FM24CL16 16Kb FRAM Serial 3V Memory Features 16K bit Ferroelectric Nonvolatile RAM • Organized as 2,048 x 8 bits • Unlimited Read/Write Cycles • 10 year Data Retention • NoDelay™ Writes • Advanced High-Reliability Ferroelectric Process Fast Two-wire Serial Interface • Up to 1MHz maximum bus frequency • Direct hardware replacement for EEPROM Description The FM24CL16 is a 16-kilobit nonvolatile memory employing an advanced ferroelectric process. A ferroelectric random access memory or FRAM is nonvolatile and performs reads and writes like a RAM. It provides reliable data retention for over 10 years while eliminating the complexities, overhead, and system level reliability problems caused by EEPROM and other nonvolatile memories. Unlike serial EEPROMs, the FM24CL16 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 unlimited write endurance, orders of magnitude more endurance than EEPROM. Also, FRAM 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 FM24CL16 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 a long write time can cause data loss. The combination of features allows the system to write data more frequently, with less system overhead. Low Power Operation • New 2.7 - 3.6V operation • 75 µA Active Current (100 kHz) @ 3V • 1 µA Standby Current Industry Standard Configuration • Industrial Temperature -40° C to +85° C • 8-pin SOIC • New “Green” 8-pin SOIC Package Pin Configuration NC 1 8 VDD NC 2 7 WP NC 3 6 SCL VSS 4 5 SDA Pin Names SDA SCL WP VDD VSS Function Serial Data/Address Serial Clock Write Protect Supply Voltage Ground Ordering Information FM24CL16-S FM24CL16-G 8-pin SOIC 8-pin SOIC - “Green” Assembly Flow The FM24CL16 is available in an industry standard 8-pin SOIC and uses a two-wire protocol. The specifications are guaranteed over the industrial temperature range from -40°C to +85°C. Although the FM24CL16 is functionally compatible with the 5V FM24C16, it offers 3V operation and up to 1MHz bus speed. This product conforms to specifications per the terms of the Ramtron standard warranty. Production processing does not necessarily include testing of all parameters. Rev. 2.2 July 2003 Ramtron International Corporation 1850 Ramtron Drive, Colorado Springs, CO 80921 (800) 545-FRAM, (719) 481-7000, Fax (719) 481-7058 www.ramtron.com Page 1 of 13 FM24CL16 Address Latch Counter 256 x 64 FRAM Array 8 SDA ` Serial to Parallel Converter Data Latch SCL Control Logic WP Figure 1. Block Diagram Pin Description Pin Name SDA Type I/O SCL Input WP Input VDD VSS NC Rev 2.2 July 2003 Supply Supply - Pin Description Serial Data Address: This is a bi-directional data pin for the two-wire interface. It employs an open-drain output 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 input for the two-wire interface. Data is clocked-out on the falling edge and clocked-in on the rising edge. Write Protect: When WP is high, the entire array is write-protected. When WP is low, all addresses may be written. This pin is internally pulled down. Supply Voltage (3V) Ground No connect Page 2 of 13 FM24CL16 Overview Two-wire Interface The FM24CL16 is a serial FRAM memory. The memory array is logically organized as a 2,048 x 8 memory array and is accessed using an industry standard two-wire interface. Functional operation of the FRAM is similar to serial EEPROMs. The major difference between the FM24CL16 and a serial EEPROM with the same pinout relates to its superior write performance. The FM24CL16 employs a bi-directional two-wire bus protocol using few pins and little board space. Figure 2 illustrates a typical system configuration using the FM24CL16 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 FM24CL16, the user addresses 2,048 locations each with 8 data bits. These data bits are shifted serially. The 2,048 addresses are accessed using the two-wire protocol, which includes a slave address (to distinguish from other non-memory devices), a row address, and a segment address. The row address consists of 8-bits that specify one of 256 rows. The 3-bit segment address specifies one of 8 segments within each row. The complete 11-bit address specifies each byte uniquely. Most functions of the FM24CL16 either are controlled by the two-wire interface or handled automatically by on-board circuitry. 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 is complete. This is explained in more detail in the interface section below. 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 FM24CL16 is always 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, and Acknowledge. Figure 3 illustrates the signal conditions that define the four states. Detailed timing diagrams are in the electrical specifications. VDD Rmin = 1.1 KΩ Rmax = tR/Cbus Microcontroller SDA Note that the FM24CL16 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 data sheet tolerances to prevent incorrect operation. Rev 2.2 July 2003 SCL FM24CL16 SDA SCL Other Slave Device Figure 2. Typical System Configuration Page 3 of 13 FM24CL16 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 FM24CL16 must end with a Stop condition. If an operation is pending 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 read and write transactions begin with 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 prepare the FM24CL16 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. For system design considerations, keeping SCL in a low state while idle improves robustness. 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. Rev 2.2 July 2003 The receiver would fail to acknowledge for two distinct reasons. First is that a byte transfer fails. In this case, the No-Acknowledge ends 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. Second and most common, the receiver does not acknowledge to deliberately end an operation. For example, during a read operation, the FM24CL16 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 FM24CL16 to attempt to drive the bus on the next clock while the master is sending a new command such as a Stop. Slave Address The first byte that the FM24CL16 expects after a Start condition is the slave address. As shown in Figure 4, the slave address contains the device type, the page of memory to be accessed, 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 FM24CL16. The device type allows other types of functions to reside on the 2-wire bus within an identical address range. Bits 3-1 are the page select. They specify the 256-byte block of memory that is targeted for the current operation. Bit 0 is the read/write bit. A 0 indicates a write operation. Page 4 of 13 FM24CL16 Page Select Slave ID 1 0 1 0 A2 A1 Memory Operation A0 R/W Figure 4. Slave Address Word Address After the FM24CL16 (as receiver) acknowledges the slave ID, the master will place the word address on the bus for a write operation. The word address is the lower 8-bits of the address to be combined with the 3bits of the page select to specify the exact byte to be written. The complete 11-bit address is latched internally. No word address occurs for a read operation, though the 3-bit page select is latched internally. Reads always use the lower 8-bits that are held internally in the address latch. That is, reads always begin at the address following the previous access. A random read address can be loaded by doing a write operation as explained below. After transmission of each data byte, just prior to the acknowledge, the FM24CL16 increments the internal address latch. This allows the next sequential byte to be accessed with no additional addressing. After the last address (7FFh) is reached, the address latch will roll over to 000h. There is no limit on the number of bytes that can be accessed with a single read or write operation. Data Transfer After all address information has been transmitted, data transfer between the bus master and the FM24CL16 can begin. For a read operation the device will place 8 data bits on the bus then wait for an acknowledge. If the acknowledge occurs, the next sequential byte will be transferred. If the acknowledge is not sent, the read operation is concluded. For a write operation, the FM24CL16 will accept 8 data bits from the master then send an acknowledge. All data transfer occurs MSB (most significant bit) first. The FM24CL16 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 FRAM technology. These improvements result in some differences between the FM24CL16 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 slave ID then a word address as previously mentioned. The bus master indicates a write operation by setting the LSB of the Slave 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 7FFh to 000h. Unlike other nonvolatile memory technologies, there is no write delay with FRAM. 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. An actual memory array 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 FM24CL16 needs 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 FM24CL16 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. Figure 5 and 6 below illustrates both a single-byte and multiple-byte writes. Rev 2.2 July 2003 Page 5 of 13 FM24CL16 By Master Start S Address & Data Slave Address 0 A Word Address Stop A Data Byte A P By FM24CL16 Acknowledge Figure 5. Single Byte Write By Master Start S Address & Data Slave Address 0 A Word Address Stop A Data Byte By FM24CL16 A Data Byte A P Acknowledge Figure 6. Multiple Byte Write Read Operation There are two types of read operations. They are current address read and selective address read. In a current address read, the FM24CL16 uses the internal address latch to supply the lower 8 address bits. In a selective read, the user performs a procedure to set these lower address bits to a specific value. Current Address & Sequential Read As mentioned above the FM24CL16 uses an internal latch to supply the lower 8 address bits for a read operation. A current address read uses the existing value in the address latch as a starting place for the read operation. This is the address immediately following that of the last operation. To perform a current address read, the bus master supplies a slave address with the LSB set to 1. This indicates that a read operation is requested. The 3 page select bits in the slave ID specify the block of memory that is used for the read operation. On the next clock, the FM24CL16 will begin shifting out data from the current address. The current address is the 3 bits from the slave ID combined with the 8 bits that were 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 FM24CL16 should read out the next sequential byte. Rev 2.2 July 2003 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 FM24CL16 attempts to read out additional data onto the bus. The four valid methods are as follows. 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 the preferred method. 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. Bus contention may result. The bus master issues a start in the 9th clock cycle. Bus contention may result. If the internal address reaches 7FFh it will wrap around to 000h on the next read cycle. Figures 7 and 8 show the proper operation for current address reads. Selective (Random) Read A simple technique allows a user to select a random address location as the starting point for a read operation. It uses the first two bytes of a write operation to set the internal address byte followed by subsequent read operations. To perform a selective read, the bus master sends out the slave address with the LSB set to 0. This specifies a write operation. According to the write protocol, the bus master then sends the word address byte that is loaded into the internal address latch. After the FM24CL16 acknowledges the word address, the bus master issues a start condition. This simultaneously aborts the write operation and allows the read Page 6 of 13 FM24CL16 command to be issued with the slave address set to 1. The operation is now a current address read. This Start By Master operation is illustrated in Figure 9. No Acknowledge Address Stop S Slave Address By FM24CL16 1 A Data Byte Acknowledge 1 P Data Figure 7. Current Address Read Start By Master Address No Acknowledge Acknowledge Stop S Slave Address By FM24CL16 1 A Data Byte A Acknowledge Data Byte 1 P Data Figure 8. Sequential Read By Master Address Start Start Address No Acknowledge Acknowledge Stop S By FM24CL16 Slave Address 0 A Word Address A S Slave Address 1 A Acknowledge Data Byte A Data Byte 1 P Data Figure 9. Selective (Random) Read Endurance A typical EEPROM has a write endurance specification that is fixed. Surpassing the specified level of cycles on an EEPROM usually leads to a hard memory failure. The 24CL16 has no such limitation. Applications The versatility of FRAM technology fits into many diverse applications. Clearly the strength of higher write endurance and faster writes make FRAM superior to EEPROM in all but one-time programmable applications. The advantage is most obvious in data collection environments where writes are frequent and data must be nonvolatile. Rev 2.2 July 2003 The attributes of fast writes and high write endurance combine in many innovative ways. A short list of ideas is provided here. 1. Data collection. In applications where data is collected and saved, FRAM provides a superior alternative to other solutions. It is more cost effective than battery backup for SRAM and provides better write attributes than EEPROM. 2. Configuration. Any nonvolatile memory can retain a configuration. However, if the configuration changes and power failure is a possibility, the higher write endurance of FRAM allows changes to be recorded without restriction. Any time the system state is altered, the change can be written. This avoids writing to memory on power down when the available time is short and power scarce. Page 7 of 13 FM24CL16 3. High noise environments. Writing to EEPROM in a noisy environment can be challenging. When severe noise or power fluctuations are present, the long write time of EEPROM creates a window of vulnerability during which the write can be corrupted. The fast write of FRAM is complete within a microsecond. This time is typically too short for noise or power fluctuation to disturb it. 4. Time to market. In a complex system, multiple software routines may need to access the nonvolatile memory. In this environment the time delay associated with programming EEPROM adds undue complexity to the software development. Each software routine must wait for complete programming before allowing access to the next routine. When time to market is critical, FRAM can eliminate this simple obstacle. As soon as a write is issued to the FM24CL16, it is effectively done -- no waiting. powered by an RF field, the long programming time and high current consumption needed to write EEPROM is unattractive. FRAM provides a superior solution. The FM24CL16 is suitable for multi-chip RF/ID products. 6. Maintenance tracking. In sophisticated systems, the operating history and system state during a failure is important knowledge. Maintenance can be expedited when this information has been recorded. Due to the high write endurance, FRAM makes an ideal system log. In addition, the convenient 2-wire interface of the FM24CL16 allows memory to be distributed throughout the system using minimal additional resources. 5. RF/ID. In the area of contactless memory, FRAM provides an ideal solution. Since RF/ID memory is Rev 2.2 July 2003 Page 8 of 13 FM24CL16 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 +5.0V -1.0V to +5.0V and VIN < VDD+1.0V -55°C to + 125°C 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 =2.7V to 3.65V unless otherwise specified) Symbol Parameter Min Typ Max Units VDD Main Power Supply 2.7 3.65 V IDD VDD Supply Current 75 @ SCL = 100 kHz µA 150 @ SCL = 400 kHz µA 300 @ SCL = 1 MHz µA ISB Standby Current 1 µA ILI Input Leakage Current 10 µA ILO Output Leakage Current 10 µA VIH Input High Voltage 0.7 VDD VDD + 0.5 V VIL Input Low Voltage -0.3 0.3 VDD V VOL Output Low Voltage 0.4 V @ IOL = 3.0 mA RIN Address Input Resistance (WP, A2-A0) For VIN = VIL (max) 50 KΩ For VIN = VIH (min) 1 MΩ VHYS Input Hysteresis 0.05 VDD V Notes 1 2 3 3 4 4 5 4 Notes 1. SCL toggling between VDD-0.3V and VSS, other inputs VSS or VDD-0.3V. 2. SCL = SDA = VDD. All inputs VSS or VDD. Stop command issued. 3. VIN or VOUT = VSS to VDD. Does not apply to pins with pull down resistors. 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 much weaker (1MΩ) when the input voltage is above VIH. Rev 2.2 July 2003 Page 9 of 13 FM24CL16 AC Parameters (TA = -40° C to + 85° C, VDD =2.7V to 3.65V 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 Time Data In Setup Time 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 4.0 4.7 1.3 0.6 0.6 0.5 0.25 0.25 µs 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 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 Max CI/O Input/output capacitance (SDA) 8 CIN Input capacitance 6 Units pF pF Notes 1 1 Notes 1 This parameter is periodically sampled and not 100% tested. AC Test Conditions Input Pulse Levels Input rise and fall times Input and output timing levels 0.1 VDD to 0.9 VDD 10 ns 0.5 VDD Equivalent AC Load Circuit 3.65V 1100 Ω Output 100 pF Rev 2.2 July 2003 Page 10 of 13 FM24CL16 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 data sheet sections. These diagrams illustrate the timing parameters only. Read Bus Timing tR tF tHIGH tSP tLOW tSP SCL tSU:SDA 1/fSCL tBUF tHD:DAT tSU:D AT SDA Start tDH tAA Stop Start Acknowledge Write Bus Timing tHD:DAT SCL tHD:STA tSU:STO tSU:DAT tAA SDA Start Stop Start Data Retention (VDD = 2.7V to 3.65V unless otherwise specified) Parameter Min Units Data Retention 10 Years Rev 2.2 July 2003 Acknowledge Notes Page 11 of 13 FM24CL16 8-pin SOIC (JEDEC MS-012 variation AA) Index Area E H Pin 1 h D 45 ° A B e α L .10 mm .004 in. A1 C Selected Dimensions Refer to JEDEC MS-012 for complete dimensions and notes. Controlling dimensions in millimeters. Conversions to inches are not exact. Symbol A A1 B C D E e H h L α Rev 2.2 July 2003 Dim mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. Min 1.35 0.053 0.10 0.004 0.33 0.013 0.19 0.007 4.80 0.189 3.80 0.150 Nom. Max 1.75 0.069 0.25 0.010 0.51 0.020 0.25 0.010 5.00 0.197 4.00 0.157 1.27 BSC 0.050 BSC 5.80 0.228 0.25 0.010 0.40 0.016 0° 6.20 0.244 0.50 0.197 1.27 0.050 8° Page 12 of 13 FM24CL16 Revision History Revision 1.0 1.1 2.0 Date 2/15/01 9/29/01 2/22/02 2.1 2.2 3/24/02 7/11/03 Rev 2.2 July 2003 Summary Initial Release Endurance changed to unlimited. Changed to Production status. Added clarification to package standard and changed package name to SOIC. Added “green” package option. Changed storage temp range -55 to +125 C. Removed Data Retention note. Page 13 of 13