Preliminary FM24CL32 32Kb Serial 3V F-RAM Memory Features 32K bit Ferroelectric Nonvolatile RAM • Organized as 4,096 x 8 bits • Unlimited Read/Write Cycles • 45 year Data Retention • NoDelay™ Writes • Advanced High-Reliability Ferroelectric Process Fast Two-wire Serial Interface • Up to 1 MHz maximum bus frequency • Direct hardware replacement for EEPROM • Supports legacy timing for 100 kHz & 400 kHz Description The FM24CL32 is a 32-kilobit nonvolatile memory employing an advanced ferroelectric process. A ferroelectric random access memory or F-RAM is nonvolatile and performs reads and writes like a RAM. It provides reliable data retention for 45 years while eliminating the complexities, overhead, and system level reliability problems caused by EEPROM and other nonvolatile memories. The FM24CL32 performs write operations at bus speed. No write delays are incurred. The next bus cycle may commence immediately without the need for data polling. In addition, the product offers write endurance orders of magnitude higher than EEPROM. Also, F-RAM exhibits much lower power during writes than EEPROM since write operations do not require an internally elevated power supply voltage for write circuits. These capabilities make the FM24CL32 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 EEPROM can cause data loss. The combination of features allows more frequent data writing with less overhead for the system. Low Power Operation • True 2.7V-3.6V Operation • 70 µA Active Current (100 kHz) • 12 µA Standby Current Industry Standard Configuration • Industrial Temperature -40° C to +85° C • 8-pin “Green”/RoHS SOIC Package Pin Configuration A0 A1 A2 1 8 2 7 3 6 VSS 4 5 Pin Names A0-A2 SDA SCL WP VSS VDD VDD WP SCL SDA Function Device Select Address Serial Data/address Serial Clock Write Protect Ground Supply Voltage Ordering Information FM24CL32-G FM24CL32-GTR “Green”/RoHS 8-pin SOIC “Green”/RoHS 8-pin SOIC, Tape & Reel The FM24CL32 provides substantial benefits to users of serial EEPROM, yet these benefits are available in a hardware drop-in replacement. The FM24CL32 is available in an industry standard 8-pin SOIC package using a familiar two-wire protocol. It is guaranteed over an industrial temperature range of -40°C to +85°C. This is a product that has fixed target specifications but are subject to change pending characterization results. Rev. 1.0 May 2009 Ramtron International Corporation 1850 Ramtron Drive, Colorado Springs, CO 80921 (800) 545-FRAM, (719) 481-7000 http://www.ramtron.com Page 1 of 12 FM24CL32 Counter Address Latch 1,024 x 32 FRAM Array 8 SDA Serial to Parallel Converter Data Latch SCL WP Control Logic A0-A2 Figure 1. FM24CL32 Block Diagram Pin Description Pin Name A0-A2 Type Input SDA I/O SCL Input WP Input VDD VSS Rev. 1.0 May 2009 Supply Supply Pin Description Address 0-2. These pins are used to select one of up to 8 devices of the same type on the same two-wire bus. To select the device, the address value on the three pins must match the corresponding bits contained in the device address. The address pins are pulled down internally. Serial Data Address. This is a bi-directional line for the two-wire interface. It is open-drain and is intended to be wire-OR’d with other devices on the two-wire bus. The input buffer incorporates a Schmitt trigger for noise immunity and the output driver includes slope control for falling edges. A pull-up resistor is required. Serial Clock. The serial clock line for the two-wire interface. Data is clocked out of the part on the falling edge, and in on the rising edge. The SCL input also incorporates a Schmitt trigger input for noise immunity. Write Protect. When tied to VDD, addresses in the entire memory map will be writeprotected. When WP is connected to ground, all addresses may be written. This pin is pulled down internally. Supply Voltage: 2.7V to 3.6V Ground Page 2 of 12 FM24CL32 Overview Two-wire Interface The FM24CL32 is a serial F-RAM memory. The memory array is logically organized as a 4,096 x 8 bit memory array and is accessed using an industry standard two-wire interface. Functional operation of the F-RAM is similar to serial EEPROMs. The major difference between the FM24CL32 and a serial EEPROM with the same pinout relates to its superior write performance. The FM24CL32 employs a bi-directional two-wire bus protocol using few pins or board space. Figure 2 illustrates a typical system configuration using the FM24CL32 in a microcontroller-based system. The industry standard two-wire bus is familiar to many users but is described in this section. Memory Architecture When accessing the FM24CL32, the user addresses 4,096 locations each with 8 data bits. These data bits are shifted serially. The 4,096 addresses are accessed using the two-wire protocol, which includes a slave address (to distinguish other non-memory devices), and an extended 16-bit address. Only the lower 12 bits are used by the decoder for accessing the memory. The upper four address bits should be set to 0 for compatibility with larger devices in the future. The access time for 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 two-wire bus. Unlike an EEPROM, it is not necessary to poll the device for a ready condition since writes occur at bus speed. That is, by the time a new bus transaction can be shifted into the part, a write operation will be complete. This is explained in more detail in the interface section below. Users expect several obvious system benefits from the FM24CL32 due to its fast write cycle and high endurance as compared with EEPROM. However there are less obvious benefits as well. For example in a high noise environment, the fast-write operation is less susceptible to corruption than an EEPROM since it is completed quickly. By contrast, an EEPROM requiring milliseconds to write is vulnerable to noise during much of the cycle. By convention, any device that is sending data onto the bus is the transmitter while the target device for this data is the receiver. The device that is controlling the bus is the master. The master is responsible for generating the clock signal for all operations. Any device on the bus that is being controlled is a slave. The FM24CL32 always is a slave device. The bus protocol is controlled by transition states in the SDA and SCL signals. There are four conditions including start, stop, data bit, or acknowledge. Figure 3 illustrates the signal conditions that specify the four states. Detailed timing diagrams are in the electrical specifications. VDD Rmin = 1.1 K? Rmax = tR/Cbus Microcontroller SDA SCL SDA SCL FM24CL32 FM24CL32 A0 A1 A2 A0 A1 A2 Figure 2. Typical System Configuration Note that it is the user’s responsibility to ensure that VDD is within datasheet tolerances to prevent incorrect operation. Rev. 1.0 May 2009 Page 3 of 12 FM24CL32 SCL 7 SDA Stop (Master) Start (Master) 6 Data bits (Transmitter) 0 Data bit Acknowledge (Transmitter) (Receiver) Figure 3. Data Transfer Protocol Stop Condition A stop condition is indicated when the bus master drives SDA from low to high while the SCL signal is high. All operations using the FM24CL32 should end with a stop condition. If an operation is in progress when a stop is asserted, the operation will be aborted. The master must have control of SDA (not a memory read) in order to assert a stop condition. Start Condition A start condition is indicated when the bus master drives SDA from high to low while the SCL signal is high. All commands should be preceded by a start condition. An operation in progress can be aborted by asserting a start condition at any time. Aborting an operation using the start condition will ready the FM24CL32 for a new operation. If during operation the power supply drops below the specified VDD minimum, the system should issue a start condition prior to performing another operation. Data/Address Transfer All data transfers (including addresses) take place while the SCL signal is high. Except under the two conditions described above, the SDA signal should not change while SCL is high. Acknowledge The acknowledge takes place after the 8th data bit has been transferred in any transaction. During this state the transmitter should release the SDA bus to allow the receiver to drive it. The receiver drives the SDA signal low to acknowledge receipt of the byte. If the receiver does not drive SDA low, the condition is a no-acknowledge and the operation is aborted. Second and most common, the receiver does not acknowledge to deliberately end an operation. For example, during a read operation, the FM24CL32 will continue to place data onto the bus as long as the receiver sends acknowledges (and clocks). When a read operation is complete and no more data is needed, the receiver must not acknowledge the last byte. If the receiver acknowledges the last byte, this will cause the FM24CL32 to attempt to drive the bus on the next clock while the master is sending a new command such as stop. Slave Address The first byte that the FM24CL32 expects after a start condition is the slave address. As shown in Figure 4, the slave address contains the device type, the device select address bits, and a bit that specifies if the transaction is a read or a write. Bits 7-4 are the device type and should be set to 1010b for the FM24CL32. These bits allow other types of function types to reside on the 2-wire bus within an identical address range. Bits 3-1 are the address select bits. They must match the corresponding value on the external address pins to select the device. Up to eight FM24CL32s can reside on the same two-wire bus by assigning a different address to each. Bit 0 is the read/write bit. R/W=1 indicates a read operation and R/W=0 indicates a write operation. The receiver would fail to acknowledge for two distinct reasons. First is that a byte transfer fails. In this case, the no-acknowledge ceases the current operation so that the part can be addressed again. This allows the last byte to be recovered in the event of a communication error. Rev. 1.0 May 2009 Page 4 of 12 FM24CL32 Memory Operation Device Select Slave ID 1 0 1 0 A2 A1 A0 R/W 7 6 5 4 3 2 1 0 Figure 4. Slave Address Addressing Overview After the FM24CL32 (as receiver) acknowledges the device address, the master can place the memory address on the bus for a write operation. The address requires two bytes. The first is the MSB. Since the device uses only 12 address bits, the value of the upper four bits are “don’t care”. Following the MSB is the LSB with the remaining eight address bits. The address value is latched internally. Each access causes the latched address value to be incremented automatically. The current address is the value that is held in the latch -- either a newly written value or the address following the last access. The current address will be held for as long as power remains or until a new value is written. Reads always use the current address. A random read address can be loaded by beginning a write operation as explained below. After transmission of each data byte, just prior to the acknowledge, the FM24CL32 increments the internal address latch. This allows the next sequential byte to be accessed with no additional addressing. After the last address (FFFh) is reached, the address latch will roll over to 0000h. There is no limit to the number of bytes that can be accessed with a single read or write operation. Data Transfer After the address information has been transmitted, data transfer between the bus master and the FM24CL32 can begin. For a read operation the FM24CL32 will place 8 data bits on the bus then wait for an acknowledge from the master. If the acknowledge occurs, the FM24CL32 will transfer the next sequential byte. If the acknowledge is not sent, the FM24CL32 will end the read operation. For a write operation, the FM24CL32 will accept 8 data bits from the master then send an acknowledge. All data transfer occurs MSB (most significant bit) first. The FM24CL32 is designed to operate in a manner very similar to other 2-wire interface memory products. The major differences result from the higher performance write capability of F-RAM technology. These improvements result in some differences between the FM24CL32 and a similar configuration EEPROM during writes. The complete operation for both writes and reads is explained below. Write Operation All writes begin with a device address, then a memory address. The bus master indicates a write operation by setting the LSB of the device address to a 0. After addressing, the bus master sends each byte of data to the memory and the memory generates an acknowledge condition. Any number of sequential bytes may be written. If the end of the address range is reached internally, the address counter will wrap from FFFh to 0000h. Unlike other nonvolatile memory technologies, there is no effective 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 cycle occurs in less time than a single bus clock. Therefore, any operation including read or write can occur immediately following a write. Acknowledge polling, a technique used with EEPROMs to determine if a write is complete is unnecessary and will always return a ready condition. Internally, an actual memory write occurs after the 8th data bit is transferred. It will be complete before the acknowledge is sent. Therefore, if the user desires to abort a write without altering the memory contents, this should be done using start or stop condition prior to the 8th data bit. The FM24CL32 uses no page buffering. The memory array can be write protected using the WP pin. Setting the WP pin to a high condition (VDD) will write-protect all addresses. The FM24CL32 will not acknowledge data bytes that are written to protected addresses. In addition, the address counter will not increment if writes are attempted to these addresses. Setting WP to a low state (VSS) will deactivate this feature. WP is pulled down internally. Figure 5 below illustrates both a single-byte and multiple-write. Rev. 1.0 May 2009 Page 5 of 12 FM24CL32 Start By Master S Stop Address & Data Slave Address 0 A Address MSB By FM24CL32 A Address LSB A Data Byte A P Acknowledge Figure 5. Single Byte Write Start S By FM24CL32 Stop Address & Data By Master Slave Address 0 A Address MSB A Address LSB A Data Byte A Data Byte A P Acknowledge Figure 6. Multiple Byte Write Read Operation There are two basic types of read operations. They are current address read and selective address read. In a current address read, the FM24CL32 uses the internal address latch to supply the address. In a selective read, the user performs a procedure to set the address to a specific value. Current Address & Sequential Read As mentioned above the FM24CL32 uses an internal latch to supply the address for a read operation. A current address read uses the existing value in the address latch as a starting place for the read operation. The system reads from the address immediately following that of the last operation. To perform a current address read, the bus master supplies a device address with the LSB set to 1. This indicates that a read operation is requested. After receiving the complete device address, the FM24CL32 will begin shifting out data from the current address on the next clock. The current address is the value held in the internal address latch. Beginning with the current address, the bus master can read any number of bytes. Thus, a sequential read is simply a current address read with multiple byte transfers. After each byte the internal address counter will be incremented. Each time the bus master acknowledges a byte, this indicates that the FM24CL32 should read out the next sequential byte. Rev. 1.0 May 2009 There are four ways to properly terminate a read operation. Failing to properly terminate the read will most likely create a bus contention as the FM24CL32 attempts to read out additional data onto the bus. The four valid methods are: 1. 2. 3. 4. The bus master issues a no-acknowledge in the 9th clock cycle and a stop in the 10th clock cycle. This is illustrated in the diagrams below. This is preferred. The bus master issues a no-acknowledge in the 9th clock cycle and a start in the 10th. The bus master issues a stop in the 9th clock cycle. The bus master issues a start in the 9th clock cycle. If the internal address reaches FFFh, it will wrap around to 0000h on the next read cycle. Figures 7 and 8 below show the proper operation for current address reads. Selective (Random) Read There is a simple technique that allows a user to select a random address location as the starting point for a read operation. This involves using the first three bytes of a write operation to set the internal address followed by subsequent read operations. To perform a selective read, the bus master sends out the device address with the LSB set to 0. This specifies a write operation. According to the write protocol, the bus master then sends the address bytes that are loaded into the internal address latch. After the FM24CL32 acknowledges the address, the bus Page 6 of 12 FM24CL32 set to a 1. The operation is now a current address read. master issues a start condition. This simultaneously aborts the write operation and allows the read command to be issued with the device address LSB By Master Start No Acknowledge Address Stop S Slave Address By FM24CL32 1 A Acknowledge Data Byte 1 P Data Figure 7. Current Address Read Start By Master Address No Acknowledge Acknowledge Stop S Slave Address By FM24CL32 1 A Data Byte A Acknowledge Data Byte 1 P Data Figure 8. Sequential Read Start Address By Master Start No Acknowledge Address Stop S By FM24CL32 Slave Address 0 A Address MSB A Address LSB A S Slave Address Acknowledge 1 A Data Byte 1 P Data Figure 9. Selective (Random) Read Rev. 1.0 May 2009 Page 7 of 12 FM24CL32 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 VESD Storage Temperature Lead Temperature (Soldering, 10 seconds) Electrostatic Discharge Voltage - Human Body Model (JEDEC Std JESD22-A114-B) - Machine Model (JEDEC Std JESD22-A115-A) Package Moisture Sensitivity Level Ratings -1.0V to +5.0V -1.0V to +5.0V and VIN < VDD+1.0V * -55°C to +125°C 300° C TBD TBD MSL-1 * Exception: The “VIN < VDD+1.0V” restriction does not apply to the SCL and SDA inputs. 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 =2.7V to 3.6V unless otherwise specified) Symbol Parameter Min Typ Max Units VDD Main Power Supply 2.7 3.6 V IDD VDD Supply Current @ SCL = 100 kHz 70 µA @ SCL = 400 kHz 250 µA @ SCL = 1 MHz 600 µA ISB Standby Current 12 µA ILI Input Leakage Current ±1 µA ILO Output Leakage Current ±1 µA VIL Input Low Voltage -0.3 0.3 VDD V VIH Input High Voltage 0.7 VDD VDD + 0.5 V VOL Output Low Voltage 0.4 V @ IOL = 3.0 mA RIN Address Input Resistance (WP, A2-A0) 50 For VIN = VIL (max) KΩ 1 For VIN = VIH (min) MΩ VHYS Input Hysteresis 0.05 VDD V Notes 1 2 3 3 5 4 Notes 1. SCL toggling between VDD-0.3V and VSS, other inputs VSS or VDD-0.3V. 2. SCL = SDA = VDD. WP = A0 = A1 = A2 = VSS. Stop command issued. 3. VIN or VOUT = VSS to VDD. Does not apply to WP, A2-A0 pins. 4. This parameter is characterized but not tested. 5. The input pull-down circuit is strong (50KΩ) when the input voltage is below VIL and weak (1MΩ) when the input voltage is above VIH. Rev. 1.0 May 2009 Page 8 of 12 FM24CL32 AC Parameters (TA = -40° C to + 85° C, VDD =2.7V to 3.6V unless otherwise specified) Symbol Parameter Min Max Min Max Min Max fSCL SCL Clock Frequency 0 100 0 400 0 1000 tLOW Clock Low Period 4.7 1.3 0.6 tHIGH Clock High Period 4.0 0.6 0.4 tAA SCL Low to SDA Data Out Valid 3 0.9 0.55 tBUF tHD:STA tSU:STA tHD:DAT tSU:DAT tR tF tSU:STO tDH tSP Bus Free Before New Transmission Start Condition Hold Time Start Condition Setup for Repeated Start Data In Hold Data In Setup Input Rise Time Input Fall Time Stop Condition Setup Data Output Hold (from SCL @ VIL) Noise Suppression Time Constant on SCL, SDA Units kHz µs µs µs 4.7 1.3 0.5 µs 4.0 4.7 0.6 0.6 0.25 0.25 µs µs 0 250 0 100 0 100 300 100 ns ns ns ns µs ns 50 ns 1000 300 4.0 0 300 300 0.6 0 50 0.25 0 50 Notes 1 2 2 Notes : All SCL specifications as well as start and stop conditions apply to both read and write operations. 1 The speed-related specifications are guaranteed characteristic points along a continuous curve of operation from DC to 1 MHz. 2 This parameter is periodically sampled and not 100% tested. Capacitance (TA = 25° C, f=1.0 MHz, VDD = 3V) Symbol Parameter CI/O Input/Output Capacitance (SDA) CIN Input Capacitance Max 8 6 Units pF pF Notes 1 1 Notes 1 This parameter is periodically sampled and not 100% tested. Power Cycle Timing (TA = -40° C to +85° C) Symbol Parameter tVR VDD Rise Time tVF VDD Fall Time tPU Power Up (VDD min) to First Access (Start condition) tPD Last Access (Stop condition) to Power Down (VDD min) Notes 1. 2. Min 50 100 5 0 Max - Units µs/V µs/V ms µs Notes 1, 2 1, 2 Slope measured at any point on VDD waveform. This parameter is characterized and not 100% tested. Rev. 1.0 May 2009 Page 9 of 12 FM24CL32 AC Test Conditions Input Pulse Levels Input rise and fall times Input and output timing levels Equivalent AC Load Circuit 0.1 VDD to 0.9 VDD 10 ns 0.5 VDD 3.6V 1100 Ω Diagram Notes All start and stop timing parameters apply to both read and write cycles. Clock specifications are identical for read and write cycles. Write timing parameters apply to slave address, word address, and write data bits. Functional relationships are illustrated in the relevant datasheet sections. These diagrams illustrate the timing parameters only. Output 100 pF Read Bus Timing tR ` tF t HIGH t SP t LOW t SP SCL t SU:SDA 1/fSCL t BUF t HD:DAT t SU:DAT SDA Start t DH t AA Stop Start Acknowledge Write Bus Timing t HD:DAT SCL t SU:DAT t HD:STA t SU:STO t AA SDA Start Data Retention (VDD = 2.7V to 3.6V) Symbol Parameter TDR Data Retention @ +75°C @ +80°C @ +85°C Rev. 1.0 May 2009 Stop Start Acknowledge Min Units 45 20 10 Years Years Years Notes Page 10 of 12 FM24CL32 Mechanical Drawing 8-pin SOIC (JEDEC Standard MS-012 variation AA) Refer to JEDEC MS-012 for complete dimensions and notes. All dimensions in millimeters. SOIC Package Marking Scheme XXXXXXX-P LLLLLLL RICYYWW Legend: XXXX= part number, P= package type LLLLLLL= lot code RIC=Ramtron Int’l Corp, YY=year, WW=work week Example: FM24CL32, “Green” SOIC package, Year 2009, Work Week 14 FM24CL32-G A90003G RIC0914 Rev. 1.0 May 2009 Page 11 of 12 FM24CL32 Revision History Revision 0.1 0.2 1.0 Rev. 1.0 May 2009 Date 11/25/2008 1/30/2009 5/11/2009 Summary Initial release – Product Preview. Added Power Cycle Timing specs and diagram. Changed to Preliminary status. Page 12 of 12