July 2011 Doc ID 6757 Rev 24 1/41
1
M24256-BF M24256-BR M24256-BW
M24256-DR
256 Kbit serial I²C bus EEPROM
with three Chip Enable lines
Features
■Compatible with all I2C bus modes:
– 1 MHz Fast-mode Plus
– 400 kHz Fast mode
– 100 kHz Standard mode
■Memory array:
– 256 Kb (32 Kbytes) of EEPROM
– Page size: 64 bytes
■M24xxx- DR: additional Write lockable Page
(Identification page)
■Single supply voltage:
– 1.7 V to 5.5 V
– 1.8 V to 5.5 V
– 2.5 V to 5.5 V
■Noise suppression
– Schmitt trigger inputs
– Input noise filter
■Write
– Byte write within 5 ms
– Page write within 5 ms
■Random and sequential read modes
■Write protect of the whole memory array
■Enhanced ESD/latch-up protection
■More than 1 million write cycles
■More than 40-year data retention
■Packages
–ECOPACK
2® (RoHS compliant and
halogen-free)
TSSOP8 (DW)
SO8 (MN)
150 mils width
WLCSP (CS)
UFDFPN8 (MB)
2 × 3 mm (MLP)
www.st.com
Contents M24256-BF, M24256-BR, M24256-BW, M24256-DR
2/41 Doc ID 6757 Rev 24
Contents
1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Signal description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 Serial Clock (SCL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Serial Data (SDA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 Chip Enable (E0, E1, E2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4 Write Control (WC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.5 VSS ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.6 Supply voltage (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.6.1 Operating supply voltage VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.6.2 Power-up conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.6.3 Device reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.6.4 Power-down conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3 Device operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1 Start condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2 Stop condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3 Acknowledge bit (ACK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.4 Data input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.5 Addressing the memory array . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.6 Write operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.7 Byte Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.8 Page Write (memory array) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.9 Write Identification Page (M24256-D only) . . . . . . . . . . . . . . . . . . . . . . . . 16
3.10 Lock Identification Page (M24256-D only) . . . . . . . . . . . . . . . . . . . . . . . . 16
3.11 ECC (error correction code) and write cycling . . . . . . . . . . . . . . . . . . . . . 16
3.12 Minimizing system delays by polling on ACK . . . . . . . . . . . . . . . . . . . . . . 18
3.13 Read operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.14 Random Address Read (in memory array) . . . . . . . . . . . . . . . . . . . . . . . . 19
3.15 Current Address Read (in memory array) . . . . . . . . . . . . . . . . . . . . . . . . 20
3.16 Sequential Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.17 Reading the Identification Page (M24256-D only) . . . . . . . . . . . . . . . . . . 20
M24256-BF, M24256-BR, M24256-BW, M24256-DR Contents
Doc ID 6757 Rev 24 3/41
3.18 Reading the lock status (M24256-D only) . . . . . . . . . . . . . . . . . . . . . . . . 21
3.19 Acknowledge in Read mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4 Initial delivery state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5 Maximum rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6 DC and AC parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8 Part numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
List of tables M24256-BF, M24256-BR, M24256-BW, M24256-DR
4/41 Doc ID 6757 Rev 24
List of tables
Table 1. Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Table 2. Most significant address byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Table 3. Least significant address byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Table 4. Device select code (for memory array). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Table 5. Operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Table 6. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 7. Operating conditions (voltage range W) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 8. Operating conditions (voltage range R) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 9. Operating conditions (voltage range F) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 10. AC test measurement conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 11. Input parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Table 12. Memory cell characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Table 13. DC characteristics (voltage range W, device grade 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Table 14. DC characteristics (voltage range W, device grade 6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Table 15. DC characteristics (voltage range R) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Table 16. DC characteristics (voltage range F) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Table 17. 400 kHz AC characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Table 18. 1 MHz AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Table 19. SO8N – 8-lead plastic small outline, 150 mils body width, package mechanical data . . . . 31
Table 20. TSSOP8 – 8-lead thin shrink small outline, package mechanical data. . . . . . . . . . . . . . . . 32
Table 21. UFDFPN8 (MLP8) 8-lead ultra thin fine pitch dual flat package no lead
2 x 3 mm, data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Table 22. WLCSP 0.5 mm pitch, package mechanical data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Table 23. Ordering information scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Table 24. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
M24256-BF, M24256-BR, M24256-BW, M24256-DR List of figures
Doc ID 6757 Rev 24 5/41
List of figures
Figure 1. Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 2. Package connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 3. WLCSP connections (top view, marking side, with balls on the underside) . . . . . . . . . . . . 7
Figure 4. Device select code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 5. I2C Fast mode (fC = 400 kHz): maximum Rbus value versus
bus parasitic capacitance (Cbus) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 6. I2C Fast mode Plus (fC = 1 MHz): maximum Rbus value versus
bus parasitic capacitance (Cbus) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 7. I2C bus protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 8. Write mode sequences with WC = 1 (data write inhibited) . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 9. Write mode sequences with WC = 0 (data write enabled) . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 10. Write cycle polling flowchart using ACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Figure 11. Read mode sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 12. AC test measurement I/O waveform. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Figure 13. AC waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 14. SO8N – 8-lead plastic small outline, 150 mils body width, package outline . . . . . . . . . . . . 31
Figure 15. TSSOP8 – 8-lead thin shrink small outline, package outline . . . . . . . . . . . . . . . . . . . . . . . 32
Figure 16. UFDFPN8 (MLP8) 8-lead ultra thin fine pitch dual flat package no lead
2 x 3 mm, outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 17. WLCSP, 0.5 mm pitch, package outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Description M24256-BF, M24256-BR, M24256-BW, M24256-DR
6/41 Doc ID 6757 Rev 24
1 Description
The M24256-Bx devices are I2C-compatible electrically erasable programmable memories
(EEPROM). They are organized as 32 K × 8 bits.
The M24256-DR is also an I2C-compatible EEPROM organized as 32 K × 8 bits, but it offers
an additional page, named the Identification Page (64 bytes). The Identification Page can be
used to store sensitive application parameters which can be (later) permanently locked in
read-only mode.
Figure 1. Logic diagram
Figure 2. Package connections
1. See Package mechanical data section for package dimensions, and how to identify pin-1.
Table 1. Signal names
Signal name Function Direction
E0, E1, E2 Chip Enable Inputs
SDA Serial Data I/O
SCL Serial Clock Input
WC Write Control Input
VCC Supply voltage
VSS Ground
!)G
3$!
6##
-XXX
7#
3#,
633
%%
1
AI04035e
2
3
4
8
7
6
5SDAVSS
SCL
WCE1
E0 VCC
E2
M24256-BF, M24256-BR, M24256-BW, M24256-DR Description
Doc ID 6757 Rev 24 7/41
Figure 3. WLCSP connections (top view, marking side, with balls on the underside)
Caution: As EEPROM cells loose their charge (and so their binary value) when exposed to ultra violet
(UV) light, EEPROM dice delivered in wafer form or in WLCSP package by
STMicroelectronics must never be exposed to UVlight.
V
CC
E1
SDA
SCL V
SS
WC
E0
E2
ai14712
Signal description M24256-BF, M24256-BR, M24256-BW, M24256-DR
8/41 Doc ID 6757 Rev 24
2 Signal description
2.1 Serial Clock (SCL)
This input signal is used to strobe all data in and out of the device. In applications where this
signal is used by slave devices to synchronize the bus to a slower clock, the bus master
must have an open drain output, and a pull-up resistor must be connected from Serial Clock
(SCL) to VCC. (Figure 6 indicates how the value of the pull-up resistor can be calculated). In
most applications, though, this method of synchronization is not employed, and so the pull-
up resistor is not necessary, provided that the bus master has a push-pull (rather than open
drain) output.
2.2 Serial Data (SDA)
This bidirectional signal is used to transfer data in or out of the device. It is an open drain
output that may be wire-OR’ed with other open drain or open collector signals on the bus. A
pull up resistor must be connected from Serial Data (SDA) to VCC. (Figure 6 indicates how
the value of the pull-up resistor can be calculated).
2.3 Chip Enable (E0, E1, E2)
These input signals are used to set the value that is to be looked for on the three least
significant bits (b3, b2, b1) of the 7-bit device select code. These inputs must be tied to VCC
or VSS, to establish the device select code. When not connected (left floating), these inputs
are read as Low (0,0,0).
Figure 4. Device select code
2.4 Write Control (WC)
This input signal is useful for protecting the entire contents of the memory from inadvertent
write operations. Write operations are disabled to the entire memory array when Write
Control (WC) is driven High. When unconnected, the signal is internally read as VIL, and
Write operations are allowed.
When Write Control (WC) is driven High, device select and address bytes are
acknowledged, Data bytes are not acknowledged.
Ai12806
VCC
M24xxx
VSS
Ei
VCC
M24xxx
VSS
Ei
M24256-BF, M24256-BR, M24256-BW, M24256-DR Signal description
Doc ID 6757 Rev 24 9/41
2.5 VSS ground
VSS is the reference for the VCC supply voltage.
2.6 Supply voltage (VCC)
2.6.1 Operating supply voltage VCC
Prior to selecting the memory and issuing instructions to it, a valid and stable VCC voltage
within the specified [VCC(min), VCC(max)] range must be applied (see Ta b l e 7 , Ta b le 8 and
Ta bl e 9 ). In order to secure a stable DC supply voltage, it is recommended to decouple the
VCC line with a suitable capacitor (usually of the order of 10 nF to 100 nF) close to the
VCC/VSS package pins.
This voltage must remain stable and valid until the end of the transmission of the instruction
and, for a Write instruction, until the completion of the internal write cycle (tW).
2.6.2 Power-up conditions
VCC has to rise continuously from 0 V up to VCC(min) (see Ta bl e 7 , Ta b l e 8 and Ta bl e 9 ),
and the rise time must not vary faster than 1 V/µs.
2.6.3 Device reset
In order to prevent inadvertent write operations during power-up, a power on reset (POR)
circuit is included. At power-up, the device does not respond to any instruction until VCC
reaches an internal reset threshold voltage. This threshold is lower than the minimum VCC
operating voltage defined in Ta bl e 7 , Ta b l e 8 and Ta bl e 9 .
When VCC passes over the POR threshold, the device is reset and enters the Standby
Power mode. However, the device must not be accessed until VCC reaches a valid and
stable VCC voltage within the specified [VCC(min), VCC(max)] range.
In a similar way, during power-down (continuous decrease in VCC), as soon as VCC drops
below the power on reset threshold voltage, the device stops responding to any instruction
sent to it.
2.6.4 Power-down conditions
During power-down (where VCC decreases continuously), the device must be in the Standby
Power mode (mode reached after decoding a Stop condition, assuming that there is no
internal Write cycle in progress).
Signal description M24256-BF, M24256-BR, M24256-BW, M24256-DR
10/41 Doc ID 6757 Rev 24
Figure 5. I2C Fast mode (fC = 400 kHz): maximum Rbus value versus
bus parasitic capacitance (Cbus)
Figure 6. I2C Fast mode Plus (fC = 1 MHz): maximum Rbus value versus
bus parasitic capacitance (Cbus)
1
10
100
10 100 1000
Bus line capacitor (pF)
Bus line pull-up resistor
(k )
I²C bus
master M24xxx
Rbus
VCC
Cbus
SCL
SDA
ai14796b
Rbus × Cbus = 400 ns
Here Rbus × Cbus = 120 ns
4 kΩ
30 pF
1
10
100
10 100
Bus line capacitor (pF)
Bus line pull-up resistor (k )
ai14795d
I²C bus
master M24xxx
R
bus
V
CC
C
bus
SCL
SDA
Rbus × Cbus = 270 ns
When tLOW = 700 ns
(max possible value for
fC = 1 MHz), the Rbus × Cbus
time constant must be below
the 270 ns time constant line
represented on the left.
When tLOW = 400 ns
(min value for fC = 1 MHz),
the Rbus × Cbus time constant
must be below the 100 ns
time constant line represented
on the left.
Here,
Rbus × Cbus = 150 ns
Rbus × Cbus = 100 ns
5
30
M24256-BF, M24256-BR, M24256-BW, M24256-DR Signal description
Doc ID 6757 Rev 24 11/41
Figure 7. I2C bus protocol
Table 2. Most significant address byte
b15 b14 b13 b12 b11 b10 b9 b8
Table 3. Least significant address byte
b7 b6 b5 b4 b3 b2 b1 b0
SCL
SDA
SCL
SDA
SDA
Start
condition
SDA
Input
SDA
Change
AI00792c
Stop
condition
123 789
MSB ACK
Start
condition
SCL 123 789
MSB ACK
Stop
condition
Device operation M24256-BF, M24256-BR, M24256-BW, M24256-DR
12/41 Doc ID 6757 Rev 24
3 Device operation
The device supports the I2C protocol. This is summarized in Figure 7. Any device that sends
data on to the bus is defined to be a transmitter, and any device that reads the data to be a
receiver. The device that controls the data transfer is known as the bus master, and the
other as the slave device. A data transfer can only be initiated by the bus master, which will
also provide the serial clock for synchronization. The device is always slave in all
communications.
3.1 Start condition
Start is identified by a falling edge of Serial Data (SDA) while Serial Clock (SCL) is stable in
the High state. A Start condition must precede any data transfer instruction. The device
continuously monitors (except during a Write cycle) Serial Data (SDA) and Serial Clock
(SCL) for a Start condition.
3.2 Stop condition
Stop is identified by a rising edge of Serial Data (SDA) while Serial Clock (SCL) is stable
and driven High. A Stop condition terminates communication between the device and the
bus master. A Read instruction that is followed by NoAck can be followed by a Stop
condition to force the device into the Standby mode. A Stop condition at the end of a Write
instruction triggers the internal Write cycle.
3.3 Acknowledge bit (ACK)
The acknowledge bit is used to indicate a successful byte transfer. The bus transmitter,
whether it be bus master or slave device, releases Serial Data (SDA) after sending eight bits
of data. During the 9th clock pulse period, the receiver pulls Serial Data (SDA) Low to
acknowledge the receipt of the eight data bits.
3.4 Data input
During data input, the device samples Serial Data (SDA) on the rising edge of Serial Clock
(SCL). For correct device operation, Serial Data (SDA) must be stable during the rising edge
of Serial Clock (SCL), and the Serial Data (SDA) signal must change only when Serial Clock
(SCL) is driven Low.
M24256-BF, M24256-BR, M24256-BW, M24256-DR Device operation
Doc ID 6757 Rev 24 13/41
3.5 Addressing the memory array
To start communication between the bus master and the slave device, the bus master must
initiate a Start condition. Following this, the bus master sends the device select code, shown
in Ta b l e 4 (on Serial Data (SDA), most significant bit first).
The 4-bit device type identifier 1010b selects the memory array, the 4-bit device type
identifier 1011b selects the Identification page. A device select code handling a value
different than 1010b or 1011b is not acknowledged by the device.
Up to eight memory devices can be connected on a single I2C bus. Each one is given a
unique 3-bit code on the Chip Enable (E0, E1, E2) inputs. When the device select code is
received, the device only responds if the Chip Enable Address is the same as the value on
the Chip Enable (E0, E1, E2) inputs.
The 8th bit is the Read/Write bit (RW). This bit is set to 1 for Read and 0 for Write operations.
If a match occurs on the device select code, the corresponding device gives an
acknowledgment on Serial Data (SDA) during the 9th bit time. If the device does not match
the device select code, it deselects itself from the bus, and goes into Standby mode.
Table 4. Device select code (for memory array)
Device type identifier(1)
1. The most significant bit, b7, is sent first.
Chip Enable address(2)
2. E0, E1 and E2 are compared against the respective external pins on the memory device.
RW
b7 b6 b5 b4 b3 b2 b1 b0
Device select code
when addressing the
memory array
1010E2E1E0RW
Device select code
when accessing the
Identification page
1011E2E1E0RW
Table 5. Operating modes
Mode RW bit WC(1)
1. X = VIH or VIL.
Bytes Initial sequence
Current Address
Read 1 X 1 Start, device select, RW = 1
Random Address
Read
0X 1Start, device select, RW = 0, Address
1 X re-Start, device select, RW = 1
Sequential Read 1 X ≥ 1 Similar to Current or Random Address
Read
Byte Write 0 VIL 1 Start, device select, RW = 0
Page Write 0 VIL ≤ 64 Start, device select, RW = 0
Device operation M24256-BF, M24256-BR, M24256-BW, M24256-DR
14/41 Doc ID 6757 Rev 24
Figure 8. Write mode sequences with WC = 1 (data write inhibited)
Stop
Start
Byte Write Dev sel Byte addr Byte addr Data in
WC
Start
Page Write Dev sel Byte addr Byte addr Data in 1
WC
Data in 2
AI01120d
Page Write
(cont'd)
WC (cont'd)
Stop
Data in N
ACK ACK ACK NO ACK
R/W
ACK ACK ACK NO ACK
R/W
NO ACK NO ACK
M24256-BF, M24256-BR, M24256-BW, M24256-DR Device operation
Doc ID 6757 Rev 24 15/41
3.6 Write operations
Following a Start condition the bus master sends a device select code with the Read/Write
bit (RW) reset to 0. The device acknowledges this, as shown in Figure 9, and waits for two
address bytes. The device responds to each address byte with an acknowledge bit, and
then waits for the data byte.
Each data byte in the memory has a 16-bit (two byte wide) address. The most significant
byte (Ta b l e 2 ) is sent first, followed by the least significant byte (Ta b l e 3 ). Bits b15 to b0 form
the address of the byte in memory.
When the bus master generates a Stop condition immediately after a data byte Ack bit (in
the “10th bit” time slot), either at the end of a Byte Write or a Page Write, the internal Write
cycle is triggered. A Stop condition at any other time slot does not trigger the internal Write
cycle.
After the Stop condition, the delay tW, and the successful completion of a Write operation,
the device’s internal address counter is incremented automatically, to point to the next byte
address after the last one that was modified.
During the internal Write cycle, Serial Data (SDA) is disabled internally, and the device does
not respond to any requests.
If the Write Control input (WC) is driven High, the Write instruction is not executed and the
accompanying data bytes are not acknowledged, as shown in Figure 8.
3.7 Byte Write
After the device select code and the address bytes, the bus master sends one data byte. If
the addressed location is Write-protected, by Write Control (WC) being driven High, the
device replies with NoAck, and the location is not modified. If, instead, the addressed
location is not Write-protected, the device replies with Ack. The bus master terminates the
transfer by generating a Stop condition, as shown in Figure 9.
3.8 Page Write (memory array)
The Page Write mode allows up to 64 bytes to be written in a single Write cycle, provided
that they are all located in the same ‘row’ in the memory: that is, the most significant
memory address bits (b15-b6) are the same. If more bytes are sent than will fit up to the end
of the row, a condition known as ‘roll-over’ occurs. This should be avoided, as data starts to
become overwritten in an implementation dependent way.
The bus master sends from 1 to 64 bytes of data, each of which is acknowledged by the
device if Write Control (WC) is Low. If Write Control (WC) is High, the contents of the
addressed memory location are not modified, and each data byte is followed by a NoAck.
After each byte is transferred, the internal byte address counter (the 7 least significant
address bits only) is incremented. The transfer is terminated by the bus master generating a
Stop condition.
Device operation M24256-BF, M24256-BR, M24256-BW, M24256-DR
16/41 Doc ID 6757 Rev 24
3.9 Write Identification Page (M24256-D only)
The Identification Page (64 bytes) is an additional page which can be written and (later)
permanently locked in Read-only mode. The identification page is written by issuing a Write
Identification Page instruction. This instruction uses the same protocol and format as Page
Write (into memory array), except for the following differences:
●Device Type Identifier = 1011b
●MSB address bits A15/A6 are don't care except for address bit A10 which must be ‘0’.
LSB address bits A5/A0 define the byte address inside the identification page.
If the Identification page is locked, the data bytes transferred during the Write Identification
Page instruction are not acknowledged (NoAck).
3.10 Lock Identification Page (M24256-D only)
The Lock Identification Page instruction (Lock ID) permanently locks the Identification page
in read-only mode. The Lock ID instruction is similar to Byte Write (into memory array) with
the following specific conditions:
●Device Type Identifier = 1011b
●Address bit A10 must be ‘1’; all other address bits are don't care
●The data byte must be equal to the binary value xxxx xx1x, where x is don't care.
If the Identification Page is locked, the data bytes transferred during the ID Write instruction
are not acknowledged (NoAck).
3.11 ECC (error correction code) and write cycling
The M24256-Bx and M24256-D devices offer an ECC (error correction code) logic which
compares each 4-byte word with its six associated ECC EEPROM bits. As a result, if a
single bit out of 4 bytes of data happens to be erroneous during a Read operation, the ECC
detects it and replaces it by the correct value. The read reliability is therefore much improved
by the use of this feature.
Note however that even if a single byte has to be written, 4 bytes are internally modified
(plus the ECC bits), that is, the addressed byte is cycled together with the other three bytes
making up the word. It is therefore recommended to write data by word (4 bytes) at address
4*N (where N is an integer) in order to benefit from the larger amount of Write cycles.
The M24256-Bx and M24256-DR devices are qualified at 1 million (1 000 000) Write cycles,
using a cycling routine that writes to the device by multiples of 4-bytes.
M24256-BF, M24256-BR, M24256-BW, M24256-DR Device operation
Doc ID 6757 Rev 24 17/41
Figure 9. Write mode sequences with WC = 0 (data write enabled)
Stop
Start
Byte Write Dev sel Byte addr Byte addr Data in
WC
Start
Page Write Dev sel Byte addr Byte addr Data in 1
WC
Data in 2
AI01106d
Page Write
(cont'd)
WC (cont'd)
Stop
Data in N
ACK
R/W
ACK ACK ACK
ACK ACK ACK ACK
R/W
ACKACK
Device operation M24256-BF, M24256-BR, M24256-BW, M24256-DR
18/41 Doc ID 6757 Rev 24
Figure 10. Write cycle polling flowchart using ACK
3.12 Minimizing system delays by polling on ACK
During the internal Write cycle, the device disconnects itself from the bus, and writes a copy
of the data from its internal latches to the memory cells. The maximum Write time (tw) is
shown in tables17 and 18, but the typical time is shorter. To make use of this, a polling
sequence can be used by the bus master.
The sequence, as shown in Figure 10, is:
●Initial condition: a Write cycle is in progress.
●Step 1: the bus master issues a Start condition followed by a device select code (the
first byte of the new instruction).
●Step 2: if the device is busy with the internal Write cycle, no Ack will be returned and
the bus master goes back to Step 1. If the device has terminated the internal Write
cycle, it responds with an Ack, indicating that the device is ready to receive the second
part of the instruction (the first byte of this instruction having been sent during Step 1).
Write cycle
in progress
AI01847d
Next
operation is
addressing the
memory
Start condition
Device select
with RW = 0
ACK
Returned
YES
NO
YESNO
ReStart
Stop
Data for the
Write operation
Device select
with RW = 1
Send Address
and Receive ACK
First byte of instruction
with RW = 0 already
decoded by the device
YESNO Start
condition
Continue the
Write operation
Continue the
Random Read operation
M24256-BF, M24256-BR, M24256-BW, M24256-DR Device operation
Doc ID 6757 Rev 24 19/41
3.13 Read operations
Read operations are performed independently of the state of the Write Control (WC) signal.
After the successful completion of a Read operation, the device’s internal address counter is
incremented by one, to point to the next byte address.
Figure 11. Read mode sequences
3.14 Random Address Read (in memory array)
A dummy Write is first performed to load the address into this address counter (as shown in
Figure 11) but without sending a Stop condition. Then, the bus master sends another Start
condition, and repeats the device select code, with the Read/Write bit (RW) set to 1. The
device acknowledges this, and outputs the contents of the addressed byte. The bus master
must not acknowledge the byte, and terminates the transfer with a Stop condition.
Start
Dev sel * Byte addr Byte addr
Start
Dev sel Data out 1
AI01105d
Data out N
Stop
Start
Current
Address
Read
Dev sel Data out
Random
Address
Read
Stop
Start
Dev sel * Data out
Sequential
Current
Read
Stop
Data out N
Start
Dev sel * Byte addr Byte addr
Sequential
Random
Read
Start
Dev sel * Data out 1
Stop
ACK
R/W
NO ACK
ACK
R/W
ACK ACK ACK
R/W
ACK ACK ACK NO ACK
R/W
NO ACK
ACK ACK ACK
R/W
ACK ACK
R/W
ACK NO ACK
Device operation M24256-BF, M24256-BR, M24256-BW, M24256-DR
20/41 Doc ID 6757 Rev 24
3.15 Current Address Read (in memory array)
For the Current Address Read operation, following a Start condition, the bus master only
sends a device select code with the Read/Write bit (RW) set to 1. The device acknowledges
this, and outputs the byte addressed by the internal address counter. The counter is then
incremented. The bus master terminates the transfer with a Stop condition, as shown in
Figure 11, without acknowledging the byte.
3.16 Sequential Read
This operation can be used after a Current Address Read or a Random Address Read. The
bus master does acknowledge the data byte output, and sends additional clock pulses so
that the device continues to output the next byte in sequence. To terminate the stream of
bytes, the bus master must not acknowledge the last byte, and must generate a Stop
condition, as shown in Figure 11.
The output data comes from consecutive addresses, with the internal address counter
automatically incremented after each byte output. After the last memory address, the
address counter ‘rolls-over’, and the device continues to output data from memory address
00h.
3.17 Reading the Identification Page (M24256-D only)
The Identification Page (64 bytes) is an additional page which can be written and (later)
permanently locked in Read-only mode.
The Identification Page can be read by issuing a Read Identification Page instruction. This
instruction uses the same protocol and format as the Random Address Read (from memory
array) with device type identifier defined as 1011b. The MSB address bits A17/A6 are don't
care, the LSB address bits A5/A0 define the byte address inside the Identification Page. The
number of bytes to read in the ID page must not exceed the page boundary, otherwise
unexpected data will be read (e.g.: when reading the Identification Page from location 10d,
the number of bytes should be less than or equal to 54, as the ID page boundary is
64 bytes).
M24256-BF, M24256-BR, M24256-BW, M24256-DR Device operation
Doc ID 6757 Rev 24 21/41
3.18 Reading the lock status (M24256-D only)
The locked/unlocked status of the Identification page can be checked by transmitting a
specific truncated command [Identification Page Write instruction + one data byte] to the
device. The device will return an acknowledge bit if the Identification page is unlocked,
otherwise a NoAck bit if the Identification page is locked.
Right after this, it is recommended to transmit to the device a Start condition followed by a
Stop condition, so that:
●Start: the truncated command is not executed because the Start condition resets the
device internal logic,
●Stop: the device is then set back into Standby mode by the Stop condition.
3.19 Acknowledge in Read mode
For all Read instructions, the device waits, after each byte read, for an acknowledgment
during the 9th bit time. If the bus master does not drive Serial Data (SDA) Low during this
time, the device terminates the data transfer and switches to its Standby mode.
Initial delivery state M24256-BF, M24256-BR, M24256-BW, M24256-DR
22/41 Doc ID 6757 Rev 24
4 Initial delivery state
The device is delivered with all bits in the memory array set to 1 (each byte contains FFh).
5 Maximum rating
Stressing the device outside the ratings listed in Ta bl e 6 may cause permanent damage to
the device. These are stress ratings only, and operation of the device at these, or any other
conditions outside those indicated in the operating sections of this specification, is not
implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Table 6. Absolute maximum ratings
Symbol Parameter Min. Max. Unit
Ambient Temperature with power applied –40 130 °C
TSTG Storage temperature –65 150 °C
TLEAD Lead temperature during soldering See note (1)
1. Compliant with JEDEC Std J-STD-020 (for small body, Sn-Pb or Pb assembly), the ST ECOPACK®
7191395 specification, and the European directive on the restriction of the use of certain hazardous
substances in electrical and electronic equipment (RoHS) 2002/95/EC.
°C
VIO Input or output range –0.50 6.5 V
VCC Supply voltage –0.50 6.5 V
IOL DC output current (SDA = 0) 5 mA
VESD Electrostatic pulse voltage (Human Body Model) (2)
2. Positive and negative pulses applied on pin pairs, according to AEC-Q100-002 (compliant with JEDEC Std
JESD22-A114, C1 = 100 pF, R1 = 1500 Ω, R2 = 500 Ω)
3000 V
M24256-BF, M24256-BR, M24256-BW, M24256-DR DC and AC parameters
Doc ID 6757 Rev 24 23/41
6 DC and AC parameters
This section summarizes the operating and measurement conditions, and the dc and ac
characteristics of the device. The parameters in the DC and AC characteristic tables that
follow are derived from tests performed under the measurement conditions summarized in
the relevant tables. Designers should check that the operating conditions in their circuit
match the measurement conditions when relying on the quoted parameters.
Figure 12. AC test measurement I/O waveform
Table 7. Operating conditions (voltage range W)
Symbol Parameter Min. Max. Unit
VCC Supply voltage 2.5 5.5 V
TA
Ambient operating temperature (device grade 6) –40 85 °C
Ambient operating temperature (device grade 3) –40 125 °C
Table 8. Operating conditions (voltage range R)
Symbol Parameter Min. Max. Unit
VCC Supply voltage 1.8 5.5 V
TAAmbient operating temperature –40 85 °C
Table 9. Operating conditions (voltage range F)
Symbol Parameter Min. Max. Unit
VCC Supply voltage 1.7 5.5 V
TAAmbient operating temperature –40 85 °C
Table 10. AC test measurement conditions
Symbol Parameter Min. Max. Unit
Cbus Load capacitance 100 pF
SCL input rise/fall time
SDA input fall time 50 ns
Input levels 0.2VCC to 0.8VCC V
Input and output timing reference levels 0.3VCC to 0.7VCC V
AI00825B
0.8VCC
0.2VCC
0.7VCC
0.3VCC
Input and Output
Timing Reference Levels
Input Levels
DC and AC parameters M24256-BF, M24256-BR, M24256-BW, M24256-DR
24/41 Doc ID 6757 Rev 24
Note: This parameter is not tested but established by characterization and qualification. To
estimate endurance in a specific application, please refer to AN2014.
Table 11. Input parameters
Symbol Parameter(1)
1. Sampled only, not 100% tested.
Test condition Min. Max. Unit
CIN Input capacitance (SDA) 8 pF
CIN Input capacitance (other pins) 6 pF
ZL(2)
2. E2,E1,E0: Input impedance when the memory is selected (after a Start condition).
Input impedance
(E2, E1, E0, WC)VIN < 0.3VCC 30 kΩ
ZH(2) Input impedance
(E2, E1, E0, WC)VIN > 0.7VCC 500 kΩ
Table 12. Memory cell characteristics
Symbol Parameter Test condition Min. Max. Unit
Ncycle Endurance TA = 25°C, 1.8V < Vcc < 5.5V 1,000,000 - Write cycle
Table 13. DC characteristics (voltage range W, device grade 3)
Symbol Parameter Test conditions (in addition to
those in Tabl e 7 and Tabl e 10)Min. Max. Unit
ILI
Input leakage current
(SCL, SDA, E0, E1, E2)
VIN = VSS or VCC
device in Standby mode ± 2 µA
ILO Output leakage current SDA in Hi-Z, external voltage
applied on SDA: VSS or VCC
± 2 µA
ICC Supply current (Read) fc = 400 kHz 2 mA
ICC0 Supply current (Write) During tW5(1)
1. Characterized value, not tested in production.
mA
ICC1 Standby supply current Device not selected(2), VIN = VSS
or VCC
2. The device is not selected after power-up, after a Read instruction (after the Stop condition), or after the
completion of the internal write cycle tW (tW is triggered by the correct decoding of a Write instruction).
5µA
VIL
Input low voltage
(SCL, SDA, WC) –0.45 0.3 VCC V
VIH
Input high voltage
(SCL, SDA) 0.7VCC 6.5 V
Input high voltage
(WC, E0, E1, E2) 0.7VCC VCC+0.6 V
VOL Output low voltage IOL = 2.1 mA, VCC = 2.5 V or
IOL = 3 mA, VCC = 5.5 V 0.4 V
M24256-BF, M24256-BR, M24256-BW, M24256-DR DC and AC parameters
Doc ID 6757 Rev 24 25/41
Table 14. DC characteristics (voltage range W, device grade 6)
Symbol Parameter Test conditions (see Ta ble 7 and
Table 1 0 )Min. Max. Unit
ILI
Input leakage
current
(SCL, SDA, E0, E1,
E2)
VIN = VSS or VCC
device in Standby mode ± 2 µA
ILO
Output leakage
current
SDA in Hi-Z, external voltage applied on
SDA: VSS or VCC
± 2 µA
ICC
Supply current
(Read)
VCC = 2.5 V, fc = 400 kHz
(rise/fall time < 50 ns) 1mA
VCC = 5.5 V, fc = 400 kHz
(rise/fall time < 50 ns) 2mA
2.5 V < VCC < 5.5 V, fc = 1 MHz(1)
(rise/fall time < 50 ns)
1. Only for devices operating at fC max = 1 MHz (see Table 18).
2.5 mA
ICC0
Supply current
(Write) During tW, 2.5 V < VCC < 5.5 V 2(2)
2. Characterized value, not tested in production.
mA
ICC1
Standby supply
current
Device not selected(3), VIN = VSS or VCC,
VCC = 2.5 V
3. The device is not selected after power-up, after a Read instruction (after the Stop condition), or after the
completion of the internal write cycle tW (tW is triggered by the correct decoding of a Write instruction).
2µA
Device not selected(3), VIN = VSS or VCC,
VCC = 5.5 V 3µA
VIL
Input low voltage
(SCL, SDA, WC) –0.45 0.3VCC V
VIH
Input high voltage
(SCL, SDA) 0.7VCC 6.5
V
Input high voltage
(WC, E0, E1, E2) 0.7VCC VCC+0.6
VOL Output low voltage IOL = 2.1 mA, VCC = 2.5 V or
IOL = 3 mA, VCC = 5.5 V 0.4 V
DC and AC parameters M24256-BF, M24256-BR, M24256-BW, M24256-DR
26/41 Doc ID 6757 Rev 24
Table 15. DC characteristics (voltage range R)
Symbol Parameter
Test conditions(1) (in addition
to those in Tabl e 8 and
Table 1 0 )
1. If the application uses the voltage range R device with 2.5 V < Vcc < 5.5 V and -40 °C < TA < +85 °C,
please refer to Table 14 instead of this table.
Min. Max. Unit
ILI
Input leakage current
(E1, E2, SCL, SDA)
VIN = VSS or VCC
device in Standby mode ± 2 µA
ILO Output leakage current SDA in Hi-Z, external voltage
applied on SDA: VSS or VCC
± 2 µA
ICC Supply current (Read)
VCC = 1.8 V, fc= 400 kHz 0.8 mA
fc= 1 MHz 2.5 mA
ICC0 Supply current (Write) During tW, 1.8 V < VCC < 2.5 V 2(2)
2. Characterized value, not tested in production
mA
ICC1 Standby supply current Device not selected(3),
VIN = VSS or VCC, VCC = 1.8 V
3. The device is not selected after power-up, after a Read instruction (after the Stop condition), or after the
completion of the internal write cycle tW (tW is triggered by the correct decoding of a Write instruction).
1µA
VIL
Input low voltage
(SCL, SDA, WC) 1.8 V ≤ V
CC < 2.5 V –0.45 0.25 VCC V
VIH
Input high voltage
(SCL, SDA) 1.8 V ≤ V
CC < 2.5 V 0.75VCC 6.5 V
Input high voltage
(WC, E0, E1, E2) 1.8 V ≤ V
CC < 2.5 V 0.75VCC VCC+0.6 V
VOL Output low voltage IOL = 1 mA, VCC = 1.8 V 0.2 V
M24256-BF, M24256-BR, M24256-BW, M24256-DR DC and AC parameters
Doc ID 6757 Rev 24 27/41
Table 16. DC characteristics (voltage range F)
Symbol Parameter Test conditions (in addition to
those in tables 9 and 10)(1)
1. If the application uses the voltage range F device with 2.5 V < Vcc < 5.5 V and -40 °C < TA < +85 °C,
please refer to Table 14 instead of this table.
Min. Max. Unit
ILI
Input leakage current
(E1, E2, SCL, SDA)
VIN = VSS or VCC
device in Standby mode ± 2 µA
ILO Output leakage current SDA in Hi-Z, external voltage
applied on SDA: VSS or VCC
± 2 µA
ICC Supply current (Read)
VCC = 1.7 V, fc= 400 kHz 0.8 mA
fc= 1 MHz 2.5 mA
ICC0 Supply current (Write) During tW, 1.7 V < VCC < 2.5 V 2(2)
2. Characterized value, not tested in production.
mA
ICC1 Standby supply current Device not selected(3),
VIN = VSS or VCC, VCC = 1.7 V
3. The device is not selected after power-up, after a Read instruction (after the Stop condition), or after the
completion of the internal write cycle tW (tW is triggered by the correct decoding of a Write instruction).
1µA
VIL
Input low voltage
(SCL, SDA, WC) 1.7 V ≤ V
CC < 2.5 V –0.45 0.25 VCC V
VIH
Input high voltage
(SCL, SDA) 1.7 V ≤ V
CC < 2.5 V 0.75VCC 6.5 V
Input high voltage
(WC, E0, E1, E2) 1.7 V ≤ V
CC < 2.5 V 0.75VCC VCC+0.6 V
VOL Output low voltage IOL = 1 mA, VCC = 1.7 V 0.2 V
DC and AC parameters M24256-BF, M24256-BR, M24256-BW, M24256-DR
28/41 Doc ID 6757 Rev 24
Table 17. 400 kHz AC characteristics
Test conditions specified in tables 7, 8, 9 and 10
Symbol Alt. Parameter Min.(1)
1. All values are referred to VIL(max) and VIH(min).
Max.(1) Unit
fCfSCL Clock frequency 400 kHz
tCHCL tHIGH Clock pulse width high 600 ns
tCLCH tLOW Clock pulse width low 1300 ns
tQL1QL2(2)
2. Characterized only, not tested in production.
tFSDA (out) fall time 20(3)
3. With Cbus = 10 pF.
120 ns
tXH1XH2 tRInput signal rise time (4)
4. There is no min. or max. values for the input signal rise and fall times. It is however recommended by the
I²C-bus specification that the input signal rise and fall times be more than 20 ns and less than 300 ns
when fC< 400 kHz.
(4) ns
tXL1XL2 tFInput signal fall time (4) (4) ns
tDXCX tSU:DAT Data in set up time 100 ns
tCLDX tHD:DAT Data in hold time 0 ns
tCLQX(5)
5. The I²C-bus specification does not define a min value of the data hold time (tHD;DAT). The min value of
tCLQX (Data out hold time) of the M24xxx devices offers a safe timing to bridge the undefined region of the
falling edge SCL.
tDH Data out hold time 100 ns
tCLQV (6)
6. tCLQV is the time (from the falling edge of SCL) required by the SDA bus line to reach either 0.3VCC or
0.7VCC, assuming that Rbus × Cbus time constant is within the values specified in Figure 5.
tAA Clock low to next data valid (access time) 900 ns
tCHDL tSU:STA Start condition setup time 600 ns
tDLCL tHD:STA Start condition hold time 600 ns
tCHDH tSU:STO Stop condition set up time 600 ns
tDHDL tBUF
Time between Stop condition and next Start
condition 1300 ns
tWtWR Write time 5 ms
tNS(7)
7. Characterized only, not tested in production.
Pulse width ignored (input filter on SCL and
SDA) 80 ns
M24256-BF, M24256-BR, M24256-BW, M24256-DR DC and AC parameters
Doc ID 6757 Rev 24 29/41
Table 18. 1 MHz AC characteristics(1)
1. Only new devices identified by the process letter K are qualified at 1 MHz (refer to TN0440 for more).
Test conditions specified in tables 7, 8, 9 and 10
Symbol Alt. Parameter Min.(2)
2. All values are referred to VIL(max) and VIH(min).
Max.(2) Unit
fCfSCL Clock frequency 0 1 MHz
tCHCL tHIGH Clock pulse width high 300 - ns
tCLCH tLOW Clock pulse width low 400 - ns
tXH1XH2 tRInput signal rise time (3)
3. There is no min. or max. values for the input signal rise and fall times. It is however recommended by the
I²C-bus specification that the input signal rise and fall times be less than 120 ns when fC<1MHz.
(3) ns
tXL1XL2 tFInput signal fall time (3) (3) ns
tQL1QL2(4)
4. Characterized only, not tested in production.
tFSDA (out) fall time(5)
5. With CL = 10 pF.
20 120 ns
tDXCX tSU:DAT Data in setup time 80 - ns
tCLDX tHD:DAT Data in hold time 0 - ns
tCLQX(6)
6. The I²C-bus specification does not define a min value of the data hold time (tHD;DAT). The min value of
tCLQX (Data out hold time) of the M24xxx devices offers a safe timing to bridge the undefined region of the
falling edge SCL.
tDH Data out hold time 50 - ns
tCLQV(7)
7. tCLQV is the time (from the falling edge of SCL) required by the SDA bus line to reach either 0.3VCC or
0.7VCC, assuming that Rbus × Cbus time constant is within the values specified in Figure 6.
tAA Clock low to next data valid (access time) 500 ns
tCHDL tSU:STA Start condition setup time 250 - ns
tDLCL tHD:STA Start condition hold time 250 - ns
tCHDH tSU:STO Stop condition setup time 250 - ns
tDHDL tBUF
Time between Stop condition and next
Start condition 500 - ns
tWtWR Write time - 5 ms
tNS(4) Pulse width ignored (input filter on SCL and
SDA) -50ns
DC and AC parameters M24256-BF, M24256-BR, M24256-BW, M24256-DR
30/41 Doc ID 6757 Rev 24
Figure 13. AC waveforms
3#,
3$!)N
3#,
3$!/UT
3#,
3$!)N
T#(#,
T$,#,
T#($,
3TART
CONDITION
T#,#(
T$8#(T#,$8
3$!
)NPUT
3$!
#HANGE
T#($( T$($,
3TOP
CONDITION
$ATAVALID
T#,16 T#,18
T#($(
3TOP
CONDITION
T#($,
3TART
CONDITION
7RITECYCLE
T7
!)F
3TART
CONDITION
T#(#,
T8(8(
T8(8(
T8,8,
T8,8,
$ATAVALID
T1,1,
M24256-BF, M24256-BR, M24256-BW, M24256-DR Package mechanical data
Doc ID 6757 Rev 24 31/41
7 Package mechanical data
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK® packages, depending on their level of environmental compliance. ECOPACK®
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK® is an ST trademark.
Figure 14. SO8N – 8-lead plastic small outline, 150 mils body width, package outline
1. Drawing is not to scale.
Table 19. SO8N – 8-lead plastic small outline, 150 mils body width, package
mechanical data
Symbol
millimeters inches(1)
1. Values in inches are converted from mm and rounded to four decimal digits.
Typ Min Max Typ Min Max
A 1.75 0.0689
A1 0.1 0.25 0.0039 0.0098
A2 1.25 0.0492
b 0.28 0.48 0.011 0.0189
c 0.17 0.23 0.0067 0.0091
ccc 0.1 0.0039
D 4.9 4.8 5 0.1929 0.1890 0.1969
E 6 5.8 6.2 0.2362 0.2283 0.2441
E1 3.9 3.8 4 0.1535 0.1496 0.1575
e 1.27 - - 0.05 - -
h 0.25 0.5 0.0098 0.0197
k 0°8° 0°8°
L 0.4 1.27 0.0157 0.05
L1 1.04 0.0409
SO-A
E1
8
ccc
b
e
A
D
c
1
E
h x 45˚
A2
k
0.25 mm
L
L1
A1
GAUGE PLANE
Package mechanical data M24256-BF, M24256-BR, M24256-BW, M24256-DR
32/41 Doc ID 6757 Rev 24
Figure 15. TSSOP8 – 8-lead thin shrink small outline, package outline
1. Drawing is not to scale.
Table 20. TSSOP8 – 8-lead thin shrink small outline, package mechanical data
Symbol
millimeters inches(1)
1. Values in inches are converted from mm and rounded to four decimal digits.
Typ Min Max Typ Min Max
A 1.200 0.0472
A1 0.050 0.150 0.0020 0.0059
A2 1.000 0.800 1.050 0.0394 0.0315 0.0413
b 0.190 0.300 0.0075 0.0118
c 0.090 0.200 0.0035 0.0079
CP 0.100 0.0039
D 3.000 2.900 3.100 0.1181 0.1142 0.1220
e 0.650 – – 0.0256 – –
E 6.400 6.200 6.600 0.2520 0.2441 0.2598
E1 4.400 4.300 4.500 0.1732 0.1693 0.1772
L 0.600 0.450 0.750 0.0236 0.0177 0.0295
L1 1.000 0.0394
α0° 8° 0° 8°
N8 8
TSSOP8AM
1
8
CP
c
L
EE1
D
A2A
α
eb
4
5
A1
L1
M24256-BF, M24256-BR, M24256-BW, M24256-DR Package mechanical data
Doc ID 6757 Rev 24 33/41
Figure 16. UFDFPN8 (MLP8) 8-lead ultra thin fine pitch dual flat package no lead
2 x 3 mm, outline
1. Drawing is not to scale.
2. The central pad (the area E2 by D2 in the above illustration) is pulled, internally, to VSS. It must not be
allowed to be connected to any other voltage or signal line on the PCB, for example during the soldering
process.
3. The circle in the top view of the package indicates the position of pin 1.
Table 21. UFDFPN8 (MLP8) 8-lead ultra thin fine pitch dual flat package no lead
2 x 3 mm, data
Symbol
millimeters inches(1)
1. Values in inches are converted from mm and rounded to four decimal digits.
Typ Min Max Typ Min Max
A 0.55 0.45 0.6 0.0217 0.0177 0.0236
A1 0.02 0 0.05 0.0008 0 0.002
b 0.25 0.2 0.3 0.0098 0.0079 0.0118
D 2 1.9 2.1 0.0787 0.0748 0.0827
D2 1.6 1.5 1.7 0.063 0.0591 0.0669
E 3 2.9 3.1 0.1181 0.1142 0.122
E2 0.2 0.1 0.3 0.0079 0.0039 0.0118
e 0.5 - - 0.0197 - -
L 0.45 0.4 0.5 0.0177 0.0157 0.0197
L1 0.15 0.0059
L3 0.3 0.0118
ddd(2)
2. Applied for exposed die paddle and terminals. Exclude embedding part of exposed die paddle from
measuring.
0.08 0.08
D
E
UFDFPN-01
A
A1
ddd
L1
eb
D2
L
E2
L3
Package mechanical data M24256-BF, M24256-BR, M24256-BW, M24256-DR
34/41 Doc ID 6757 Rev 24
Figure 17. WLCSP, 0.5 mm pitch, package outline
1. Drawing is not to scale.
Table 22. WLCSP 0.5 mm pitch, package mechanical data(1)
1. Preliminary data.
Symbol
Millimeters Inches(2)
2. Values in inches are converted from mm and rounded to four decimal digits.
Typ Min Max Typ Min Max
A 0.60 0.55 0.65 0.0236 0.0217 0.0256
A1 0.245 0.22 0.27 0.0096 0.0087 0.0106
A2 0.355 0.330 0.380 0.0140 0.0130 0.0150
B Ø 0.311 Ø 0.0122
D 1.97 1.95 1.99 0.0776 0.0768 0.0783
E 1.785 1.765 1.805 0.0703 0.0695 0.0711
e 0.5 0.0197
e1 0.866 0.0341
e2 0.25 0.0098
e3 0.433 0.0170
F 0.552 0.502 0.602 0.0217 0.0198 0.0237
G 0.392 0.342 0.442 0.0154 0.0135 0.0174
N(3)
3. N is the total number of terminals.
8 8
D
E
e2
G
321
B
e
A
B
C
D
E
Fe3
e1
Orientation reference
A1
A
A2
M24256-BF, M24256-BR, M24256-BW, M24256-DR Part numbering
Doc ID 6757 Rev 24 35/41
8 Part numbering
For a list of available options (speed, package, etc.) or for further information on any aspect
of this device, please contact your nearest ST sales office.
Table 23. Ordering information scheme
Example: M24256–B W MW 6 T P /AB
Device type
M24 = I2C serial access EEPROM
Device function
256– = 256 Kbit (32 Kb × 8)
Device family
B: Without Identification page
D: With additional Identification page
Operating voltage
W = VCC = 2.5 to 5.5 V
R = VCC = 1.8 to 5.5 V
F = VCC = 1.7 to 5.5 V
Package
MN = SO8 (150 mils body width)
DW = TSSOP8
MB = UFDFPN8 (MLP8)
CS = WLCSP
Device grade
6 = Industrial temperature range, –40 to 85 °C. Device tested with standard test flow
3 = Automotive: device tested with high reliability certified flow(1)
over –40 to 125 °C
Option
blank = standard packing
T = tape and reel packing
Plating technology
P or G = ECOPACK® (RoHS compliant)
Process
/A = F8L process (for WLCSP package ordering only)
/AB = F8L process (for device grade 3 ordering only)
1. ST strongly recommends the use of the Automotive Grade devices for use in an automotive environment. The High
Reliability Certified Flow (HRCF) is described in the quality note QNEE9801. Please ask your nearest ST sales office for a
copy.
Revision history M24256-BF, M24256-BR, M24256-BW, M24256-DR
36/41 Doc ID 6757 Rev 24
9 Revision history
Table 24. Document revision history
Date Revision Changes
29-Jan-2001 1.1
Lead Soldering Temperature in the Absolute Maximum Ratings table
amended
Write Cycle Polling Flow Chart using ACK illustration updated
LGA8 and SO8(wide) packages added
References to PSDIP8 changed to PDIP8, and Package Mechanical data
updated
10-Apr-2001 1.2 LGA8 Package Mechanical data and illustration updated
SO16 package removed
16-Jul-2001 1.3 LGA8 Package given the designator “LA”
02-Oct-2001 1.4 LGA8 Package mechanical data updated
13-Dec-2001 1.5
Document becomes Preliminary Data
Test conditions for ILI, ILO, ZL and ZH made more precise
VIL and VIH values unified. tNS value changed
12-Jun-2001 1.6 Document promoted to Full Datasheet
22-Oct-2003 2.0
Table of contents, and Pb-free options added. Minor wording changes in
Summary Description, Power-On Reset, Memory Addressing, Write
Operations, Read Operations. VIL(min) improved to –0.45V.
02-Sep-2004 3.0
LGA8 package is Not for New Design. 5V and -S supply ranges, and
Device Grade 5 removed. Absolute Maximum Ratings for VIO(min) and
VCC(min) changed. Soldering temperature information clarified for RoHS
compliant devices. Device grade information clarified. AEC-Q100-002
compliance. VIL specification unified for SDA, SCL and WC
22-Feb-2005 4.0
Initial delivery state is FFh (not necessarily the same as Erased).
LGA package removed, TSSOP8 and SO8N packages added (see
Package mechanical data section and Table 23: Ordering information
scheme).
Voltage range R (1.8V to 5.5V) also offered. Minor wording changes.
ZL Test Conditions modified in Table 11: Input parameters and Note 2
added.
ICC and ICC1 values for VCC = 5.5V added to Table 13: DC characteristics
(voltage range W).
Note added to Table 13: DC characteristics (voltage range W).
Power On Reset paragraph specified.
tW max value modified in Table 16: 400 kHz AC characteristics and note 4
added. Plating technology changed in Table 23: Ordering information
scheme.
Resistance and capacitance renamed in Figure 6.
M24256-BF, M24256-BR, M24256-BW, M24256-DR Revision history
Doc ID 6757 Rev 24 37/41
05-May-2006 5
Power On Reset paragraph replaced by Section 2.6: Supply voltage
(VCC). Figure 4: Device select code added.
ECC (error correction code) and write cycling added and specified at 1
Million cycles.
ICC0 added and ICC1 specified over the whole voltage range in Ta b l e 1 3
and Ta bl e 1 4 .
PDIP8 package removed. Packages are ECOPACK® compliant. Small
text changes.
16-Oct-2006 6
M24256-BW and M24256-BR part numbers added.
Section 3.11: ECC (error correction code) and write cycling updated.
ICC and ICC1 modified in Table 14: DC characteristics (voltage range R).
tW modified in Table 16: 400 kHz AC characteristics.
SO8Narrow package specifications updated (see Ta b l e 1 9 and
Figure 14). Blank option removed from below Plating technology in
Table 23: Ordering information scheme.
02-Jul-2007 7
Section 2.6: Supply voltage (VCC) modified.
Section 3.11: ECC (error correction code) and write cycling modified.
JEDEC standard and European directive references corrected below
Table 6: Absolute maximum ratings.
Rise/fall time conditions modified for ICC and VIH max modified in
Table 13: DC characteristics (voltage range W) and Table 14: DC
characteristics (voltage range R)
Note 1 removed from Table 13: DC characteristics (voltage range W).
SO8W package specifications modified in Section 7: Package mechanical
data.
Table 25: Available M24256-BR, M24256-BW, M24256-BF products
(package, voltage range, temperature grade) and Table 26: Available
M24512-x products (package, voltage range, temperature grade) added.
16-Oct-2007 8
Section 2.5: VSS ground added. Small text changes.
VIO max changed and Note 1 updated to latest standard revision in
Table 6: Absolute maximum ratings.
Note removed from Table 11: Input parameters.
VIH min and VIL max modified in Table 14: DC characteristics (voltage
range R).
Removed tCH1CH2, tCL1CL2 and tDH1DH2, and added tXL1XL2, tDL1DL2 and
Note 3 in Table 16: 400 kHz AC characteristics.
tXH1XH2, tXL1XL2 and Note 2 added to Table 17: 1 MHz AC characteristics.
Figure 13: AC waveforms modified.
Package mechanical data inch values calculated from mm and rounded to
4 decimal digits (see Section 7: Package mechanical data).
Table 24. Document revision history (continued)
Date Revision Changes
Revision history M24256-BF, M24256-BR, M24256-BW, M24256-DR
38/41 Doc ID 6757 Rev 24
14-Dec-2007 9
1 MHz frequency introduced (M24512-HR root part number).
Section 2.6.3: Device reset modified.
Figure 5: I2C Fast mode (fC = 400 kHz): maximum Rbus value versus bus
parasitic capacitance (Cbus) modified, Figure 6: I2C Fast mode Plus (fC =
1 MHz): maximum Rbus value versus bus parasitic capacitance (Cbus)
added.
tNS moved from Ta b l e 1 1 to Ta b l e 1 6 . ILO test conditions modified in
Ta b l e 1 3 .
Table 14: DC characteristics (voltage range R) and Table 17: 1 MHz AC
characteristics modified. Small text changes.
27-Mar-2008 10
Small text changes. M24256-BHR root part number added.
Section 2.6.3: Device reset on page 9 updated.
Figure 6: I2C Fast mode Plus (fC = 1 MHz): maximum Rbus value versus
bus parasitic capacitance (Cbus) on page 10 updated.
Caution removed in Section 3.11: ECC (error correction code) and write
cycling.
22-Apr-2008 11
M24512-W and M24256-BW offered in the device grade 3 option
(automotive temperature range):
–Table 7: Operating conditions (voltage range W),
–Table 13: DC characteristics (voltage range W),
– /AB Process letters added to Table 23: Ordering information scheme,
–Table 25: Available M24256-BR, M24256-BW, M24256-BF products
(package, voltage range, temperature grade) and
–Table 26: Available M24512-x products (package, voltage range,
temperature grade) updated accordingly).
Small text changes.
22-Dec-2008 12
WLCSP package added (see Figure 3: WLCSP connections (top view,
marking side, with balls on the underside) and Section 7: Package
mechanical data).
21-Jan-2009 13
M24256-BF part number added (VCC = 1.7 V to 5.5 V voltage range
added, see Ta b l e 9 , Tab l e 1 5 , Table 1 6 and Table 25 ).
ICC1 test conditions modified in Table 13: DC characteristics (voltage
range W), Table 14: DC characteristics (voltage range R) and Tabl e 15:
DC characteristics (voltage range F).
05-Jun-2009 14
M24512-DR part number and Identification page feature added.
Command replaced by instruction in the whole document.
UFDFPN8 added.
Figure 6 updated.
Section 2.6.2: Power-up conditions and Section 2.6.3: Device reset
updated.
tCLQX and tCLQV updated in Ta bl e 1 6 , Note 5 and Note 8 added.
tCLQX and tCLQV updated in Ta b l e 1 7 , Note 6 and Note 9 added.
Section 8: Part numbering updated.
Reference to the SURE program removed in Section 5: Maximum rating.
Previous 1 MHz M24512-HR and M24512-BHR devices replaced by new
M24512-R and M24256-BR (process letter K).
Table 24. Document revision history (continued)
Date Revision Changes
M24256-BF, M24256-BR, M24256-BW, M24256-DR Revision history
Doc ID 6757 Rev 24 39/41
16-Jun-2009 15 Part numbers updated in cover page header.
20-Aug-2009 16
IOL added to Table 7: Operating conditions (voltage range W).
Note 1and ICC modified in Table 13: DC characteristics (voltage range W);
Note and ICC modified in Table 14: DC characteristics (voltage range R);
13-Oct-2009 17
Datasheet split to leave only devices with 256 Kbit capacity.
M24256-DR part number added (see Table 26: Available M24256-DR
products (package, voltage range, temperature grade).
Figure 4: Device select code and Figure 5: I2C Fast mode (fC = 400 kHz):
maximum Rbus value versus bus parasitic capacitance (Cbus) updated.
VIO max modified in Table 6: Absolute maximum ratings.
VIH modified in Table 13: DC characteristics (voltage range W), Ta ble 1 4 :
DC characteristics (voltage range R) and Table 15: DC characteristics
(voltage range F).
In Table16: 400kHz AC characteristics and Table 17: 1 MHz AC
characteristics:
–t
DL1DL2 changed to tQL1QL2
–t
CHDX changed to tCHDL
–t
XH1XH2 and tXL1XL2 values removed
– Notes modified
Figure 13: AC waveforms modified.
05-Nov-2009 18
Section 3.9: Write Identification Page (M24256-D only)
corrected.Section 3.17: Reading the Identification Page (M24256-D only)
clarified.
10-Dec-2009 19
UFDFPN8 package is now offered (see Section 7: Package mechanical
data, Table 23: Ordering information scheme and Table 25: Available
M24256-BR, M24256-BW, M24256-BF products (package, voltage
range, temperature grade).
19-Jan-2010 20 Revision number corrected at bottom of pages.
04-Mar-2010 21 Process description corrected in Table 23: Ordering information scheme.
21-Dec-2010 22
Updated text in:
Features, Section 1: Description, Section 3.1: Start condition, Section 3.6:
Write operations, Section 3.9: Write Identification Page (M24256-D only),
Section 3.10: Lock Identification Page (M24256-D only), Section 3.11:
ECC (error correction code) and write cycling, Section 3.17: Reading the
Identification Page (M24256-D only), Section 3.18: Reading the lock
status (M24256-D only), Table 10: AC test measurement conditions,
Section 8: Part numbering.
Updated the following according to the I²C_bus specification:
Table 17: 400 kHz AC characteristics, Table 18: 1 MHz AC characteristics,
Figure 13: AC waveforms.
Table 24. Document revision history (continued)
Date Revision Changes
Revision history M24256-BF, M24256-BR, M24256-BW, M24256-DR
40/41 Doc ID 6757 Rev 24
14-Feb-2011 23
Added caution under Figure 3: WLCSP connections (top view, marking
side, with balls on the underside).
Updated:
–Description
–Section 3.5: Addressing the memory array
–Section 3.17: Reading the Identification Page (M24256-D only)
–Section 3.18: Reading the lock status (M24256-D only)
–Table 2: Most significant address byte
–Table 6: Absolute maximum ratings
–Table 17: 400 kHz AC characteristics
–Table 18: 1 MHz AC characteristics
Moved:
–Table 2: Most significant address byte from Section 2.6.4 to Section 3.5
Deleted:
–Table 3: Device select code to access the Identification page (M24256-
DR only)
– Table 25: Available M24256-BR, M24256-BW, M24256-BF products
(package, voltage range, temperature grade)
– Table 26: Available M24256-DR products (package, voltage range,
temperature grade)
05-Jul-2011 24
Added Table 12: Memory cell characteristics.
Updated:
–Section 1: Description
–Table 6: Absolute maximum ratings
–I
CC0 maximum value in Table 14: DC characteristics (voltage range W,
device grade 6), Table 15: DC characteristics (voltage range R) and
Table 16: DC characteristics (voltage range F)
Deleted all references to package SO8 (MW) 208 mils width.
Table 24. Document revision history (continued)
Date Revision Changes
M24256-BF, M24256-BR, M24256-BW, M24256-DR
Doc ID 6757 Rev 24 41/41
Please Read Carefully:
Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the
right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any
time, without notice.
All ST products are sold pursuant to ST’s terms and conditions of sale.
Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no
liability whatsoever relating to the choice, selection or use of the ST products and services described herein.
No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. If any part of this
document refers to any third party products or services it shall not be deemed a license grant by ST for the use of such third party products
or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoever of such
third party products or services or any intellectual property contained therein.
UNLESS OTHERWISE SET FORTH IN ST’S TERMS AND CONDITIONS OF SALE ST DISCLAIMS ANY EXPRESS OR IMPLIED
WARRANTY WITH RESPECT TO THE USE AND/OR SALE OF ST PRODUCTS INCLUDING WITHOUT LIMITATION IMPLIED
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS
OF ANY JURISDICTION), OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT.
UNLESS EXPRESSLY APPROVED IN WRITING BY AN AUTHORIZED ST REPRESENTATIVE, ST PRODUCTS ARE NOT
RECOMMENDED, AUTHORIZED OR WARRANTED FOR USE IN MILITARY, AIR CRAFT, SPACE, LIFE SAVING, OR LIFE SUSTAINING
APPLICATIONS, NOR IN PRODUCTS OR SYSTEMS WHERE FAILURE OR MALFUNCTION MAY RESULT IN PERSONAL INJURY,
DEATH, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE. ST PRODUCTS WHICH ARE NOT SPECIFIED AS "AUTOMOTIVE
GRADE" MAY ONLY BE USED IN AUTOMOTIVE APPLICATIONS AT USER’S OWN RISK.
Resale of ST products with provisions different from the statements and/or technical features set forth in this document shall immediately void
any warranty granted by ST for the ST product or service described herein and shall not create or extend in any manner whatsoever, any
liability of ST.
ST and the ST logo are trademarks or registered trademarks of ST in various countries.
Information in this document supersedes and replaces all information previously supplied.
The ST logo is a registered trademark of STMicroelectronics. All other names are the property of their respective owners.
© 2011 STMicroelectronics - All rights reserved
STMicroelectronics group of companies
Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan -
Malaysia - Malta - Morocco - Philippines - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America
www.st.com