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FM1608
64Kb Bytewide FRAM Memory
Features
64K bit Ferroelectric Nonvolatile RAM * Organized as 8,192 x 8 bits * High Endurance 1 Trillion (1012) Read/Writes * 10 year Data Retention * NoDelayTM Writes * Advanced High-Reliability Ferroelectric Process 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 8Kx8 SRAM & EEPROM pinout * 120 ns Access Time * 180 ns Cycle Time Low Power Operation * 15 mA Active Current * 20 A Standby Current Industry Standard Configuration * Industrial Temperature -40 C to +85 C * 28-pin SOIC or DIP * "Green" Packaging Options
Description
The FM1608 is a 64-kilobit nonvolatile memory employing an advanced ferroelectric process. A ferroelectric random access memory or FRAM is nonvolatile but operates in other respects as a RAM. It provides data retention for 10 years while eliminating the reliability concerns, functional disadvantages and system design complexities of battery-backed SRAM. Its fast write and high write endurance make it superior to other types of nonvolatile memory. In-system operation of the FM1608 is very similar to other RAM based devices. Minimum read- and writecycle times are equal. The FRAM memory, however, is nonvolatile due to its unique ferroelectric memory process. Unlike BBSRAM, the FM1608 is a truly monolithic nonvolatile memory. It provides the same functional benefits of a fast write without the serious disadvantages associated with modules and batteries or hybrid memory solutions. These capabilities make the FM1608 ideal for nonvolatile memory applications requiring frequent or rapid writes in a bytewide environment. The availability of a true surface-mount package improves the manufacturability of new designs, while the DIP package facilitates simple design retrofits. The FM1608 offers guaranteed operation over an industrial temperature range of -40C to +85C.
Pin Configuration
NC A12 A7 A6 A5 A4 A3 A2 A1 A0 DQ0 DQ1 DQ2 VSS
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
VDD WE NC A8 A9 A11 OE A10 CE DQ7 DQ6 DQ5 DQ4 DQ3
FM1608-120-P FM1608-120-S FM1608-120-PG FM1608-120-SG
Ordering Information 120 ns access, 28-pin plastic DIP 120 ns access, 28-pin SOIC 120 ns access, 28-pin "Green" DIP 120 ns access, 28-pin "Green" SOIC
This product conforms to specifications per the terms of the Ramtron standard warranty. The product has completed Ramtron's internal qualification testing and has reached production status. Rev 3.0
Ramtron International Corporation 1850 Ramtron Drive, Colorado Springs, CO 80921 (800) 545-FRAM, (719) 481-7000 http://www.ramtron.com
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FM1608
A10-A12
Block Decoder
A0-A12
Address Latch
A0-A7
Row Decoder
8,192 x 8 FRAM Array
CE
A8-A9
Column Decoder
WE OE
Control Logic
I/O Latch Bus Driver
DQ0-7
Figure 1. Block Diagram
Pin Description Pin Name A0-A12 DQ0-7 /CE I/O Input I/O Input Pin Description Address: The 13 address inputs select one of 8,192 bytes in the FRAM array. The address value will be latched on the falling edge of /CE. Data: 8-bit bi-directional data bus for accessing the FRAM array. Chip Enable: /CE selects the device when low. Asserting /CE low causes the address to be latched internally. Address changes that occur after /CE goes low will be ignored until the next falling edge occurs. Output Enable: Asserting /OE low causes the FM1608 to drive the data bus when valid data is available. Deasserting /OE high causes the DQ pins to be tri-stated. Write Enable: Asserting /WE low causes the FM1608 to write the contents of the data bus to the address location latched by the falling edge of /CE. Supply Voltage: 5V Ground.
/OE /WE VDD VSS
Input Input Supply Supply
Functional Truth Table /CE /WE H X X L H L
Function Standby/Precharge Latch Address (and Begin Write if /WE=low) Read Write
Note: The /OE pin controls only the DQ output buffers.
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FM1608
Overview
The FM1608 is a bytewide FRAM memory. The memory array is logically organized as 8,192 x 8 and is accessed using an industry standard parallel interface. The FM1608 is inherently nonvolatile via its unique ferroelectric process. All data written to the part is immediately nonvolatile with no delay. Functional operation of the FRAM memory is the same as SRAM type devices, except the FM1608 requires a falling edge of /CE to start each memory cycle. of FRAM 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 latched and a memory cycle is initiated. Once started, a complete memory cycle must be completed internally regardless of the state of /CE. Data becomes available on the bus after the access time has been satisfied. After the address has been latched, the address value may change 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 FM1608 will drive the data bus when /OE is asserted low. If /OE is asserted after 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 in 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 FM1608 within the same time interval as reads. The FM1608 supports both /CEand /WE-controlled write cycles. In both 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 begins the memory cycle as a write. The FM1608 will not drive the data bus regardless of the state of /OE. In a /WE-controlled write, the memory cycle begins on the falling edge of /CE. The /WE signal falls after the falling edge of /CE. Therefore the memory 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 section. Write access to the array begins asynchronously after 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 write access.
Memory Architecture
Users access 8,192 memory locations each with 8 data bits through a parallel interface. The 13-bit address specifies each of the 8,192 bytes uniquely. Internally, the memory array is organized into 8 blocks of 1Kb each. The 3 most-significant address inputs decode one of 8 blocks. This block segmentation has no effect on operation, however the user may wish to group data into blocks by its endurance requirements as explained in a later section. The cycle time is the same for read and write memory operations. This simplifies memory controller 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 are 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. Note that the FM1608 has no special power-down demands. It will not block user access, and it contains no power-management circuits other than a simple internal power-on reset. It is the user's responsibility to ensure that VDD is within datasheet tolerances and to ensure the proper voltage level and timing relationship between VDD and /CE in power-up and power-down events to prevent incorrect operation.
Memory Operation
The FM1608 is designed to operate in a manner very 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 EEPROM, the obvious differences result from the higher write performance
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FM1608 Unlike other truly nonvolatile memory technologies, there is no write delay with FRAM. 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 occurs 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. Precharge Operation The precharge operation 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 tPC. The user dictates 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
The FM1608 internally 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 FM1608, a row is 32 bits wide. Every 4-byte boundary marks the beginning of a new row. Endurance can be optimized by ensuring frequently accessed data is located in different rows. Regardless, FRAM offers substantially higher write endurance than other nonvolatile memories. The rated endurance limit of 1012 cycles will allow 3000 accesses per second to the same row for 10 years.
Applications
As the first truly nonvolatile RAM, the FM1608 fits into many diverse applications. Clearly, its monolithic nature and high performance make it superior to battery-backed SRAM in most every application. The advantages of FRAM memory compared with batterybacked SRAM include its immunity to humidity and shock. Also FRAM is lower cost, has a smaller board footprint, and eliminates the battery - a source of environmental and field replacement concerns. The FRAM Design Considerations section that follows highlights the simple design considerations that should be reviewed in both retrofit and new design situations.
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FM1608 FRAM Design Considerations When designing with FRAM for the first time, users of SRAM will recognize a few minor differences. First, bytewide FRAM memories 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 FRAM 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 required. 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 FM1608. The reason for /CE to strobe for each address is twofold: it latches the new address and creates the necessary precharge period while /CE is high. A second design consideration relates to the level of VDD during operation. Battery-backed SRAMs are designed to monitor VDD in order to switch to battery backup. They typically block user access below a certain VDD level in order to minimize battery drain from an otherwise active SRAM. The user can be abruptly cut off from access to the memory in a power down situation without warning. FRAM memories do not need this system overhead. The memory will not block access at any VDD level. The user, however, should prevent the processor from accessing memory when VDD is out-of-tolerance. Check the min/max VDD specifications on FRAM datasheet. The common design practice of holding a processor in reset when VDD drops is sufficient. No special provisions must be taken for FRAM design.
Figure 2. Memory Address and /CE Relationships
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FM1608
Electrical Specifications
Absolute Maximum Ratings Symbol Description VDD Power Supply Voltage with respect to VSS VIN Voltage on any pin with respect to VSS TSTG TLEAD Storage Temperature Lead temperature (Soldering, 10 seconds) Ratings -1.0V to +7.0V -1.0V to +7.0V and VIN < VDD+1.0V -55C to + 125C 300 C
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 those listed in the operational section of this specification is not implied. Exposure to absolute maximum ratings conditions for extended periods may affect device reliability.
DC Operating Conditions (TA = -40 C to + 85 C, VDD = 4.5V to 5.5V unless otherwise specified) Symbol Parameter Min Typ Max Units VDD Power Supply 4.5 5.0 5.5 V IDD1 VDD Supply Current - Active 5 15 mA ISB1 Standby Current - TTL 400 A ISB2 Standby Current - CMOS 7 20 A ILI Input Leakage Current 10 A ILO Output Leakage Current 10 A VIH Input High Voltage 2.0 VDD + 0.3 V VIL Input Low Voltage -0.3 0.8 V VOH Output High Voltage (IOH = -2.0 mA) 2.4 V VOL Output Low Voltage (IOL = -4.2 mA) 0.4 V Notes 1. VDD = 5.5V, /CE cycling at minimum cycle time. All inputs at CMOS levels, all outputs unloaded. 2. VDD = 5.5V, /CE at VIH, All other pins at TTL levels. 3. VDD = 5.5V, /CE at VIH, All other pins at CMOS levels. 4. VIN, VOUT between VDD and VSS.
Notes 1 2 3 4 4
Data Retention (VDD = 4.5V to 5.5V unless otherwise specified) Parameter Min Units Data Retention 10 Years
Notes
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FM1608 Read Cycle AC Parameters (TA = -40 C to + 85 C, VDD = 4.5V to 5.5V unless otherwise specified) Symbol Parameter Min Max Units tCE Chip Enable Access Time ( to data valid) 120 ns tCA Chip Enable Active Time 120 2,000 ns tRC Read Cycle Time 180 ns tPC Precharge Time 60 ns tAS Address Setup Time 0 ns tAH Address Hold Time 10 ns tOE Output Enable Access Time 10 ns tHZ Chip Enable to Output High-Z 15 ns tOHZ Output Enable to Output High-Z 15 ns Write Cycle AC Parameters (TA = -40 C to + 85 C, VDD = 4.5V to 5.5V unless otherwise specified) Symbol Parameter Min Max Units tCA Chip Enable Active Time 120 2,000 ns tCW Chip Enable to Write High 120 ns tWC Write Cycle Time 180 ns tPC Precharge Time 60 ns tAS Address Setup Time 0 ns tAH Address Hold Time 10 ns tWP Write Enable Pulse Width 40 ns tDS Data Setup 40 ns tDH Data Hold 0 ns tWZ Write Enable Low to Output High Z 15 ns tWX Write Enable High to Output Driven 10 ns tHZ Chip Enable to Output High-Z 15 ns tWS Write Setup 0 ns tWH Write Hold 0 ns Notes
1 2
Notes
1 1
Notes
1 1 1 2 2
This parameter is periodically sampled and not 100% tested. The relationship between /CE and /WE determines if a /CE- or /WE-controlled write occurs. There is no timing specification associated with this relationship.
Power Cycle Timing (TA = -40 C to + 85 C, VDD = 4.5V to 5.5V unless otherwise specified) Symbol Parameter Min Max Units tPU VDD(min) to First Access Start 1 S tPD Last Access Complete to VDD(min) 0 S
Notes
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FM1608 Capacitance (TA = 25 C , f=1.0 MHz, VDD = 5V) Symbol Parameter Max CI/O Input Output Capacitance 8 CIN Input Capacitance 6 AC Test Conditions Input Pulse Levels Input rise and fall times Input and output timing levels
Units pF pF
Notes
Equivalent AC Load Circuit 0 to 3V 10 ns 1.5V
Read Cycle Timing
/CE-Controlled Write Cycle Timing
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FM1608
/WE-Controlled Write Cycle Timing
Power Cycle Timing
VDD (min) t PD t PC VDD (min) t PU VIH (min) VIL (max)
VDD
CE
VIH (min)
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FM1608 28-pin SOIC (JEDEC MS-013 variation AE)
E
H
Pin 1
D A e B A1 .10 mm .004 in. h 45
L C
Selected Dimensions For complete dimensions and notes, refer to JEDEC MS-013 Controlling dimensions in millimeters. Conversions to inches are not exact. Symbol A A1 B C D E e H h L
Dim mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in.
Min 2.35 0.0926 0.10 0.004 0.33 0.013 0.23 0.0091 17.70 0.6969 7.40 0.2914
Nom.
Max 2.65 0.1043 0.30 0.0118 0.51 0.020 0.32 0.0125 18.10 0.7125 7.60 0.2992
1.27 BSC 0.050 BSC 10.00 0.394 0.25 0.010 .40 0.016 0 10.65 0.419 0.75 0.029 1.27 0.050 8
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FM1608 28-pin DIP JEDEC MS-011
E1 PIN 1 D E A2 A A1 D1 e eA eB
B1
B
L
Selected Dimensions For complete dimensions and notes, refer to JEDEC MS-011 Controlling dimensions in inches. Conversions to millimeters are not exact. Symbol A A1 A2 B B1 D D1 E E1 e eA eB L Units in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm Min. Nom. Max. 0.250 6.35
0.015 0.39 0.125 3.18 0.014 0.356 0.030 0.77 1.380 35.1 0.005 0.13 0.600 15.24 0.485 12.32 0.100 BSC 2.54 BSC 0.600 BSC 15.24 BSC
0.195 4.95 0.022 0.558 0.070 1.77 1.565 39.7
0.625 15.87 0.580 14.73
0.115 2.93
0.700 17.78 0.200 5.08
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