AT24C256C Datasheet by Microchip Technology

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6‘ MICRDCHIP
AT24C256C
I²C-Compatible (2-Wire)
Serial EEPROM 256Kbit (32,768 x 8)
Features
Low-Voltage and Standard-Voltage Operation:
– VCC = 1.7V to 5.5V
Internally Organized as 32,768 x 8 (256K)
Industrial Temperature Range: -40°C to +85°C
• I2C-Compatible (2-Wire) Serial Interface:
100 kHz Standard mode, 1.7V to 5.5V
400 kHz Fast mode, 1.7V to 5.5V
1 MHz Fast Mode Plus (FM+), 2.5V to 5.5V
Schmitt Trigger, Filtered Inputs for Noise Suppression
Bidirectional Data Transfer Protocol
• WriteProtect Pin for Full Array Hardware Data Protection
Ultra Low Active Current (3 mA maximum) and Standby Current (6 μA maximum)
64-Byte Page Write Mode:
Partial page writes allowed
Random and Sequential Read Modes
• SelfTimed Write Cycle within 5 ms Maximum
ESD Protection > 4,000V
High Reliability:
Endurance: 1,000,000 write cycles
Data retention: 100 years
Green Package Options (Lead-free/Halide-free/RoHS compliant)
Die Sale Options: Wafer Form and Bumped Wafers
Packages
8-Lead SOIC, 8-Lead TSSOP, 8-Pad UDFN and 8-Ball VFBGA
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 1
Table of Contents
Features.......................................................................................................................... 1
Packages.........................................................................................................................1
1. Package Types (not to scale).................................................................................... 4
2. Pin Descriptions.........................................................................................................5
2.1. Device Address Inputs (A0, A1, A2).............................................................................................5
2.2. Ground......................................................................................................................................... 5
2.3. Serial Data (SDA).........................................................................................................................5
2.4. Serial Clock (SCL)........................................................................................................................5
2.5. Write-Protect (WP)....................................................................................................................... 6
2.6. Device Power Supply................................................................................................................... 6
3. Description.................................................................................................................7
3.1. System Configuration Using 2-Wire Serial EEPROMs ................................................................7
3.2. Block Diagram.............................................................................................................................. 8
4. Electrical Characteristics........................................................................................... 9
4.1. Absolute Maximum Ratings..........................................................................................................9
4.2. DC and AC Operating Range.......................................................................................................9
4.3. DC Characteristics....................................................................................................................... 9
4.4. AC Characteristics......................................................................................................................10
4.5. Electrical Specifications..............................................................................................................11
5. Device Operation and Communication....................................................................13
5.1. Clock and Data Transition Requirements...................................................................................13
5.2. Start and Stop Conditions.......................................................................................................... 13
5.3. Acknowledge and No-Acknowledge...........................................................................................14
5.4. Standby Mode............................................................................................................................ 14
5.5. Software Reset...........................................................................................................................15
6. Memory Organization.............................................................................................. 16
6.1. Device Addressing..................................................................................................................... 16
7. Write Operations......................................................................................................18
7.1. Byte Write...................................................................................................................................18
7.2. Page Write..................................................................................................................................18
7.3. Acknowledge Polling.................................................................................................................. 19
7.4. Write Cycle Timing..................................................................................................................... 19
7.5. Write Protection..........................................................................................................................20
8. Read Operations..................................................................................................... 21
8.1. Current Address Read................................................................................................................21
8.2. Random Read............................................................................................................................ 21
AT24C256C
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 2
8.3. Sequential Read.........................................................................................................................22
9. Device Default Condition from Microchip................................................................ 23
10. Packaging Information.............................................................................................24
10.1. Package Marking Information.....................................................................................................24
11. Revision History.......................................................................................................34
The Microchip Web Site................................................................................................ 35
Customer Change Notification Service..........................................................................35
Customer Support......................................................................................................... 35
Product Identification System........................................................................................36
Microchip Devices Code Protection Feature................................................................. 36
Legal Notice...................................................................................................................37
Trademarks................................................................................................................... 37
Quality Management System Certified by DNV.............................................................38
Worldwide Sales and Service........................................................................................39
AT24C256C
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 3
1. Package Types (not to scale)
8-Lead SOIC/TSSOP
(Top View)
A0 1
2
3
4
8
7
6
5
A1
A2
GND
VCC
WP
SCL
SDA
1
2
3
4
8
7
6
5
A0
A1
A2
GND
VCC
WP
SCL
SDA
8-Ball VFBGA
(Top View)
A0
A1
A2
GND
VCC
WP
SCL
SDA
8-Pad UDFN
(Top View)
1
2
3
4
8
7
6
5
AT24C256C
Package Types (not to scale)
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 4
0(2) (2) (2) (2)
2. Pin Descriptions
The descriptions of the pins are listed in Table 2-1.
Table 2-1. Pin Function Table
Name 8Lead SOIC 8Lead TSSOP 8Pad UDFN(1)8Ball VFBGA Function
A0(2)1 1 1 1 Device Address Input
A1(2)2 2 2 2 Device Address Input
A2(2)3 3 3 3 Device Address Input
GND 4 4 4 4 Ground
SDA 5 5 5 5 Serial Data
SCL 6 6 6 6 Serial Clock
WP(2)7 7 7 7 Write-Protect
VCC 8 8 8 8 Device Power Supply
Note: 
1. The exposed pad on this package can be connected to GND or left floating.
2. If the A0, A1, A2 or WP pins are not driven, they are internally pulled down to GND. In order to
operate in a wide variety of application environments, the pulldown mechanism is intentionally
designed to be somewhat strong. Once these pins are biased above the CMOS input buffer’s trip
point (~0.5 x VCC), the pulldown mechanism disengages. Microchip recommends connecting these
pins to a known state whenever possible.
2.1 Device Address Inputs (A0, A1, A2)
The A0, A1 and A2 pins are device address inputs that are hard-wired (directly to GND or to VCC) for
compatibility with other 2-wire Serial EEPROM devices. When the pins are hard-wired, as many as eight
devices may be addressed on a single bus system. A device is selected when a corresponding hardware
and software match is true. If these pins are left floating, the A0, A1 and A2 pins will be internally pulled
down to GND. However, due to capacitive coupling that may appear in customer applications, Microchip
recommends always connecting the address pins to a known state. When using a pullup resistor,
Microchip recommends using 10 kΩ or less.
2.2 Ground
The ground reference for the power supply. GND should be connected to the system ground.
2.3 Serial Data (SDA)
The SDA pin is an opendrain bidirectional input/output pin used to serially transfer data to and from the
device. The SDA pin must be pulled high using an external pullup resistor (not to exceed 10 kΩ in value)
and may be wire-ORed with any number of other opendrain or opencollector pins from other devices on
the same bus.
2.4 Serial Clock (SCL)
The SCL pin is used to provide a clock to the device and to control the flow of data to and from the
device. Command and input data present on the SDA pin is always latched in on the rising edge of SCL,
AT24C256C
Pin Descriptions
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 5
while output data on the SDA pin is clocked out on the falling edge of SCL. The SCL pin must either be
forced high when the serial bus is idle or pulled high using an external pullup resistor.
2.5 Write-Protect (WP)
The write-protect input, when connected to GND, allows normal write operations. When the WP pin is
connected directly to VCC, all write operations to the protected 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 in customer applications, Microchip recommends always connecting the WP
pin to a known state. When using a pullup resistor, Microchip recommends using 10 kΩ or less.
Table 2-2. Write-Protect
WP Pin Status Part of the Array Protected
At VCC Full Array
At GND Normal Write Operations
2.6 Device Power Supply
The VCC pin is used to supply the source voltage to the device. Operations at invalid VCC voltages may
produce spurious results and should not be attempted.
AT24C256C
Pin Descriptions
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 6
1mm Vcc Vommxy T LLLJ. 1. T LLLJ. 1.
3. Description
The AT24C256C 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 cascading feature allows up
to eight devices to share a common 2wire bus. The device is optimized for use in many industrial and
commercial applications where lowpower and lowvoltage operation are essential. The devices are
available in spacesaving 8lead SOIC, 8lead TSSOP, 8pad UDFN and 8ball VFBGA packages. All
packages operate from 1.7V to 5.5V.
3.1 System Configuration Using 2-Wire Serial EEPROMs
I2C Bus Master:
Microcontroller
Slave 0
AT24CXXX
VCC
WP
SDA
SCL
A0
A1
A2
GND
VCC
GND
SCL
SDA
WP
RPUP(max) = tR(max)
0.8473 x CL
RPUP(min) = VCC - VOL(max)
IOL
Slave 1
AT24CXXX
VCC
WP
SDA
SCL
A0
A1
A2
GND
Slave 7
AT24CXXX
VCC
WP
SDA
SCL
A0
A1
A2
GND
VCC
AT24C256C
Description
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 7
3.2 Block Diagram
1 page
Start
Stop
Detector
GND
A2
Memory
System Control
Module
High Voltage
Generation Circuit
Data & ACK
Input/Output Control
Address Register
and Counter
Write
Protection
Control
DOUT
DIN
Hardware
Address
Comparator
VCC
WP
SCL
SDA
Power
On Reset
Generator
EEPROM Array
Column Decoder
Row Decoder
Data Register
A1
A0
AT24C256C
Description
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 8
4. Electrical Characteristics
4.1 Absolute Maximum Ratings
Temperature under bias -55°C to +125°C
Storage temperature -65°C to +150°C
VCC 6.25V
Voltage on any pin with respect to ground -1.0V to +7.0V
DC output current 5.0 mA
ESD protection >4 kV
Note:  Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to
the device. This is a stress rating only and functional operation of the device at these or any other
conditions above those indicated in the operation listings of this specification are not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
4.2 DC and AC Operating Range
Table 4-1. DC and AC Operating Range
AT24C256C
Operating Temperature (Case) Industrial Temperature Range -40°C to +85°C
VCC Power Supply Low Voltage Grade 1.7V to 5.5V
4.3 DC Characteristics
Table 4-2. DC Characteristics
Parameter Symbol Minimum Typical(1)Maximum Units Test Conditions
Supply Voltage VCC1 1.7 5.5 V
Supply Current ICC1 1.0 2.0 mA VCC = 5.0V, Read at 400 kHz
Supply Current ICC2 2.0 3.0 mA VCC = 5.0V, Write at 400 kHz
Standby Current ISB1 1.0 μA VCC = 1.7V, VIN = VCC or GND
6.0 μA VCC = 5.0V, VIN = VCC or GND
Input Leakage
Current
ILI 0.10 3.0 μA VIN = VCC or GND; VCC = 5.0V
Output Leakage
Current
ILO 0.05 3.0 μA VOUT = VCC or GND;
VCC = 5.0V
Input Low Level VIL -0.6 — VCC x 0.3 V Note 2
Input High Level VIH VCC x 0.7 VCC + 0.5 V Note 2
AT24C256C
Electrical Characteristics
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 9
Parameter Symbol Minimum Typical(1)Maximum Units Test Conditions
Output Low Level VOL1 0.2 V VCC = 1.7V, IOL = 0.15 mA
Output Low Level VOL2 0.4 V VCC = 3.0V, IOL = 2.1 mA
Note: 
1. Typical values characterized at TA = +25°C unless otherwise noted.
2. This parameter is characterized but is not 100% tested in production.
4.4 AC Characteristics
Table 4-3. AC Characteristics(1)
Parameter Symbol 1.7V 2.5V, 5.0V Units
Min. Max. Min. Max.
Clock Frequency, SCL fSCL 400 1000 kHz
Clock Pulse Width Low tLOW 1300 — 500 ns
Clock Pulse Width High tHIGH 600 — 400 — ns
Noise Suppression Time(2)tI— 100 — 50 ns
Clock Low to Data Out Valid tAA 50 900 50 450 ns
Bus Free Time between Stop and
Start(2)
tBUF 1300 — 500 ns
Start Hold Time tHD.STA 600 — 250 — ns
Start Setup Time tSU.STA 600 — 250 — ns
Data In Hold Time tHD.DAT 0 — 0 — ns
Data In Setup Time tSU.DAT 100 — 100 — ns
Inputs Rise Time(2)tR— 300 — 300 ns
Inputs Fall Time(2)tF— 300 — 100 ns
Stop Set-up Time tSU.STO 600 — 250 — ns
Data Out Hold Time tDH 50 — 50 — ns
Write Cycle Time tWR — 5 — 5 ms
Note: 
1. AC measurement conditions:
– CL: 100 pF
– RPUP (SDA bus line pull-up resistor to VCC): 1.3 kΩ (1000 kHz), 4 kΩ (400 kHz), 10 kΩ
(100 kHz)
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 x VCC
AT24C256C
Electrical Characteristics
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 10
2. This parameter is ensured by characterization and is not 100% tested.
Figure 4-1. Bus Timing
SCL
SDA In
SDA Out
tF
tHIGH
tLOW
tR
tDH
tAA tBUF
tSU.STO
tSU.DAT
tHD.DAT
tHD.STA
tSU.STA
4.5 Electrical Specifications
4.5.1 Power-up Requirements and Reset Behavior
During a power-up sequence, the VCC supplied to the AT24C256C should monotonically rise from GND to
the minimum VCC level, as specified in Table 4-1, with a slew rate no faster than 0.1 V/μs.
4.5.1.1 Device Reset
To prevent inadvertent write operations or any other spurious events from occurring during a powerup
sequence, the AT24C256C includes a Power-on Reset (POR) circuit. Upon powerup, the device will not
respond to any commands until the VCC level crosses the internal voltage threshold (VPOR) that brings the
device out of Reset and into Standby mode.
The system designer must ensure the instructions are not sent to the device until the VCC supply has
reached a stable value greater than or equal to the minimum VCC level. Additionally, once the VCC is
greater than or equal to the minimum VCC level, the bus master must wait at least tPUP before sending the
first command to the device. See Table 4-4 for the values associated with these powerup parameters.
Table 4-4. Power-up Conditions(1)
Symbol Parameter Min. Max. Units
tPUP Time required after VCC is stable before the device can accept commands 100 µs
VPOR Power-on Reset Threshold Voltage 1.5 V
tPOFF Minimum time at VCC = 0V between power cycles 500 ms
Note: 
1. These parameters are characterized but they are not 100% tested in production.
If an event occurs in the system where the VCC level supplied to the AT24C256C drops below the
maximum VPOR level specified, it is recommended that a full power cycle sequence be performed by first
driving the VCC pin to GND, waiting at least the minimum tPOFF time and then performing a new power-up
sequence in compliance with the requirements defined in this section.
AT24C256C
Electrical Characteristics
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 11
4.5.2 Pin Capacitance
Table 4-5. Pin Capacitance(1)
Symbol Test Condition Max. Units Conditions
CI/O Input/Output Capacitance (SDA) 8 pF VI/O = 0V
CIN Input Capacitance (A0, A1, A2 and SCL) 6 pF VIN = 0V
Note: 
1. This parameter is characterized but is not 100% tested in production.
4.5.3 EEPROM Cell Performance Characteristics
Table 4-6. EEPROM Cell Performance Characteristics
Operation Test Condition Min. Max. Units
Write Endurance(1)TA = 25°C, VCC = 3.3V,
Page Write mode
1,000,000 Write Cycles
Data Retention(1)TA = 55°C 100 Years
Note: 
1. Performance is determined through characterization and the qualification process.
AT24C256C
Electrical Characteristics
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 12
5. Device Operation and Communication
The AT24C256C operates as a slave device and utilizes a simple I2C-compatible 2-wire digital serial
interface to communicate with a host controller, commonly referred to as the bus master. The master
initiates and controls all read and write operations to the slave devices on the serial bus, and both the
master and the slave devices can transmit and receive data on the bus.
The serial interface is comprised of just two signal lines: Serial Clock (SCL) and Serial Data (SDA).
The SCL pin is used to receive the clock signal from the master, while the bidirectional SDA pin is used to
receive command and data information from the master as well as to send data back to the master. Data
is always latched into the AT24C256C on the rising edge of SCL and always output from the device on
the falling edge of SCL. Both the SCL and SDA pin incorporate integrated spike suppression filters and
Schmitt Triggers to minimize the effects of input spikes and bus noise.
All command and data information is transferred with the Most Significant bit (MSb) first. During bus
communication, one data bit is transmitted every clock cycle, and after eight bits (one byte) of data have
been transferred, the receiving device must respond with either an Acknowledge (ACK) or a
No-Acknowledge (NACK) response bit during a ninth clock cycle (ACK/NACK clock cycle) generated by
the master. Therefore, nine clock cycles are required for every one byte of data transferred. There are no
unused clock cycles during any read or write operation, so there must not be any interruptions or breaks
in the data stream during each data byte transfer and ACK or NACK clock cycle.
During data transfers, data on the SDA pin must only change while SCL is low, and the data must remain
stable while SCL is high. If data on the SDA pin changes while SCL is high, then either a Start or a Stop
condition will occur. Start and Stop conditions are used to initiate and end all serial bus communication
between the master and the slave devices. The number of data bytes transferred between a Start and a
Stop condition is not limited and is determined by the master. In order for the serial bus to be idle, both
the SCL and SDA pins must be in the logic-high state at the same time.
5.1 Clock and Data Transition Requirements
The SDA pin is an open-drain terminal and therefore must be pulled high with an external pullup resistor.
SCL is an input pin that can either be driven high or pulled high using an external pullup resistor. Data on
the SDA pin may change only during SCL low time periods. Data changes during SCL high periods will
indicate a Start or Stop condition as defined below. The relationship of the AC timing parameters with
respect to SCL and SDA for the AT24C256C are shown in the timing waveform in Figure 4-1. The AC
timing characteristics and specifications are outlined in 4.4 AC Characteristics.
5.2 Start and Stop Conditions
5.2.1 Start Condition
A Start condition occurs when there is a high-to-low transition on the SDA pin while the SCL pin is at a
stable logic ‘1’ state and will bring the device out of Standby mode. The master uses a Start condition to
initiate any data transfer sequence; therefore, every command must begin with a Start condition. The
device will continuously monitor the SDA and SCL pins for a Start condition but will not respond unless
one is detected. Refer to Figure 5-1 for more details.
5.2.2 Stop Condition
A Stop condition occurs when there is a low-to-high transition on the SDA pin while the SCL pin is stable
in the logic ‘1’ state.
AT24C256C
Device Operation and Communication
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 13
H “H Q H Hm Q Common
The master can use the Stop condition to end a data transfer sequence with the AT24C256C, which will
subsequently return to Standby mode. The master can also utilize a repeated Start condition instead of a
Stop condition to end the current data transfer if the master will perform another operation. Refer to
Figure 5-1 for more details.
5.3 Acknowledge and No-Acknowledge
After every byte of data is received, the receiving device must confirm to the transmitting device that it
has successfully received the data byte by responding with what is known as an Acknowledge (ACK).
An ACK is accomplished by the transmitting device first releasing the SDA line at the falling edge of the
eighth clock cycle followed by the receiving device responding with a logic ‘0’ during the entire high period
of the ninth clock cycle.
When the AT24C256C is transmitting data to the master, the master can indicate that it is done receiving
data and wants to end the operation by sending a logic ‘1’ response to the AT24C256C instead of an
ACK response during the ninth clock cycle. This is known as a No-Acknowledge (NACK) and is
accomplished by the master sending a logic ‘1’ during the ninth clock cycle, at which point the
AT24C256C will release the SDA line so the master can then generate a Stop condition.
The transmitting device, which can be the bus master or the Serial EEPROM, must release the SDA line
at the falling edge of the eighth clock cycle to allow the receiving device to drive the SDA line to a logic ‘0
to ACK the previous 8bit word. The receiving device must release the SDA line at the end of the ninth
clock cycle to allow the transmitter to continue sending new data. A timing diagram has been provided in
Figure 5-1 to better illustrate these requirements.
Figure 5-1. Start Condition, Data Transitions, Stop Condition and Acknowledge
SCL
SDA
SDA
Must Be
Stable
SDA
Change
Allowed
SDA
Change
Allowed
Acknowledge
Valid
Stop
Condition
Start
Condition
1 2 8 9
SDA
Must Be
Stable Acknowledge Window
The transmitting device (Master or Slave)
must release the SDA line at this point to allow
the receiving device (Master or Slave) to drive the
SDA line low to ACK the previous 8-bit word.
The receiver (Master or Slave)
must release the SDA line at
this point to allow the transmitter
to continue sending new data.
5.4 Standby Mode
The AT24C256C features a lowpower Standby mode that is enabled when any one of the following
occurs:
A valid power-up sequence is performed (see 4.5.1 Power-up Requirements and Reset Behavior).
A Stop condition is received by the device unless it initiates an internal write cycle (see 7. Write
Operations).
At the completion of an internal write cycle (see 7. Write Operations).
AT24C256C
Device Operation and Communication
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 14
5.5 Software Reset
After an interruption in protocol, power loss or system Reset, any 2wire device can be protocol reset by
clocking SCL until SDA is released by the EEPROM and goes high. The number of clock cycles until SDA
is released by the EEPROM will vary. The software Reset sequence should not take more than nine
dummy clock cycles. Once the software Reset sequence is complete, new protocol can be sent to the
device by sending a Start condition followed by the protocol. Refer to Figure 5-2 for an illustration.
Figure 5-2. Software Reset
SCL 9
Device is
8321
SDA
Dummy Clock Cycles
SDA Released
Software Reset
by EEPROM
In the event that the device is still non-responsive or remains active on the SDA bus, a power cycle must
be used to reset the device (see 4.5.1 Power-up Requirements and Reset Behavior).
AT24C256C
Device Operation and Communication
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 15
6. Memory Organization
The AT24C256C is internally organized as 512 pages of 64 bytes each.
6.1 Device Addressing
Accessing the device requires an 8bit device address byte following a Start condition to enable the
device for a read or write operation. Since multiple slave devices can reside on the serial bus, each slave
device must have its own unique address so the master can access each device independently.
The Most Significant four bits of the device address byte is referred to as the device type identifier. The
device type identifier ‘1010' (Ah) is required in bits 7 through 4 of the device address byte (see Table 6-1).
Following the 4-bit device type identifier are the hardware slave address bits, A0, A1 and A2. These bits
can be used to expand the address space by allowing up to eight Serial EEPROM devices on the same
bus. These hardware slave address bits must correlate with the voltage level on the corresponding
hardwired device address input pins A0, A1 and A2. The A0, A1 and A2 pins use an internal proprietary
circuit that automatically biases the pin to a logic ‘0’ state if the pin is allowed to float. In order to operate
in a wide variety of application environments, the pulldown mechanism is intentionally designed to be
somewhat strong. Once the pin is biased above the CMOS input buffer's trip point (~0.5 x VCC), the
pulldown mechanism disengages. Microchip recommends connecting the A0, A1 and A2 pins to a known
state whenever possible.
The eighth bit (bit 0) of the device address byte is the Read/Write Select bit. A read operation is initiated if
this bit is high and a write operation is initiated if this bit is low.
Upon the successful comparison of the device address byte, the AT24C256C will return an ACK. If a valid
comparison is not made, the device will NACK.
Table 6-1. Device Addressing
Package Device Type Identifier Hardware Slave Address Bits R/W Select
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
SOIC, TSSOP, UDFN,
VFBGA
1 0 1 0 A2 A1 A0 R/W
For all operations except the current address read, two 8bit word address bytes must be transmitted to
the device immediately following the device address byte. The word address bytes consist of the 15bit
memory array word address, and are used to specify which byte location in the EEPROM to start reading
or writing.
The first word address byte contains the seven Most Significant bits of the word address (A14 through
A8) in bit positions six through zero, as seen in Table 6-2. Bit 7 of the first word address byte is a “don't
care” bit as it is outside of the addressable 256Kbit range. Upon completion of the first word address
byte, the AT24C256C will return an ACK.
Table 6-2. First Word Address Byte
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
XA14 A13 A12 A11 A10 A9 A8
AT24C256C
Memory Organization
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 16
Next, the second word address byte is sent to the device which provides the remaining eight bits of the
word address (A7 through A0). Upon completion of the second word address byte, the AT24C256C will
return an ACK. See Table 6-3 to review these bit positions.
Table 6-3. Second Word Address Byte
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
A7 A6 A5 A4 A3 A2 A1 A0
AT24C256C
Memory Organization
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 17
7. Write Operations
All write operations for the AT24C256C begin with the master sending a Start condition, followed by a
device address byte with the R/W bit set to logic ‘0’, and then by the word address bytes. The data
value(s) to be written to the device immediately follow the word address bytes.
7.1 Byte Write
The AT24C256C supports the writing of a single 8bit byte. Selecting a data word in the AT24C256C
requires a 15bit word address.
Upon receipt of the proper device address and the word address bytes, the EEPROM will send an
Acknowledge. The device will then be ready to receive the 8bit data word. Following receipt of the 8bit
data word, the EEPROM will respond with an ACK. The addressing device, such as a bus master, must
then terminate the write operation with a Stop condition. At that time, the EEPROM will enter an internally
selftimed write cycle, which will be completed within tWR, while the data word is being programmed into
the nonvolatile EEPROM. All inputs are disabled during this write cycle, and the EEPROM will not
respond until the write is complete.
Figure 7-1. Byte Write
SCL
SDA
Start Condition
by Master
Device Address Byte First Word Address Byte
MSB MSB
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
1 0 1 0 A2 A1 A0 0 0
Second Word Address Byte Data Word
Stop Condition
by Master
MSB MSB
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
D7 D6 D5 D4 D3 D2 D1 D0 0
X A14 A13 A12 A11 A10 A9 A8 0
ACK
from Slave
ACK
from Slave
ACK
from Slave
ACK
from Slave
A7 A6 A5 A4 A3 A2 A1 A0 0
7.2 Page Write
A page write operation allows up to 64 bytes to be written in the same write cycle, provided all bytes are
in the same row of the memory array (where address bits A14 through A6 are the same). Partial page
writes of less than 64 bytes are also allowed.
A page write is initiated the same way as a byte write, but the bus master 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 bus master can transmit up to sixty three additional data words. The EEPROM will respond with
an ACK after each data word is received. Once all data to be written has been sent to the device, the bus
master must issue a Stop condition (see Figure 7-2) at which time the internally self-timed write cycle will
begin.
The lower six bits of the word address are internally incremented following the receipt of each data word.
The higher order address bits are not incremented and retain the memory page row location. Page write
AT24C256C
Write Operations
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 18
Send any Write pm|ocol 4» Send S|op condmnn to Inmate me wn|e cyme
operations are limited to writing bytes within a single physical page, regardless of the number of bytes
actually being written. When the incremented word address reaches the page boundary, the address
counter will rollover to the beginning of the same page. Nevertheless, creating a rollover event should
be avoided as previously loaded data in the page could become unintentionally altered.
Figure 7-2. Page Write
SCL
SDA
Start Condition
by Master ACK
from Slave
ACK
from Slave
Device Address Byte First Word Address Byte
MSB MSB
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
1 0 1 0 A2 A1 A0 0 0 X A14 A13 A12 A11 A10 A9 A8 0
ACK
from Slave
ACK
from Slave
Stop Condition
by Master
ACK
from Slave
Second Word Address Byte Data Word (n) Data Word (n+x), max of 64 without rollover
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
A7 A6 A5 A4 A3 A2 A1 A0 0 D7 D6 D5 D4 D3 D2 D1 D0 0 D7 D6 D5 D4 D3 D2 D1 D0 0
MSB MSB MSB
7.3 Acknowledge Polling
An Acknowledge Polling routine can be implemented to optimize timesensitive applications that would
prefer not to wait the fixed maximum write cycle time (tWR). This method allows the application to know
immediately when the Serial EEPROM write cycle has completed, so a subsequent operation can be
started.
Once the internally selftimed write cycle has started, an Acknowledge Polling routine can be initiated.
This involves repeatedly sending a Start condition followed by a valid device address byte with the R/W
bit set at logic ‘0’. The device will not respond with an ACK while the write cycle is ongoing. Once the
internal write cycle has completed, the EEPROM will respond with an ACK, allowing a new read or write
operation to be immediately initiated. A flowchart has been included below in Figure 7-3 to better illustrate
this technique.
Figure 7-3. Acknowledge Polling Flowchart
7.4 Write Cycle Timing
The length of the selftimed write cycle (tWR) is defined as the amount of time from the Stop condition that
begins the internal write cycle to the Start condition of the first device address byte, sent to the
AT24C256C
Write Operations
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 19
AT24C256C that it subsequently responds to with an ACK. Figure 7-4 has been included to show this
measurement. During the internally selftimed write cycle, any attempts to read from or write to the
memory array will not be processed.
Figure 7-4. Write Cycle Timing
tWR
Stop
Condition
Start
Condition
Data Word n
ACKD0
SDA
Stop
Condition
SCL 8 9
ACK
First Acknowledge from the device
to a valid device address sequence after
write cycle is initiated. The minimum tWR
can only be determined through
the use of an ACK Polling routine.
9
7.5 Write Protection
The AT24C256C utilizes a hardware data protection scheme that allows the user to writeprotect the
entire memory contents when the WP pin is at VCC (or a valid VIH). No write protection will be set if the
WP pin is at GND or left floating.
Table 7-1. AT24C256C Write-Protect Behavior
WP Pin Voltage Part of the Array Protected
VCC Full Array
GND None Write Protection Not Enabled
The status of the WP pin is sampled at the Stop condition for every byte write or page write operation
prior to the start of an internally selftimed write cycle. Changing the WP pin state after the Stop condition
has been sent will not alter or interrupt the execution of the write cycle.
If an attempt is made to write to the device while the WP pin has been asserted, the device will
acknowledge the device address, word address and data bytes, but no write cycle will occur when the
Stop condition is issued. The device will immediately be ready to accept a new read or write command.
AT24C256C
Write Operations
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 20
8. 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 byte must be a logic '1'. There are three read operations:
Current Address Read
Random Address Read
Sequential Read
8.1 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 the VCC is
maintained to the part. The address rollover during a read is from the last byte of the last page to the first
byte of the first page of the memory.
A current address read operation will output data according to the location of the internal data word
address counter. This is initiated with a Start condition, followed by a valid device address byte with the
R/W bit set to logic ‘1’. The device will ACK this sequence and the current address data word is serially
clocked out on the SDA line. All types of read operations will be terminated if the bus master does not
respond with an ACK (it NACKs) during the ninth clock cycle. After the NACK response, the master may
send a Stop condition to complete the protocol, or it can send a Start condition to begin the next
sequence.
Figure 8-1. Current Address Read
SCL
SDA
Device Address Byte Data Word (n)
Start Condition
by Master ACK
from Slave
NACK
from Master
Stop Condition
by Master
MSB MSB
1 0 1 0 A2A1A01 0 D7 D6 D5 D4 D3 D2 D1 D0 1
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
8.2 Random Read
A random read begins in the same way as a byte write operation does to load in a new data word
address. This is known as a “dummy write” sequence; however, the data byte and the Stop condition of
the byte write must be omitted to prevent the part from entering an internal write cycle. Once the device
address and word address are clocked in and acknowledged by the EEPROM, the bus master must
generate another Start condition. The bus master now initiates a current address read by sending a Start
condition, followed by a valid device address byte with the R/W bit set to logic ’1’. The EEPROM will ACK
the device address and serially clock out the data word on the SDA line. All types of read operations will
be terminated if the bus master does not respond with an ACK (it NACKs) during the ninth clock cycle.
After the NACK response, the master may send a Stop condition to complete the protocol, or it can send
a Start condition to begin the next sequence.
AT24C256C
Read Operations
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 21
Figure 8-2. Random Read
SCL
SDA
Start Condition
by Master
Device Address Byte First Word Address Byte
MSB MSB
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
1 0 1 0 A2 A1 A0 0 0
Dummy Write
Start Condition
by Master
Device Address Byte Data Word (n)
Stop Condition
by Master
MSB MSB
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
1 0 1 0 A2 A1 A0 1 0 D7 D6 D5 D4 D3 D2 D1 D0 1
X A14 A13 A12 A11 A10 A9 A8 0
ACK
from Slave
ACK
from Slave
ACK
from Slave
NACK
from Master
Second Word Address Byte
MSB
A7 A6 A5 A4 A3 A2 A1 A0 0
ACK
from Slave
8.3 Sequential Read
Sequential reads are initiated by either a current address read or a random read. After the bus master
receives a data word, it responds with an Acknowledge. As long as the EEPROM receives an ACK, it will
continue to increment the word address and serially clock out sequential data words. When the maximum
memory address is reached, the data word address will roll-over and the sequential read will continue
from the beginning of the memory array. All types of read operations will be terminated if the bus master
does not respond with an ACK (it NACKs) during the ninth clock cycle. After the NACK response, the
master may send a Stop condition to complete the protocol, or it can send a Start condition to begin the
next sequence.
Figure 8-3. Sequential Read
SCL
SDA
Start Condition
by Master ACK
from Slave
ACK
from Master
Device Address Byte Data Word (n)
MSB MSB
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
1 0 1 0 A2A1A01 0 D7 D6 D5 D4 D3 D2 D1 D0 0
ACK
from Master
NACK
from Master
Stop Condition
by Master
ACK
from Master
Data Word (n+1) Data Word (n+2) Data Word (n+x)
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
D7 D6 D5 D4 D3 D2 D1 D0 0 D7 D6 D5 D4 D3 D2 D1 D0 0 D7 D6 D5 D4 D3 D2 D1 D0 1
MSB MSB MSB
AT24C256C
Read Operations
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 22
9. Device Default Condition from Microchip
The AT24C256C is delivered with the EEPROM array set to logic ‘1’, resulting in FFh data in all locations.
AT24C256C
Device Default Condition from Microchip
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 23
Catalog Number Truncauan W = Veal Y = Vear WW = Work Week oIAssemmy “A: = Mlmmum Vonage 16 2016 20 2020 6 2016 D' 2020 02 Week 2 L 17me Lnl Number orTrace Code
10. Packaging Information
10.1 Package Marking Information
AT24C256C: Package Marking Information
Catalog Number Truncation
AT24C256C Truncation Code ###: 2EC
Date Codes Voltages
YY = Year Y = Year WW = Work Week of Assembly % = Minimum Voltage
16: 2016 20: 2020 6: 2016 0: 2020 02: Week 2 L: 1.7V min
17: 2017 21: 2021 7: 2017 1: 2021 04: Week 4
18: 2018 22: 2022 8: 2018 2: 2022 ...
19: 2019 23: 2023 9: 2019 3: 2023 52: Week 52
Country of Origin Device Grade Atmel Truncation
CO = Country of Origin H or U: Industrial Grade AT: Atmel
ATM: Atmel
ATML: Atmel
Lot Number or Trace Code
NNN = Alphanumeric Trace Code (2 Characters for Small Packages)
8-lead SOIC
YYWWNNN
###% CO
ATMLHYWW
8-lead TSSOP
YYWWNNN
###%CO
ATHYWW
8-pad UDFN
###
H%
NNN
2.0 x 3.0 mm Body
Note 2: Package drawings are not to scale
Note 1: designates pin 1
2.35 x 3.73 mm Body
8-ball VFBGA
###U
WWNNN
AT24C256C
Packaging Information
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 24
M ll]: N , I Ein‘L
0.25 C A–B D
C
SEATING
PLANE
TOP VIEW
SIDE VIEW
VIEW A–A
0.10 C
0.10 C
Microchip Technology Drawing No. C04-057-SN Rev D Sheet 1 of 2
8X
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
Note:
8-Lead Plastic Small Outline (SN) - Narrow, 3.90 mm (.150 In.) Body [SOIC]
© 2017 Microchip Technology Inc.
R
12
N
h
h
A1
A2
A
A
B
e
D
E
E
2
E1
2
E1
NOTE 5
NOTE 5
NX b
0.10 C A–B
2X
H 0.23
(L1)
L
R0.13
R0.13
VIEW C
SEE VIEW C
NOTE 1
D
AT24C256C
Packaging Information
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 25
Unws NHLLIMETERS D1menslon anls MIN | NOM | MAX Number a! PM: N a Man e 1 27 BSC averan He1ghl A - - 1 75 Mo1ded Package Th1ckness A2 1.25 - - Standoff A1 0.10 - o 25 Overal1W1dm E s 00 BSC Molded Package Wldlh E1 3 90 BSC OveraH Length D 4 90 BSC Chamfev (Opllonal) h 0.25 - o 50 Fool Length L 0.40 - 1 27 Fool Ang1e v2 0‘ - a“ Lead Tmckness c 0.17 - o 25 Lead w‘dm n 0.31 - o 51 Mmd Dvafl Ang1e Top 01 5: - 15: 5 5: - 15:
Microchip Technology Drawing No. C04-057-SN Rev D Sheet 2 of 2
8-Lead Plastic Small Outline (SN) - Narrow, 3.90 mm (.150 In.) Body [SOIC]
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
Note:
© 2017 Microchip Technology Inc.
R
Foot Angle 0° - 8°
15°-5°
Mold Draft Angle Bottom
15°-5°
Mold Draft Angle Top
0.51-0.31
b
Lead Width
0.25-0.17
c
Lead Thickness
1.27-0.40LFoot Length
0.50-0.25hChamfer (Optional)
4.90 BSCDOverall Length
3.90 BSCE1Molded Package Width
6.00 BSCEOverall Width
0.25-0.10
A1
Standoff
--1.25A2Molded Package Thickness
1.75--AOverall Height
1.27 BSC
e
Pitch
8NNumber of Pins
MAXNOMMINDimension Limits
MILLIMETERSUnits
protrusions shall not exceed 0.15mm per side.
3. Dimensions D and E1 do not include mold flash or protrusions. Mold flash or
REF: Reference Dimension, usually without tolerance, for information purposes only.
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
1. Pin 1 visual index feature may vary, but must be located within the hatched area.
2. § Significant Characteristic
4. Dimensioning and tolerancing per ASME Y14.5M
Notes:
§
Footprint L1 1.04 REF
5. Datums A & B to be determined at Datum H.
AT24C256C
Packaging Information
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 26
JUN D :1 [ fl L\L\
RECOMMENDED LAND PATTERN
Microchip Technology Drawing C04-2057-SN Rev B
8-Lead Plastic Small Outline (SN) - Narrow, 3.90 mm Body [SOIC]
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
Notes:
Dimensioning and tolerancing per ASME Y14.5M1.
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
Note:
© 2017 Microchip Technology Inc.
R
Dimension Limits
Units
CContact Pad Spacing
Contact Pitch
MILLIMETERS
1.27 BSC
MIN
E
MAX
5.40
Contact Pad Length (X8)
Contact Pad Width (X8)
Y1
X1
1.55
0.60
NOM
E
X1
C
Y1
SILK SCREEN
AT24C256C
Packaging Information
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 27
Number of Fms Pmch OveraH Hewgm Mmded Package Thickness Slandofl OveraH Wwdlh Mmded Package wmm Mmded Package Length Foot Leng|h Footplinl Pom Ang‘e Lead Thmkness c Lead Width b
©2007 Microchip Technology Inc. DS00049AR-page 117
M
Packaging Diagrams and Parameters
8-Lead Plastic Thin Shrink Small Outline (ST) – 4.4 mm Body [TSSOP]
Notes:
1. Pin 1 visual index feature may vary, but must be located within the hatched area.
2. Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.15 mm per side.
3. Dimensioning and tolerancing per ASME Y14.5M.
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
REF: Reference Dimension, usually without tolerance, for information purposes only.
Note: For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
Units MILLIMETERS
Dimension Limits MIN NOM MAX
Number of Pins N 8
Pitch e 0.65 BSC
Overall Height A 1.20
Molded Package Thickness A2 0.80 1.00 1.05
Standoff A1 0.05 0.15
Overall Width E 6.40 BSC
Molded Package Width E1 4.30 4.40 4.50
Molded Package Length D 2.90 3.00 3.10
Foot Length L 0.45 0.60 0.75
Footprint L1 1.00 REF
Foot Angle φ0° – 8°
Lead Thickness c 0.09 0.20
Lead Width b 0.19 0.30
D
N
E
E1
NOTE 1
1 2
b
e
c
A
A1
A2
L1 L
φ
Microchip Technology Drawing C04-086B
AT24C256C
Packaging Information
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 28
8-Lead Plastic Thin Shrink Small Oulline (ST) - 4.4 mm Body [TSSOP] .—CI—— HUDH’ 5 L».— H \ ,l w lk SlLK SCREEN RECOMMENDED LAND PA'I'I'ERN um; MILLIMETERS Dlmanslon lells MlN l NOM | MAX Contacl Pllch E o 65 Bsc Comacl Pad Spaclng c1 5 90 Comm F'ad Wldm (xa) Xl 0.45 Contact Pad Length (x5) w 1 A5 Dlslanoe Between Pads (3 o 20 Noles' 1 Dlmenslonlng and lolerancmg per ASME YM 5M BSC Baslc Dimenslon Thenrellcally exam value Shawn wllhoul tolerances. Mlcrocmp Technology Drawing No cm-zoaeA
DS00049BC-page 96 2009 Microchip Technology Inc.
M
Packaging Diagrams and Parameters
Note: For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
AT24C256C
Packaging Information
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 29
fl! I-llfik * {{wu WIT—fl \\\ f ‘ ‘ __&f *Hfl‘nfl 1 J NJL ADP e g "
© 2018 Microchip Technology Incorporated
B
A
0.10 C
0.10 C
(DATUM B)
(DATUM A)
C
SEATING
PLANE
12
N
2X
TOP VIEW
SIDE VIEW
NOTE 1
12
N
0.10 C A B
0.10 C A B
0.10 C
0.08 C
Microchip Technology Drawing C04-21355-Q4B Rev A Sheet 1 of 2
2X
8X
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
Note:
8-Lead Ultra Thin Plastic Dual Flat, No Lead Package (Q4B) - 2x3 mm Body [UDFN]
Atmel Legacy YNZ Package
D
E
D2
E2 K
L8X b
e
e
2
0.10 C A B
0.05 C
A
(A3)
A1
BOTTOM VIEW
AT24C256C
Packaging Information
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 30
© 2018 Microchip Technology Incorporated
REF: Reference Dimension, usually without tolerance, for information purposes only.
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
1.
2.
3.
Notes:
Pin 1 visual index feature may vary, but must be located within the hatched area.
Package is saw singulated
Dimensioning and tolerancing per ASME Y14.5M
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
Note:
Number of Terminals
Overall Height
Terminal Width
Overall Width
Terminal Length
Exposed Pad Width
Terminal Thickness
Pitch
Standoff
Units
Dimension Limits
A1
A
b
E2
A3
e
L
E
N
0.50 BSC
0.152 REF
1.20
0.35
0.18
0.50
0.00
0.25
0.40
1.30
0.55
0.02
3.00 BSC
MILLIMETERS
MIN NOM
8
1.40
0.45
0.30
0.60
0.05
MAX
K-0.20 -Terminal-to-Exposed-Pad
Overall Length
Exposed Pad Length
D
D2 1.40
2.00 BSC
1.50 1.60
Microchip Technology Drawing C04-21355-Q4B Rev A Sheet 2 of 2
8-Lead Ultra Thin Plastic Dual Flat, No Lead Package (Q4B) - 2x3 mm Body [UDFN]
Atmel Legacy YNZ Package
AT24C256C
Packaging Information
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 31
© 2018 Microchip Technology Incorporated
RECOMMENDED LAND PATTERN
Dimension Limits
Units
Optional Center Pad Width
Optional Center Pad Length
Contact Pitch
Y2
X2
1.40
1.60
MILLIMETERS
0.50 BSC
MIN
E
MAX
Contact Pad Length (X8)
Contact Pad Width (X8)
Y1
X1
0.85
0.30
NOM
12
8
CContact Pad Spacing 2.90
Contact Pad to Center Pad (X8) G1 0.20
Thermal Via Diameter V
Thermal Via Pitch EV
0.30
1.00
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
Notes:
Dimensioning and tolerancing per ASME Y14.5M
For best soldering results, thermal vias, if used, should be filled or tented to avoid solder loss during
reflow process
1.
2.
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
Note:
Microchip Technology Drawing C04-21355-Q4B Rev A
8-Lead Ultra Thin Plastic Dual Flat, No Lead Package (Q4B) - 2x3 mm Body [UDFN]
Atmel Legacy YNZ Package
X2
Y2
Y1
SILK SCREEN X1
E
C
EV
G2
G1
ØV
Contact Pad to Contact Pad (X6) G2 0.33
AT24C256C
Packaging Information
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 32
OOOAw‘fl O$$$wL I] nDIEm CA\B| nUOEm c J J
DRAWING NO. REV. TITLE GPC
8U2-1 G
6/11/13
8U2-1, 8-ball, 2.35 x 3.73 mm Body, 0.75 mm pitch,
Very Thin, Fine-Pitch Ball Grid Array Package
(VFBGA)
GWW
COMMON DIMENSIONS
(Unit of Measure = mm)
SYMBOL MIN NOM MAX NOTE
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
D 2.35 BSC
E 3.73 BSC
e 0.75 BSC
e1 0.74 REF
d 0.75 BSC
d1 0.80 REF
2. Dimension 'b' is measured at the maximum solder ball diameter.
1. This drawing is for general
3. Solder ball composition shall be 95.5Sn-4.0Ag-.5Cu.
Notes:
A
d0.08 C
C
f0.10 C
A1
A2
Øb
j n 0.15 mC A B
jn0.08 mC
A
(4X)
d0.10
B
A1 BALL
PAD
CORNER
D
E
SIDE VIEW
TOP VIEW
e
(e1)
d
2 1
D
C
B
A
A1 BALL PAD CORNER
(d1)
8 SOLDER BALLS
BOTTOM VIEW
Note:  For the most current package drawings, please see the Microchip Packaging Specification located
at http://www.microchip.com/packaging.
AT24C256C
Packaging Information
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 33
11. Revision History
Atmel Document 8568 Revision A (September 2009)
Initial document release.
Atmel Document 8568 Revision B (March 2010)
Part Markings and ordering detail/codes updated.
Atmel Document 8568 Revision C (May 2010)
Update 8S1 and 8A2 package drawings.
Atmel Document 8568 Revision D (September 2011)
Atmel global device marking alignment. Update 8S1, 8A2 to 8X, 8MA2, and 8U2-1 package drawings.
Atmel Document 8568 Revision E (August 2012)
Update template and Atmel logo. Correct 8-lead UDFN to 8-pad UDFN. Update AC characteristics from
μs to ns units and their respective values. Update part marking description.
Atmel Document 8568 Revision F (January 2015)
Add the UDFN Expanded Quantity Option. Update 8X, 8MA2, and 8U2-1 package outline drawings, the
ordering information section, and the disclaimer page.
Revision A (August 2018)
Updated to the Microchip template. Microchip DS20006042 replaces Atmel document 8568. Corrected
tLOW typo from 400 ns to 500 ns. Corrected tAA typo from 550 ns to 450 ns. Updated Part Marking
Information. Updated the “Software Reset” section. Added ESD rating. Removed lead finish designation.
Updated trace code format in package markings. Updated section content throughout for clarification.
Added a figure for “System Configuration Using 2-Wire Serial EEPROMs”. Added POR recommendations
section. Updated the SOIC, TSSOP and UDFN package drawings to Microchip format.
AT24C256C
Revision History
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 34
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Local sales offices are also available to help customers. A listing of sales offices and locations is included
in the back of this document.
Technical support is available through the web site at: http://www.microchip.com/support
AT24C256C
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 35
1E
Product Identification System
To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.
Product Family
24C = Standard I2C-compatible
Serial EEPROM
Device Density
Shipping Carrier Option
Device Grade or
Wafer/Die Thickness
Package Option
256 = 256 Kilobit
B = Bulk (Tubes)
T = Tape and Reel, Standard Quantity Option
E = Tape and Reel, Extended Quantity Option
Operating Voltage
L = 1.7V to 5.5V
H or U = Industrial Temperature Range
(-40°C to +85°C)
11 = 11mil Wafer Thickness
SS = SOIC
X = TSSOP
MA = 2.0mm x 3.0mm UDFN
C = VFBGA
WWU = Wafer Unsawn
AT24C256C-SSHL-B
Device Revision
Examples
Device Package Package
Drawing
Code
Package
Option
Shipping Carrier Option Device Grade
AT24C256CSSHLB SOIC SN SS Bulk (Tubes) Industrial
Temperature
(-40°C to +85°C)
AT24C256CSSHLT SOIC SN SS Tape and Reel
AT24C256CXHLT TSSOP ST X Tape and Reel
AT24C256CMAHLT UDFN Q4B MA Tape and Reel
AT24C256CMAHLE UDFN Q4B MA Extended Qty. Tape and
Reel
AT24C256CCULT VFBGA 8U21 C Tape and Reel
Microchip Devices Code Protection Feature
Note the following details of the code protection feature on Microchip devices:
Microchip products meet the specification contained in their particular Microchip Data Sheet.
Microchip believes that its family of products is one of the most secure families of its kind on the
market today, when used in the intended manner and under normal conditions.
There are dishonest and possibly illegal methods used to breach the code protection feature. All of
these methods, to our knowledge, require using the Microchip products in a manner outside the
operating specifications contained in Microchip’s Data Sheets. Most likely, the person doing so is
engaged in theft of intellectual property.
Microchip is willing to work with the customer who is concerned about the integrity of their code.
AT24C256C
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 36
Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their
code. Code protection does not mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the
code protection features of our products. Attempts to break Microchip’s code protection feature may be a
violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software
or other copyrighted work, you may have a right to sue for relief under that Act.
Legal Notice
Information contained in this publication regarding device applications and the like is provided only for
your convenience and may be superseded by updates. It is your responsibility to ensure that your
application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR
WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY
OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS
CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE.
Microchip disclaims all liability arising from this information and its use. Use of Microchip devices in life
support and/or safety applications is entirely at the buyers risk, and the buyer agrees to defend,
indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting
from such use. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual
property rights unless otherwise stated.
Trademarks
The Microchip name and logo, the Microchip logo, AnyRate, AVR, AVR logo, AVR Freaks, BitCloud,
chipKIT, chipKIT logo, CryptoMemory, CryptoRF, dsPIC, FlashFlex, flexPWR, Heldo, JukeBlox, KeeLoq,
Kleer, LANCheck, LINK MD, maXStylus, maXTouch, MediaLB, megaAVR, MOST, MOST logo, MPLAB,
OptoLyzer, PIC, picoPower, PICSTART, PIC32 logo, Prochip Designer, QTouch, SAM-BA, SpyNIC, SST,
SST Logo, SuperFlash, tinyAVR, UNI/O, and XMEGA are registered trademarks of Microchip Technology
Incorporated in the U.S.A. and other countries.
ClockWorks, The Embedded Control Solutions Company, EtherSynch, Hyper Speed Control, HyperLight
Load, IntelliMOS, mTouch, Precision Edge, and Quiet-Wire are registered trademarks of Microchip
Technology Incorporated in the U.S.A.
Adjacent Key Suppression, AKS, Analog-for-the-Digital Age, Any Capacitor, AnyIn, AnyOut, BodyCom,
CodeGuard, CryptoAuthentication, CryptoAutomotive, CryptoCompanion, CryptoController, dsPICDEM,
dsPICDEM.net, Dynamic Average Matching, DAM, ECAN, EtherGREEN, In-Circuit Serial Programming,
ICSP, INICnet, Inter-Chip Connectivity, JitterBlocker, KleerNet, KleerNet logo, memBrain, Mindi, MiWi,
motorBench, MPASM, MPF, MPLAB Certified logo, MPLIB, MPLINK, MultiTRAK, NetDetach, Omniscient
Code Generation, PICDEM, PICDEM.net, PICkit, PICtail, PowerSmart, PureSilicon, QMatrix, REAL ICE,
Ripple Blocker, SAM-ICE, Serial Quad I/O, SMART-I.S., SQI, SuperSwitcher, SuperSwitcher II, Total
Endurance, TSHARC, USBCheck, VariSense, ViewSpan, WiperLock, Wireless DNA, and ZENA are
trademarks of Microchip Technology Incorporated in the U.S.A. and other countries.
SQTP is a service mark of Microchip Technology Incorporated in the U.S.A.
Silicon Storage Technology is a registered trademark of Microchip Technology Inc. in other countries.
GestIC is a registered trademark of Microchip Technology Germany II GmbH & Co. KG, a subsidiary of
Microchip Technology Inc., in other countries.
All other trademarks mentioned herein are property of their respective companies.
AT24C256C
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 37
© 2018, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved.
ISBN: 978-1-5224-3374-3
Quality Management System Certified by DNV
ISO/TS 16949
Microchip received ISO/TS-16949:2009 certification for its worldwide headquarters, design and wafer
fabrication facilities in Chandler and Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures are for its PIC® MCUs and dsPIC®
DSCs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design and manufacture of development
systems is ISO 9001:2000 certified.
AT24C256C
© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 38
’8‘ MICFIDCHIP
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© 2018 Microchip Technology Inc. Datasheet DS20006042A-page 39

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