = 0.25 A3 = 95.68
T4 = 55 C t4 = 0.50 A4 = 6074.80
ALT
LTmax
------------------------ e
Ea
k
------- 1
T
--- 1
Tmax
----------------
–


==
P1
t1
A1
------- t2
A2
------- t3
A3
------- t4
A4
-------
+++


--------------------------------------------------------
=
LP PLTmax=
Capacitance
Parameter [6] Description Test Conditions Max Unit
COOutput pin capacitance (SO) TA = 25 C, f = 1 MHz, VDD = VDD(typ) 8 pF
CIInput pin capacitance 6pF
Thermal Resist ance
Parameter Description Test Conditions 8-pin SOIC Unit
JA Thermal resistance
(junction to ambient) Test conditions follow standard test methods and
procedures for measuring thermal impedance, per EIA /
JESD51.
148 C/W
JC Thermal resistance
(junction to case) 48 C/W
Notes
5. Where k is the Boltzmann constant 8.617 × 10-5 eV/K, Tmax is th e hig hest temperat ure specif ied for the prod uct, and T is any t empe rature wit hin the F-RAM p rodu ct
specification. All temperature s are in Kelvin in the equation.
6. This parameter is characterized but not 100% tested.
FM25040B
Document Number: 001-86151 Rev. *D Page 13 of 22
AC Switching Characteristics
Over the Operating Range
Parameters [7]
Description Min Max Unit
Cypress
Parameter Alt. Parameter
fSCK –SCK Clock frequency 014 MHz
tCH –Clock HIGH time 30 –ns
tCL –Clock LOW time 30 –ns
tCSU tCSS Chip select setup 10 –ns
tCSH tCSH Chip select hold 10 –ns
tOD[8, 9] tHZCS Output disable time –25 ns
tODV tCO Output data valid time –30 ns
tOH –Output hold time 0 – ns
tD–Deselect time 80 –ns
tR[10, 11] –Data in rise ti me –50 ns
tF[10, 11] –Data in fall t i me –50 ns
tSU tSD Data setup time 5 – ns
tHtHD Data hold time 5 – ns
tHS tSH HOLD setup time 10 –ns
tHH tHH HOLD hold time 10 –ns
tHZ[8, 9] tHHZ HOLD LOW to HI-Z –25 ns
tLZ[9] tHLZ HOLD HIGH to data active –25 ns
Notes
7. Test conditions assume a signal transition time of 5 ns or less, timing reference levels of 0.5 × VDD, input pulse levels of 10% to 90% of VDD, and output loading of
the specified I OL/IOH and 30 pF load capacitance shown in AC Test Conditions on page 12.
8. tOD and tHZ are specified with a load cap acitance of 5 pF. Transition is measured when the outputs enter a high impedance state.
9. This parameter is characterized but not 100% tested.
10.Rise and fall times measured between 10% and 90% of wavef orm.
11. These parameters are guaranteed by design and are not tested.
FM25040B
Document Number: 001-86151 Rev. *D Page 14 of 22
Figure 13. Synchronous Data Timing (Mode 0)
Figure 14. HOLD Timin g
HI-Z
VALID IN
HI-Z
CS
SCK
SI
SO
tCL
tCH
tCSU
tSU tH
tODV tOH
t
D
tCSH
tOD
VALID IN VALID IN
CS
SCK
HOLD
SO
tHS
tHZ tLZ
tHH
tHS
tHH
~
~
~
~
SI
tSU
VALID IN VALID IN
~
~
~
~
~
~
FM25040B
Document Number: 001-86151 Rev. *D Page 15 of 22
Power Cycle Timing
Over the Operating Range
Parameter Description Min Max Unit
tPU Power-up VDD(min) to first access (CS LOW) 1 – ms
tPD Last access (CS HIGH) to power-down (VDD(min)) 0 – µs
tVR [12] VDD power-up ramp rate 30 –µs/V
tVF [12] VDD power-down ramp rate 20 –µs/V
Figure 15. Power Cycle Timing
CS
~
~
~
~
tPU
tVR tVF
VDD
VDD(min)
tPD
VDD(min)
Note
12.Slope measured at any point on VDD waveform.
FM25040B
Document Number: 001-86151 Rev. *D Page 16 of 22
Ordering Code Definitions
Ordering Information
Ordering Code Package
Diagram Package Type Operating
Range
FM25040B-GA 51-85066 8-pin SOIC Automotive-E
FM25040B-GATR 51-85066 8-pin SOIC
All these parts are Pb-free. Contact your local Cypress sales representative for availability of these part s.
Option: X = blank or TR
blank = Standard; TR = Tape and Reel
Temperature Range:
A = Automotive-E (–40 C to +125 C)
Package Type:
G = 8-pin SOIC
Die revision: B
Density: 040 = 4-Kbit
SPI F-RAM
Cypress
25FM 040 B - A
G X
FM25040B
Document Number: 001-86151 Rev. *D Page 17 of 22
Package Diagram F igure 16. 8-pin SOIC (150 Mils) Package Outline, 51-85066
51-85066 *H
FM25040B
Document Number: 001-86151 Rev. *D Page 18 of 22
Acronyms Document Conventions
Units of Measure
Acronym Description
AEC Automotive Electronics Council
CPHA Clock Phase
CPOL Clock Polarity
EEPROM Electrically Erasable Programmable Read-Only
Memory
EIA Electronic Industries Alliance
I/O Input/Output
JEDEC Joint Electron De vices Engineering Council
JESD JEDEC Standards
LSB Least Significant Bit
MSB Most Significant Bit
F-RAM Ferroelectric Random Access Memory
RoHS Restriction of Hazardous Substances
SPI Serial Peripheral Interface
SOIC Small Outline Integrated Circuit
Symbol Unit of Measure
°C degree Celsius
Hz hertz
kHz kilohertz
Kkilohm
Kbit kilobit
kV kilovolt
MHz megahertz
Amicroampere
smicrosecond
mA milliampere
ms millisecond
ns nanosecond
ohm
%percent
pF picofarad
Vvolt
Wwatt
FM25040B
Document Number: 001-86151 Rev. *D Page 19 of 22
Errata
This section describes the errata for the 4Kb SPI F-RAM (512 × 8 , SPI) products. Details include errata trigger condi tions, scope of
impact, available workarounds, and silicon revision applicability. Compare this document with the device datasheet for complete
functional differences.
Contact your local Cypress Sales Representative if you have questions. You can also send your related queries directly to
FRAM@cypress.com.
Part Numbers Affected
Qualification Status
Production parts.
Errata Summary
The following table defines the errata applicability.
1. The Write Enable Latch (WEL) bit in the Status Register of FM25040B part doesn’t clear after executing the memory write (WRITE)
operation at memory location(s) from 0x100 to 0x1FF.
■Problem Definition
As per the FM25040B datasheet “sending the WREN opcode causes the internal Write Enable Latch (WEL) to be set. A flag bit in
the status register, called WEL, indicates the state of the latch. WEL=1 indicates that writes are permitted. Attempting to write the
WEL bit in the status register has no effect. Completing any write operation will automatically clear the write-enable latch and will
prevent further writes without another WREN command ”.
However, in the FM25040B part, the WEL bit doesn’t clear automatically after writing at any memory location(s) from 0x100 to
0x1FF. That means, after completing the write cycle with the opcode byte 0x0A, WEL bit in status register is still set and hence a
further write can be issued without sending the WREN opcode.
Part Number Device Characteristics
FM25040B 512 × 8, 4.5 V to 5.5 V, sin gle po wer supply, serial (SPI) interface F-RAM in 8-pin SOIC package.
Items Part Number Silicon Revision Fix Status
The Write Enable Latch (WEL) bit in the
Status Register of FM25040B part doesn’t
clear after executing the memory write
(WRITE) operation at memory location(s)
from 0x100 to 0x1FF.
FM25040B-GA
FM25040B-GATR Rev *A None. This behavior is applicable
to all listed parts in the production.
FM25040B
Document Number: 001-86151 Rev. *D Page 20 of 22
Status Register
Status Register Bit Definition
The internal state machine of FM25040B is intended to clear the WEL bit after executing write opcodes (WRITE and WRSR).
However , as explained above, the WEL doesn’t clear when executing the memory write (WRITE) at location/s from 0x100 to 0x1FF.
The 4Kb memory requires 9 address bits to map the entire memory array (512 x 8). To optimize the command cycle and to maintain
the compatibility with the industry standard 4Kb SPI EEPROMs, the MSB of the address (9th bit) in the 4Kb device is embedded
into write (WRITE) and read (READ) opcodes as shown below.
For address range – 0x00 to 0xFF:
WRITE opcode – 0000 A010 = 0x0000 0010 (or 0x02 in hex, A = ‘0’)
READ opcode – 0000 A011 = 0x0000 0011 (or 0x03 in hex, A = ‘0’)
For address range – 0x100 to 0x1FF:
WRITE opcode – 0000 A010 = 0x0000 1010 (or 0x0A in hex, A = ‘1 ’)
READ opcode – 0000 A011 = 0x0000 1011 (or 0x0B in hex, A = ‘1’)
Due to a logic bug in the FM25040B state machine, the opcode byte 0x0A does not trigger clearing of WEL bit, hence the WEL bit
remains set even after executing the memory write at address location/s from 0x100 to 0x1FF.
■Parameters Affected
None.
■Trigger Condition(S)
Execute the Write Enable command (WREN) followed by the write command (WRITE) to memory address range 0x100 to 0x1FF.
■Scope of Impact
None. It only allows a subsequent write (WRITE or WRSR) without sending a prior WREN command.
■Workaround
To ensure that the WEL bit is cleared after every write, the SPI host controller can issue the Write Disable (WRDI) opcode at the
end of every write cycle (after CS goes high). The WRDI command clears the WEL (if set) and disables all writes until the WEL is
set by sending the WREN opcode before initiating a new write operation.
■Fix Status
There is no fix planned and all the FM25040B part in production will continue with the above errata.
FM25040B
Document Number: 001-86151 Rev. *D Page 21 of 22
Document History Page
Document Title: FM25040B, 4-Kbit (512 × 8) Serial (SPI) Automotive F-RAM
Document Number: 001-86151
Rev. ECN No. Orig. of
Change Submission
Date Description of Change
** 3912930 GVCH 02/25/2013 New spec
*A 4227042 GVCH 02/04/2014 Converted to Cypress standard format
Updated Maximum Ratings tab le
- Removed Moisture Sensitivity Level (MSL)
- Added junction temperature and latch up current
Updated Data Retention and Endura nce table
Added “Example of an F-RAM Life T ime in an AEC-Q100 Automotive Applica-
tion” table
Added footnote 5
Added Thermal Resistance table
Removed Package Marking Scheme (top mark)
Removed Ramtron revision history
Completing Sunset Review.
*B 4724387 PSR 04/14/2015 Updated Functional Description:
Added “For a complete list of related resources, click here.” at the end.
Updated Package Diagram:
spec 51-85066 – Changed revision from *F to *G.
Updated to new te mplate.
*C 4884720 ZSK / PSR 08/14/2015 Updated Maximum Ratings:
Updated ratings of “Storage temperature” (Replaced “+125 °C” with “+150 C”).
Removed “Maximum junction temperature”.
Added “Maximum accumulated storage time”.
Added “Ambient temperature with power applied”.
*D 5397042 GVCH 08/09/2016 Updated Serial Peripheral Interface – SPI Bus:
Updated WREN - Set Write Enable Latch:
Updated description (Added no te regarding Errata).
Updated Package Diagram:
spec 51-85066 – Changed revision from *G to *H.
Added Errata.
Updated to new te mplate.
Document Number: 001-86151 Rev. *D Revised August 9, 2016 Page 22 of 22
FM25040B
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