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p re - production thi s is a product in the pre - production phase of development . device ramtron international corporation c haracter ization is complete and ramtron does not expect to change 1850 ramtron dri ve, colorado springs, co 80921 t he specifications. ramtron will issue a product change notice if any (800) 545 - fram, (719) 481 - 7000 s pecification changes are made . http:// www.ramtron.com rev. 2.0 dec. 2011 page 1 of 11 fm 18w08 256kb wide voltage bytewide f - ram features 256kbit ferroelectric nonvolatile ram ? organized as 32,768 x 8 bits ? high endurance 1 00 trillion (10 1 4 ) read/writes ? 38 year data retention ? nodelay? writes ? advanced high - reliability ferroelectric proces s superior to bbsram modules ? no battery concerns ? monolithic reliability ? true surface mount solution, no rework steps ? superior for moisture, shock, and vibration ? resistant to negative voltage undershoots sram & eeprom compatible ? jedec 32kx8 sram & eep rom pinout ? 70 ns access time ? 130 ns cycle time low power operation ? wide voltage operation 2 .7v to 5. 5v ? 12 ma active current ? 20 ? a (typ.) standby current industry standard configuration ? industrial temperature - 40 ? c to +85 ? c ? 28 - pin green/rohs soic pack age description the fm 18w08 is a 256 - kilobit nonvolatile memory employing an advanced ferroelectric process. a ferroelectric random access memory or f - ram is nonvolatile but operates in other respects as a ram. it provides data retention for 38 years whil e eliminating the reliability concerns, functional disadvantages and system design complexities of battery - backed sram (bbsram). fast write timing and high write endurance make f - ram superior to other types of nonvolatile memory. in - system operation of t he fm 18w08 is very similar to other ram devices. minimum read - and write - cycle times are equal. the f - ram memory, however, is nonvolatile due to its unique ferroelectric memory process. unlike bbsram, the fm 18w08 is a truly monolithic nonvolatile memory. i t provides the same functional benefits of a fast write without the disadvantages associated with modules and batteries or hybrid memory solutions. these capabilities make the fm 18w08 ideal for nonvolatile memory applications requiring frequent or rapid w rites in a bytewide environment. the availability of a true surface - mount package improves the manufacturability of new des igns. device specifications are guaranteed over an industrial temperature range of - 40c to +85c. pin configuration ordering information fm 18w08 - sg 28 - pin green soic a 14 a 12 a 7 a 6 a 5 a 4 a 3 a 2 a 1 a 0 dq 0 dq 1 dq 2 vss dq 3 dq 4 dq 5 dq 6 dq 7 ce a 10 oe a 11 a 9 a 8 a 13 we vdd 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15
fm 18w08 rev. 2.0 dec. 2011 page 2 of 11 figure 1. block diagram pin description pin name type description a(14:0) input address: the 15 address lines select one of 32,768 bytes in the f - ram array. the address value is latched on the falling edge of /ce. dq(7:0) i/o data: 8 - bit bi - directional data bus for accessing the f - ram array. /ce input chip enable: /ce selects the device when low. asserting /ce low causes the address to be latched internally. address change s that occur after /ce goes low will be ignored until the next falling edge occurs. /oe input output enable: asserting /oe low causes the fm 18w08 to drive the data bus when valid data is available. deasserting /oe high causes the dq pins to be tri - stated . /we input write enable: asserting /we low causes the fm 18w08 to write the contents of the data bus to the address location latched by the falling edge of /ce. vdd supply supply voltage vss supply ground functional truth table /ce /we function h x standby/precharge ? x latch address (and begin write if /we=low) l h read l ? write note: the /oe pin controls only the dq output buffers. address latch & decoder a ( 14 : 0 ) ce control logic we a ( 14 : 0 ) i / o latch bus driver oe 32 , 768 x 8 fram array dq ( 7 : 0 )
fm 18w08 rev. 2.0 dec. 2011 page 3 of 11 overview the fm 18w08 is a bytewide f - ram memory. the memory array is logically organized as 32,768 x 8 and is accessed using an ind ustry standard parallel interface. all data written to the part is immediately nonvolatile with no delay. functional operation of the f - ram memory is the same as sram type devices, except the fm 18w08 requires a falling edge of /ce to start each memory cycl e. memory architecture users access 32,768 memory locations each with 8 data bits through a parallel interface. the complete 15 - bit address specifies each of the 32,768 bytes uniquely. internally, the memory array is organized into 4092 rows of 8 - bytes ea ch. this block segmentation has no effect on operation, however the user may wish to group data into blocks by its endurance characteristics as explained on page 4. the cycle time is the same for read and write memory operations. this simplifies memory c ontroller logic and timing circuits. likewise the access time is the same for read and write memory operations. when /ce is deasserted high, a precharge operation begins, and is required of every memory cycle. thus unlike sram, the access and cycle times a re not equal. writes occur immediately at the end of the access with no delay. unlike an eeprom, it is not necessary to poll the device for a ready condition since writes occur at bus speed. it is the users responsibility to ensure that v dd remains wit hin datasheet tolerances to prevent incorrect operation. also proper voltage level and timing relationships between v dd and /ce must be maintained during power - up and power - down events. see power cycle timing diagram on page 9. memory operation the fm 18w08 is designed to operate in a manner similar to other bytewide memory products. for users familiar with bbsram, the performance is comparable but the bytewide interface operates in a slightly different manner as described below. for users familiar with eepr om, the obvious differences result from the higher write performance of f - ram technology including nodelay writes and much higher write endurance. read operation a read operation begins on the falling edge of /ce. at this time, the address bits are latch ed and a memory cycle is initiated. once started, a full memory cycle must be completed internally even if /ce goes inactive. data becomes available on the bus after the access time has been satisfied. after the address has been latched, the address valu e may be changed upon satisfying the hold time parameter. unlike an sram, changing address values will have no effect on the memory operation after the address is latched. the fm 18w08 will drive the data bus when /oe is asserted low. if /oe is asserted a fter the memory access time has been satisfied, the data bus will be driven with valid data. if /oe is asserted prior to completion of the memory access, the data bus will not be driven until valid data is available. this feature minimizes supply current i n the system by eliminating transients caused by invalid data being driven onto the bus. when /oe is inactive the data bus will remain tri - stated. write operation writes occur in the fm 18w08 in the same time interval as reads. the fm 18w08 supports both /c e - and /we - controlled write cycles. in all cases, the address is latched on the falling edge of /ce. in a /ce controlled write, the /we signal is asserted prior to beginning the memory cycle. that is, /we is low when /ce falls. in this case, the part beg ins the memory cycle as a write. the fm 18w08 will not drive the data bus regardless of the state of /oe. in a /we controlled write, the memory cycl e begins on the falling edge of /ce. the /we signal falls after the falling edge of /ce. therefore, the mem ory cycle begins as a read. the data bus will be driven according to the state of /oe until /we falls. the timing of both /ce - and /we - controlled write cycles is shown in the electrical specifications. write access to the array begins asynchronously afte r the memory cycle is initiated. the write access terminates on the rising edge of /we or /ce, whichever is first. data set - up time, as shown in the electrical specifications, indicates the interval during which data cannot change prior to the end of the w rite access. unlike other truly nonvolatile memory technologies, there is no write delay with f - ram . since the read and write access times of the underlying memory are the same, the user experiences no delay through the bus. the entire memory operation o ccurs in a single bus cycle. therefore, any operation including read or write can occur immediately following a write. data polling, a technique used with eeproms to determine if a write is complete, is unnecessary.
fm 18w08 rev. 2.0 dec. 2011 page 4 of 11 precharge operation the precharge opera tion is an internal condition that prepares the memory for a new access. all memory cycles consist of a memory access and a precharge. the precharge is initiated by deasserting the /ce pin high. it must remain high for at least the minimum precharge time t pc . the user determines the beginning of this operation since a precharge will not begin until /ce rises. however, the device has a maximum /ce low time specification that must be satisfied. endurance internally, a f - ram operates with a read and restore mechanism. therefore, each read and write cycle involves a change of state. the memory architecture is based on an array of rows and columns. each read or write access causes an endurance cycle for an entire row. in the fm 18w08 , a row is 64 bits wide. ev ery 8 - byte boundary marks the beginning of a new row. endurance can be optimized by ensuring frequently accessed data is located in different rows. regardless, f - ram offers substantially higher write endurance than other nonvolatile memories. the rated e ndurance limit of 10 14 cycles will allow 150, 0 00 accesses per second to t he same row for over 2 0 years. f - ram design considerations when designing with f - ram for the first time, users of sram will recognize a few minor differences. first, bytewide f - ram me mories latch each address on the falling edge of chip enable. this allows the address bus to change after starting the memory access. since every access latches the memory address on the falling edge of /ce, users cannot ground it as they might with sram. users who are modifying existing designs to use f - ram should examine the memory controller for timing compatibility of address and control pins. each memory access must be qualified with a low transition of /ce. in many cases, this is the only change req uired. an example of the signal relationships is shown in figure 2 below. also shown is a common sram signal relationship that will not work for the fm 18w08 . the reason for /ce to strobe for each address is two - fold: it latches the new address and create s the necessary precharge period while /ce is high. figure 2. chip enable and memory address relationships valid strobing of /ce fram signaling ce address a1 a2 data d1 d2 invalid strobing of /ce sram signaling ce address a1 a2 data d1 d2
fm 18w08 rev. 2.0 dec. 2011 page 5 of 11 a second design consideration relates to the level of v dd during operation. battery - backed srams are forced t o monitor v dd in order to switch to battery backup. they typically block user access below a certain v dd level in order to prevent loading the battery with current demand from an active sram. the user can be abruptly cut off from access to the nonvolatile memory in a power down situation with no warning or indication. f - ram memories do not need this system overhead. the memory will not block access at any v dd level that complies with the specified operating range. the user should take measures to prevent the processor from accessing memory when v dd is out - of - tolerance. the common design practice of holding a processor in reset during powerdown may be sufficient. it is recommended that chip enable is pulled high and allowed to track v dd during powerup and powerdown cycles. it is the users responsibility to ensure that chip enable is hig h to prevent accesses below v dd min . ( 2.7 v). figure 3 shows a pullup resistor on /ce which will keep the pin high during power cycles assuming the mcu/mpu pin tri - states during the reset condition. the pullup resistor value should be chosen to ensure the /ce pin tracks v dd yet a high enough value that the current drawn when /ce is low is not an issue. figure 3. use of pullup resistor on /ce ce we oe a(14:0) dq fm 18w08 v dd mcu/ mpu r
fm 18w08 rev. 2.0 dec. 2011 page 6 of 11 electrical specifications absolute maximum ratings symbol description ratings v dd power supply voltage with respect to v ss - 1.0v to +7.0v v in voltage on any pin with respect to v ss - 1.0v to +7.0v and v in < v dd +1.0v t stg storage temperature - 55 ? c to + 125 ? c t lead lead temperature (soldering, 10 seconds) 26 0 ? c v esd electrostatic discharge voltage - human body model (aec - q100 - 002 rev. e) - charged device model (aec - q100 - 011 rev. b) - machine model ( a ec - q100 - 003 rev. e ) 4kv 1.25kv 300v packa ge moisture sensitivity level msl - 2 stresses above those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating only, and the functional operation of the device at these or any other conditions above thos e listed in the operational section of this specification is not implied. exposure to absolute maximum ratings conditions for extended periods may affect device reliabil ity. dc operating conditions ( t a = - 40 ? c to + 85 ? c, v dd = 2.7 v to 5.5v unless otherw ise specified) symbol parameter min typ max units notes v dd power supply 2.7 3.3 5.5 v i dd v dd supply current - 12 ma 1 i sb standby current 20 5 0 ? a 2 i li input leakage current - ? 1 ? a 3 i lo output leakage current - ? 1 ? a 3 v ih input high volta ge 0.7*v dd v dd +0.3 v v il input low voltage - 0.3 0.3*v dd v v oh1 output high voltage ( i oh = - 1 ma, v dd =2.7v) 2.4 v v oh2 output high voltage ( i oh = - 100 ? a) v dd - 0.2 v v ol1 output low voltage ( i ol = 2 ma, v dd =2.7v) 0.4 v v ol2 output low volta ge ( i ol = 150 ? a) 0.2 v notes 1. v dd = 5.5v, /ce cycling at minimum cycle time. all inputs at cmos levels, all outputs unloaded. 2. /ce at v ih , all other pins at cmos levels (0.2v or v dd - 0.2v) . 3. v in , v out between v dd and v ss .
fm 18w08 rev. 2.0 dec. 2011 page 7 of 11 read cycle ac parameters ( t a = - 40 ? c to + 85 ? c, c l = 30 pf, unless otherwise specified) v dd 2.7 to 3.0v v dd 3.0 to 5.5v symbol parameter min max min max units notes t ce chip enable access time (to data valid) 80 70 ns t ca chip enable active time 80 70 ns t rc read cycl e time 145 130 ns t pc precharge time 65 60 ns t as address setup time 0 0 ns t ah address hold time 15 15 ns t oe output enable access time 15 12 ns t hz chip enable to output high - z 15 15 ns 1 t ohz output enable to output high - z 15 15 ns 1 write cycle ac parameters (t a = - 40 ? c to + 85 ? c, unless otherwise specified) v dd 2.7 to 3.0v v dd 3.0 to 5.5v symbol parameter min max min max units notes t ca chip enable active time 80 70 ns t cw chip enable to write high 80 70 ns t wc write cycle time 145 130 ns t pc precharge time 65 60 ns t as address setup time 0 0 ns t ah address hold time 15 15 ns t wp write enable pulse width 50 40 ns t ds data setup 40 30 ns t dh data hold 0 0 ns t wz write enable low to out put high z 15 15 ns 1 t wx write enable high to output driven 10 10 ns 1 t hz chip enable to output high - z 15 15 ns 1 t ws write enable setup 0 0 ns 2 t wh write enable hold 0 0 ns 2 notes 1 t his parameter is periodically sampled and not 100% test ed . 2 the relationship between /ce and /we determines if a /ce - or /we - controlled write occurs. there is no timing specification associated with this relationship. data retention symbol parameter min max units notes t dr @ +85oc 10 - years @ +80oc 1 9 - years @ +75oc 38 - years
fm 18w08 rev. 2.0 dec. 2011 page 8 of 11 capacitance ( t a = 25 ? c, f=1.0 mhz, v dd = 5v) symbol parameter min max units notes c i/o input/ output capacitance (dq) - 8 pf c in input capacitance - 6 pf ac test co nditions input pulse levels 10% and 90% of v dd input rise and fall times 5 ns input and output timing levels 0.5 v dd read cycle timing write cycle timing - /ce controlled timing equivalent ac load circuit ce a0-14 oe dq0-7 t as t ah t ce t oe t ca t rc t pc t ohz t hz ce a0-14 we dq0-7 t as t ah t ca t wc t pc oe t ws t ds t dh t wh
fm 18w08 rev. 2.0 dec. 2011 page 9 of 11 write c ycle timing - /we controlled timing power cycle timing power cycle timing (t a = - 40 ? c to + 85 ? c, v dd = 2.7v to 5.5v unless otherwise specified) symbol parameter min max units notes t pu v dd (min) to first access s tart 1 0 - m s t pd last access complete to v dd (min) 0 - ? s t v r v dd rise time 3 0 - ? s/v 1 t vf v dd fall time 10 0 - ? s/v 1 notes 1. sl ope measured at any point on v dd waveform . ce a0-14 we dq0-7 out t as t ah t ca t wc t pc oe t ws t wh dq0-7 in t ds t wp t wz t wx t dh t c w v ih (min) t pd t pu v dd ce v il (max) v dd (min) t pc v dd (min) v ih (min) v ih (min) v ih (min) t pd t pd t pu t pu v dd ce v il (max) v il (max) v dd (min) v dd (min) t pc t pc v dd (min) v dd (min) v ih (min) v ih (min)
fm 18w08 rev. 2.0 dec. 2011 page 10 of 11 28 - pin soic (jedec ms - 013 variation ae) all dimensions in millimeters soic package marking scheme legend: xx xx xx= part number, p= package type ( - s g) r= rev code, yy=year, ww=work week, llllll = lot code example: fm 18w08 , 70ns speed, green /rohs soic package, a die rev. , year 2010, work week 37 , lot code 00002g ramtron fm 18w08 - s g a103700002g ramtron xxxx xxx - p r yyww ll l ll l pin 1 7 . 50 0 . 10 10 . 30 0 . 30 17 . 90 0 . 20 0 . 10 0 . 30 2 . 35 2 . 65 0 . 33 0 . 51 1 . 27 typ 0 . 10 0 . 25 0 . 75 45 ? 0 . 40 1 . 27 0 . 23 0 . 32 0 ? - 8 ?
fm 18w08 rev. 2.0 dec. 2011 page 11 of 11 revision history revision date summary 1.0 11/ 22 /2010 initial release 1.1 12/20 /2010 updated msl rating. 1.2 3/10 /2011 changed t pu and t vf spec limits. 2.0 12/20/2011 changed to pre - production status.

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