Features • Low-voltage and Standard-voltage Operation – 1.8 (VCC = 1.8V to 3.6V) Internally Organized as 32,768 x 8 Two-wire Serial Interface Schmitt Trigger, Filtered Inputs for Noise Suppression Bidirectional Data Transfer Protocol 1 MHz (3.6V, 2.7V, 2.5V), and 400 kHz (1.8V) Compatibility Write Protect Pin for Hardware and Software Data Protection 64-byte Page Write Mode (Partial Page Writes Allowed) Self-timed Write Cycle (5 ms Max) High Reliability – Endurance: One Million Write Cycles – Data Retention: 40 Years • Extended Temperature and Lead-free/Halogen-free Devices Available • 8-lead JEDEC PDIP, 8-lead JEDEC SOIC, 8-lead MAP, 8-lead TSSOP, and 8-ball dBGA2TM Packages • • • • • • • • • Two-wire Serial EEPROM 256K (32,768 x 8) Description The AT24C256B provides 262,144 bits of serial electrically erasable and programmable read-only memory (EEPROM) organized as 32,768 words of 8 bits each. The device’s cascadable feature allows up to eight devices to share a common two-wire bus. The device is optimized for use in many industrial and commercial applications where low-power and low-voltage operation are essential. The devices are available in space-saving 8-lead JEDEC PDIP, 8-lead JEDEC SOIC, 8-lead MAP, 8-lead TSSOP, and 8-ball dBGA2 packages. In addition, the entire family is available in a 1.8V (1.8V to 3.6V) version. Table 1. Pin Configurations Pin Name Function A0–A2 Address Inputs SDA Serial Data SCL Serial Clock Input WP Write Protect NC No Connect GND Ground 8-lead PDIP AT24C256B Preliminary 8-lead SOIC A0 1 8 VCC A0 1 8 VCC A1 2 7 WP A1 2 7 WP A2 3 6 SCL A2 3 6 SCL GND 4 5 SDA GND 4 5 SDA 8-lead dBGA2 8-lead TSSOP VCC 8 1 A0 WP 7 2 A1 SCL 6 3 A2 SDA 5 4 GND A0 1 8 VCC A1 2 7 WP A2 3 6 SCL GND 4 5 SDA Bottom View 8-lead MAP VCC 8 1 A0 WP 7 2 A1 SCL 6 3 A2 SDA 5 4 GND Bottom View Rev. 5080A–SEEPR–9/04 1 Absolute Maximum Ratings* Operating Temperature......................................−55°C to +125°C Storage Temperature .........................................−65°C to +150°C Voltage on Any Pin with Respect to Ground ........................................ −1.0V to +5.0V Maximum Operating Voltage ............................................ 4.3V *NOTICE: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. DC Output Current........................................................ 5.0 mA Figure 1. Block Diagram 2 AT24C256B 5080A–SEEPR–9/04 AT24C256B Pin Description SERIAL CLOCK (SCL): The SCL input is used to positive-edge clock data into each EEPROM device and negative-edge clock data out of each device. SERIAL DATA (SDA): The SDA pin is bidirectional for serial data transfer. This pin is opendrain driven and may be wire-ORed with any number of other open-drain or open-collector devices. DEVICE/PAGE ADDRESSES (A2, A1, A0): The A2, A1, and A0 pins are device address inputs that are hardwired (directly to GND or to Vcc) for compatibility with other AT24Cxx devices. When the pins are hardwired, as many as eight 256K devices may be addressed on a single bus system. (Device addressing is discussed in detail under “Device Addressing,” page 8.) A device is selected when a corresponding hardware and software match is true. If these pins are left floating, the A2, A1, and A0 pins will be internally pulled down to GND. However, due to capacitive coupling that may appear during customer applications, Atmel recommends always connecting the address pins to a known state. When using a pull-up resistor, Atmel recommends using 10kΩ or less. WRITE PROTECT (WP): The write protect input, when connected to GND, allows normal write operations. When WP is connected directly to Vcc, all write operations to the memory are inhibited. If the pin is left floating, the WP pin will be internally pulled down to GND. However, due to capacitive coupling that may appear during customer applications, Atmel recommends always connecting the WP pins to a known state. When using a pull-up resistor, Atmel recommends using 10kΩ or less. Memory Organization AT24C256B, 256K SERIAL EEPROM: The 256K is internally organized as 512 pages of 64 bytes each. Random word addressing requires a 15-bit data word address. 3 5080A–SEEPR–9/04 Table 1. Pin Capacitance (1) Applicable over recommended operating range from TA = 25°C, f = 1.0 MHz, VCC = +1.8V Symbol Test Condition CI/O CIN Note: Max Units Conditions Input/Output Capacitance (SDA) 8 pF VI/O = 0V Input Capacitance (A 0, A1, SCL) 6 pF VIN = 0V 1. This parameter is characterized and is not 100% tested. Table 2. DC Characteristics Applicable over recommended operating range from: TAI = −40°C to +85°C, VCC = +1.8V to +3.6V (unless otherwise noted) Symbol Parameter Test Condition Min Typ Max Units VCC1 Supply Voltage 3.6 V ICC1 Supply Current VCC = 3.6V READ at 400 kHz 1.0 2.0 mA ICC2 Supply Current VCC = 3.6V WRITE at 400 kHz 2.0 3.0 mA ISB1 Standby Current (1.8V option) VCC = 1.8V 1.0 µA ILI Input Leakage Current VIN = VCC or VSS 0.10 3.0 µA ILO Output Leakage Current VOUT = VCC or VSS 0.05 3.0 µA VIL Input Low Level(1) −0.6 VCC x 0.3 V VCC x 0.7 VCC + 0.5 V 1.8 VCC = 3.6V VIN = VCC or VSS (1) 3.0 VIH Input High Level VOL2 Output Low Level VCC = 3.0V IOL = 2.1 mA 0.4 V VOL1 Output Low Level VCC = 1.8V IOL = 0.15 mA 0.2 V Notes: 4 1. VIL min and VIH max are reference only and are not tested. AT24C256B 5080A–SEEPR–9/04 AT24C256B Table 3. AC Characteristics (Industrial Temperature) Applicable over recommended operating range from TAI = −40°C to +85°C, VCC = +1.8V to +3.6V, CL = 100 pF (unless otherwise noted). Test conditions are listed in Note 2. 1.8-volt Min 2.5-volt Symbol Parameter fSCL Clock Frequency, SCL tLOW Clock Pulse Width Low 1.3 0.4 0.4 µs tHIGH Clock Pulse Width High 0.6 0.4 0.4 µs tAA Clock Low to Data Out Valid 0.05 tBUF Time the bus must be free before a new transmission can start(1) 1.3 0.5 0.5 µs tHD.STA Start Hold Time 0.6 0.25 0.25 µs tSU.STA Start Set-up Time 0.6 0.25 0.25 µs tHD.DAT Data In Hold Time 0 0 0 µs tSU.DAT Data In Set-up Time 100 100 100 ns Inputs Rise Time tR Max Min 400 (1) (1) 0.9 Max 3.6-volt Min 1000 0.05 0.55 0.05 Max Units 1000 kHz 0.55 µs 0.3 0.3 0.3 µs 300 100 100 ns tF Inputs Fall Time tSU.STO Stop Set-up Time 0.6 0.25 0.25 µs tDH Data Out Hold Time 50 50 50 ns tWR Write Cycle Time Endurance(1) 25°C, Page Mode, 3.3V Notes: 5 5 1,000,000 5 ms Write Cycles 1. This parameter is characterized and is not 100% tested. 2. AC measurement conditions: RL (connects to VCC): 1.3 kΩ (2.5V, 3.6V), 10 kΩ (1.8V) Input pulse voltages: 0.3 VCC to 0.7 VCC Input rise and fall times: ≤ 50 ns Input and output timing reference voltages: 0.5 VCC 5 5080A–SEEPR–9/04 Device Operation CLOCK and DATA TRANSITIONS: The SDA pin is normally pulled high with an external device. Data on the SDA pin may change only during SCL low time periods (see Figure 2). Data changes during SCL high periods will indicate a start or stop condition as defined below. Figure 2. Data Validity START CONDITION: A high-to-low transition of SDA with SCL high is a start condition that must precede any other command (see Figure 3). Figure 3. Start and Stop Definition SDA SCL START STOP STOP CONDITION: A low-to-high transition of SDA with SCL high is a stop condition. After a read sequence, the stop command will place the EEPROM in a standby power mode (see Figure 3). ACKNOWLEDGE: All addresses and data words are serially transmitted to and from the EEPROM in 8-bit words. The EEPROM sends a “0” during the ninth clock cycle to acknowledge that it has received each word. STANDBY MODE: The AT24C256B features a low-power standby mode that is enabled upon power-up and after the receipt of the stop bit and the completion of any internal operations. 6 AT24C256B 5080A–SEEPR–9/04 AT24C256B MEMORY RESET: After an interruption in protocol, power loss or system reset, any two-wire part can be reset by following these steps: 1. Clock up to 9 cycles; 2. Look for SDA high in each cycle while SCL is high; 3. Create a start condition as SDA is high. Figure 4. Bus Timing Figure 5. Write Cycle Timing SCL SDA 8th BIT ACK WORDn (1) twr STOP CONDITION Note: START CONDITION 1. The write cycle time tWR is the time from a valid stop condition of a write sequence to the end of the internal clear/write cycle. 7 5080A–SEEPR–9/04 Figure 6. Output Acknowledge Device Addressing The 256K EEPROM requires an 8-bit device address word following a start condition to enable the chip for a read or write operation (see Figure 7). The device address word consists of a mandatory “1”, “0” sequence for the first four most significant bits as shown. This is common to all two-wire EEPROM devices. Figure 7. Device Address 1 MSB 0 1 0 A2 A1 A0 R/W LSB The next three bits are the A2, A1, A0 device address bits to allow as many as eight devices on the same bus. These bits must compare to their corresponding hardwired input pins. The A2, A1, and A0 pins use an internal proprietary circuit that biases them to a logic low condition if the pins are allowed to float. The eighth bit of the device address is the read/write operation select bit. A read operation is initiated if this bit is high, and a write operation is initiated if this bit is low. Upon a compare of the device address, the EEPROM will output a “0”. If a compare is not made, the device will return to a standby state. DATA SECURITY: The AT24C256B has a hardware data protection scheme that allows the user to write protect the whole memory when the WP pin is at VCC. 8 AT24C256B 5080A–SEEPR–9/04 AT24C256B Write Operations BYTE WRITE: A write operation requires two 8-bit data word addresses following the device address word and acknowledgment. Upon receipt of this address, the EEPROM will again respond with a “0” and then clock in the first 8-bit data word. Following receipt of the 8-bit data word, the EEPROM will output a “0”. The addressing device, such as a microcontroller, must then terminate the write sequence with a stop condition. At this time the EEPROM enters an internally-timed write cycle, tWR, to the nonvolatile memory. All inputs are disabled during this write cycle and the EEPROM will not respond until the write is complete (see Figure 8). Figure 8. Byte Write Note: * = DON’T CARE bit PAGE WRITE: The 256K EEPROM is capable of 64-byte page writes. A page write is initiated the same way as a byte write, but the microcontroller does not send a stop condition after the first data word is clocked in. Instead, after the EEPROM acknowledges receipt of the first data word, the microcontroller can transmit up to 63 more data words. The EEPROM will respond with a “0” after each data word received. The microcontroller must terminate the page write sequence with a stop condition (see Figure 9). Figure 9. Page Write Note: * = DON’T CARE bit The data word address lower six bits are internally incremented following the receipt of each data word. The higher data word address bits are not incremented, retaining the memory page row location. When the word address, internally generated, reaches the page boundary, the following byte is placed at the beginning of the same page. If more than 64 data words are transmitted to the EEPROM, the data word address will “roll over” and previous data will be overwritten. The address “roll over” during write is from the last byte of the current page to the first byte of the same page. ACKNOWLEDGE POLLING: Once the internally-timed write cycle has started and the EEPROM inputs are disabled, acknowledge polling can be initiated. This involves sending a start condition followed by the device address word. The read/write bit is representative of the operation desired. Only if the internal write cycle has completed will the EEPROM respond with a “0”, allowing the read or write sequence to continue. 9 5080A–SEEPR–9/04 Read Operations Read operations are initiated the same way as write operations with the exception that the read/write select bit in the device address word is set to “1”. There are three read operations: current address read, random address read, and sequential read. CURRENT ADDRESS READ: The internal data word address counter maintains the last address accessed during the last read or write operation, incremented by one. This address stays valid between operations as long as the chip power is maintained. The address “roll over” during read is from the last byte of the last memory page, to the first byte of the first page. Once the device address with the read/write select bit set to “1” is clocked in and acknowledged by the EEPROM, the current address data word is serially clocked out. The microcontroller does not respond with an input “0” but does generate a following stop condition (see Figure 10). Figure 10. Current Address Read RANDOM READ: A random read requires a “dummy” byte write sequence to load in the data word address. Once the device address word and data word address are clocked in and acknowledged by the EEPROM, the microcontroller must generate another start condition. The microcontroller now initiates a current address read by sending a device address with the read/write select bit high. The EEPROM acknowledges the device address and serially clocks out the data word. The microcontroller does not respond with a “0” but does generate a following stop condition (see Figure 11). Figure 11. Random Read Note: 10 * = DON’T CARE bit AT24C256B 5080A–SEEPR–9/04 AT24C256B SEQUENTIAL READ: Sequential reads are initiated by either a current address read or a random address read. After the microcontroller receives a data word, it responds with an acknowledge. As long as the EEPROM receives an acknowledge, it will continue to increment the data word address and serially clock out sequential data words. When the memory address limit is reached, the data word address will “roll over” and the sequential read will continue. The sequential read operation is terminated when the microcontroller does not respond with a “0” but does generate a following stop condition (see Figure 12). Figure 12. Sequential Read 11 5080A–SEEPR–9/04 AT24C256B Ordering Information Ordering Code Package Operation Range 8P3 8S1 8U2-1 8A2 8Y1 Lead-free/Halogen-free Industrial Temperature (−40°C to 85°C AT24C256B-10PU-1.8 AT24C256BN-10SU-1.8 AT24C256BU2-10UU-1.8 AT24C256B-10TU-1.8 AT24C256BY1-10YU-1.8 Package Type 8P3 8-lead, 0.300" Wide, Plastic Dual Inline Package (PDIP) 8S1 8-lead, 0.150" Wide, Plastic Gull Wing Small Outline Package (JEDEC SOIC) 8U2-1 8-ball, die Ball Grid Array Package (dBGA2) 8A2 8-lead, 0.170" Wide, Thin Shrink Small Outline Package (TSSOP) 8Y1 8-lead, 4.90 mm x 3.00 mm Body, Dual Footprint, Non-leaded, Miniature Array Package (MAP) Options −1.8 12 Low-voltage (1.8V to 3.6V) AT24C256B 5080A–SEEPR–9/04 AT24C256B Packaging Information 8P3 – PDIP E 1 E1 N Top View c eA End View COMMON DIMENSIONS (Unit of Measure = inches) D e D1 A2 A SYMBOL A b2 b3 b 4 PLCS Side View L NOM MAX NOTE – – 0.210 2 A2 0.115 0.130 0.195 b 0.014 0.018 0.022 5 b2 0.045 0.060 0.070 6 b3 0.030 0.039 0.045 6 c 0.008 0.010 0.014 D 0.355 0.365 0.400 3 D1 0.005 – – 3 E 0.300 0.310 0.325 4 E1 0.240 0.250 0.280 3 e 0.100 BSC eA L Notes: MIN 0.300 BSC 0.115 0.130 4 0.150 2 1. This drawing is for general information only; refer to JEDEC Drawing MS-001, Variation BA, for additional information. 2. Dimensions A and L are measured with the package seated in JEDEC seating plane Gauge GS-3. 3. D, D1 and E1 dimensions do not include mold Flash or protrusions. Mold Flash or protrusions shall not exceed 0.010 inch. 4. E and eA measured with the leads constrained to be perpendicular to datum. 5. Pointed or rounded lead tips are preferred to ease insertion. 6. b2 and b3 maximum dimensions do not include Dambar protrusions. Dambar protrusions shall not exceed 0.010 (0.25 mm). 01/09/02 R 2325 Orchard Parkway San Jose, CA 95131 TITLE 8P3, 8-lead, 0.300" Wide Body, Plastic Dual In-line Package (PDIP) DRAWING NO. REV. 8P3 B 13 5080A–SEEPR–9/04 8S1 – JEDEC SOIC C 1 E E1 L N ∅ Top View End View e B COMMON DIMENSIONS (Unit of Measure = mm) A SYMBOL A1 D Side View MIN NOM MAX A 1.35 – 1.75 A1 0.10 – 0.25 b 0.31 – 0.51 C 0.17 – 0.25 D 4.80 – 5.00 E1 3.81 – 3.99 E 5.79 – 6.20 e NOTE 1.27 BSC L 0.40 – 1.27 ∅ 0˚ – 8˚ Note: These drawings are for general information only. Refer to JEDEC Drawing MS-012, Variation AA for proper dimensions, tolerances, datums, etc. 10/7/03 R 14 1150 E. Cheyenne Mtn. Blvd. Colorado Springs, CO 80906 TITLE 8S1, 8-lead (0.150" Wide Body), Plastic Gull Wing Small Outline (JEDEC SOIC) DRAWING NO. 8S1 REV. B AT24C256B 5080A–SEEPR–9/04 AT24C256B 8U2-1 – dBGA2 D A1 BALL PAD CORNER 1. b E A1 A2 Top View A A1 BALL PAD CORNER Side View 1 2 A B e C D (e1) d (d1) COMMON DIMENSIONS (Unit of Measure = mm) Bottom View SYMBOL MIN 8 Solder Balls A 0.81 0.91 1.00 A1 0.15 0.20 0.25 A2 0.40 0.45 0.50 b 0.25 0.30 0.35 MAX NOM D 2.35 BSC 1. Dimension 'b' is measured at the maximum solder ball diameter. E 3.73 BSC This drawing is for general information only. e 0.75 BSC e1 0.74 REF d 0.75 BSC d1 0.80 REF NOTE 1 6/24/03 R 1150 E. Cheyenne Mtn. Blvd. Colorado Springs, CO 80906 TITLE 8U2-1, 8-ball, 2.35 x 3.73 mm Body, 0.75 mm pitch, Small Die Ball Grid Array Package (dBGA2) DRAWING NO. PO8U2-1 REV. A 15 5080A–SEEPR–9/04 8A2 – TSSOP 3 2 1 Pin 1 indicator this corner E1 E L1 N L Top View End View COMMON DIMENSIONS (Unit of Measure = mm) SYMBOL A b D MIN NOM MAX NOTE 2.90 3.00 3.10 2, 5 3, 5 E e D A2 6.40 BSC E1 4.30 4.40 4.50 A – – 1.20 A2 0.80 1.00 1.05 b 0.19 – 0.30 e Side View L 0.65 BSC 0.45 L1 Notes: 0.60 0.75 1.00 REF 1. This drawing is for general information only. Refer to JEDEC Drawing MO-153, Variation AA, for proper dimensions, tolerances, datums, etc. 2. Dimension D does not include mold Flash, protrusions or gate burrs. Mold Flash, protrusions and gate burrs shall not exceed 0.15 mm (0.006 in) per side. 3. Dimension E1 does not include inter-lead Flash or protrusions. Inter-lead Flash and protrusions shall not exceed 0.25 mm (0.010 in) per side. 4. Dimension b does not include Dambar protrusion. Allowable Dambar protrusion shall be 0.08 mm total in excess of the b dimension at maximum material condition. Dambar cannot be located on the lower radius of the foot. Minimum space between protrusion and adjacent lead is 0.07 mm. 5. Dimension D and E1 to be determined at Datum Plane H. 5/30/02 R 16 4 2325 Orchard Parkway San Jose, CA 95131 TITLE 8A2, 8-lead, 4.4 mm Body, Plastic Thin Shrink Small Outline Package (TSSOP) DRAWING NO. 8A2 REV. B AT24C256B 5080A–SEEPR–9/04 AT24C256B 8Y1 – MAP PIN 1 INDEX AREA A 1 3 2 4 PIN 1 INDEX AREA E1 D1 D L 8 Bottom View COMMON DIMENSIONS (Unit of Measure = mm) A MIN NOM MAX A – – 0.90 A1 0.00 – 0.05 D 4.70 4.90 5.10 E 2.80 3.00 3.20 D1 0.85 1.00 1.15 E1 0.85 1.00 1.15 b 0.25 0.30 0.35 SYMBOL Side View 5 e End View Top View 6 b A1 E 7 e L NOTE 0.65 TYP 0.50 0.60 0.70 2/28/03 R 2325 Orchard Parkway San Jose, CA 95131 TITLE 8Y1, 8-lead (4.90 x 3.00 mm Body) MSOP Array Package (MAP) Y1 DRAWING NO. REV. 8Y1 C 17 5080A–SEEPR–9/04 Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 487-2600 Regional Headquarters Europe Atmel Sarl Route des Arsenaux 41 Case Postale 80 CH-1705 Fribourg Switzerland Tel: (41) 26-426-5555 Fax: (41) 26-426-5500 Asia Room 1219 Chinachem Golden Plaza 77 Mody Road Tsimshatsui East Kowloon Hong Kong Tel: (852) 2721-9778 Fax: (852) 2722-1369 Japan 9F, Tonetsu Shinkawa Bldg. 1-24-8 Shinkawa Chuo-ku, Tokyo 104-0033 Japan Tel: (81) 3-3523-3551 Fax: (81) 3-3523-7581 Atmel Operations Memory 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 436-4314 RF/Automotive Theresienstrasse 2 Postfach 3535 74025 Heilbronn, Germany Tel: (49) 71-31-67-0 Fax: (49) 71-31-67-2340 Microcontrollers 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 436-4314 La Chantrerie BP 70602 44306 Nantes Cedex 3, France Tel: (33) 2-40-18-18-18 Fax: (33) 2-40-18-19-60 ASIC/ASSP/Smart Cards 1150 East Cheyenne Mtn. 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The Company assumes no responsibility for any errors which may appear in this document, reserves the right to change devices or specifications detailed herein at any time without notice, and does not make any commitment to update the information contained herein. No licenses to patents or other intellectual property of Atmel are granted by the Company in connection with the sale of Atmel products, expressly or by implication. Atmel’s products are not authorized for use as critical components in life support devices or systems. © Atmel Corporation 2004. All rights reserved. Atmel®, logo and combinations thereof are registered trademarks, and Everywhere You Are SM and dBGA2 ™ are trademarks of Atmel Corporation or its subsidiaries. Other terms and product names may be the trademarks of others. Printed on recycled paper. 5080A–SEEPR–9/04