AT24C256BW-SH-T Equivalent & Substitute Parts

Part Overview

The AT24C256BW-SH-T is a 256Kbit EEPROM memory IC manufactured by Microchip Technology, featuring I2C interface operation at 1 MHz with 550 ns access time. This part is classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing system support and new design implementations. Substitute parts must maintain compatibility across memory capacity, interface protocol, electrical specifications, and physical packaging to ensure direct replacement capability.

Key Parameters

Parameter	AT24C256BW-SH-T
Memory Size	256Kbit
Memory Organization	32K x 8
Memory Interface	I2C
Clock Frequency	1 MHz
Access Time	550 ns
Write Cycle Time	5ms
Voltage Supply Range	1.8V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package / Case	8-SOIC (0.209", 5.30mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict adherence to the following parameters:

Memory Capacity & Organization: All substitutes must provide 256Kbit capacity in 32K x 8 organization
Interface Protocol: I2C interface is mandatory for all substitutes
Electrical Compatibility: Supply voltage range must encompass or match the original specification (1.8V ~ 5.5V minimum)
Operating Temperature Range: Must support -40°C ~ 85°C minimum
Write Cycle Time: 5ms specification must be maintained
Physical Package: 8-pin surface mount packages (SOIC or TSSOP variants) with compatible pinout
Compliance Standards: RoHS3 compliance required

Substitutes are grouped by clock frequency capability and access time performance, which determine system timing compatibility without affecting functional equivalence.

Parameter Comparison

Part Number	Manufacturer	Memory Size	Clock Frequency	Access Time	Voltage Supply	Operating Temp	Package	Product Status
AT24C256BW-SH-T	Microchip Technology	256Kbit	1 MHz	550 ns	1.8V ~ 5.5V	-40°C ~ 85°C	8-SOIC	Obsolete
24AA256-I/SM	Microchip Technology	256Kbit	400 kHz	900 ns	1.7V ~ 5.5V	-40°C ~ 85°C	8-SOIC	Active
24AA256T-E/SM	Microchip Technology	256Kbit	400 kHz	900 ns	1.7V ~ 5.5V	-40°C ~ 125°C	8-SOIC	Active
24AA256T-I/SM	Microchip Technology	256Kbit	400 kHz	900 ns	1.7V ~ 5.5V	-40°C ~ 85°C	8-SOIC	Active
24FC256T-I/SM	Microchip Technology	256Kbit	1 MHz	400 ns	1.7V ~ 5.5V	-40°C ~ 85°C	8-SOIC	Active
CAT24C256YIGT3JN	onsemi	256Kbit	1 MHz	500 ns	1.8V ~ 5.5V	-40°C ~ 85°C	8-TSSOP	Active
M24256-BRMN6P	STMicroelectronics	256Kbit	1 MHz	450 ns	1.8V ~ 5.5V	-40°C ~ 85°C	8-SOIC	Active
M24256-BRMN6TP	STMicroelectronics	256Kbit	1 MHz	450 ns	1.8V ~ 5.5V	-40°C ~ 85°C	8-SOIC	Active

Engineering Selection Recommendations

Primary Substitutes (Highest Compatibility)

24FC256T-I/SM and M24256-BRMN6TP are the preferred substitutes. Both maintain 1 MHz clock frequency operation matching the original part's timing specification, ensuring no system redesign is required. Both are active products with verified programmability status and full RoHS3 compliance. M24256-BRMN6TP offers the largest available inventory (30,200 units) with Cut Tape & Digi-Reel packaging for production environments.

Secondary Substitutes (Reduced Clock Frequency)

24AA256-I/SM, 24AA256T-E/SM, and 24AA256T-I/SM operate at 400 kHz, reducing I2C bus speed by 60% relative to the original specification. These substitutes are suitable only for applications where reduced clock frequency is acceptable. 24AA256T-E/SM extends operating temperature to -40°C ~ 125°C, providing enhanced thermal range for specific environmental requirements.

Alternative Package Option

CAT24C256YIGT3JN from onsemi provides 1 MHz operation in 8-TSSOP package format. This substitute is applicable only when TSSOP package geometry is compatible with PCB layout constraints. The 8-TSSOP package (0.173", 4.40mm width) is narrower than 8-SOIC variants, requiring physical footprint verification.

Compliance & Availability

All listed substitutes maintain RoHS3 compliance and REACH unaffected status. All are classified as active products with current manufacturing support, ensuring long-term availability and supply chain stability.

Frequently Asked Questions (FAQ)

Q: Can 24AA256-I/SM directly replace AT24C256BW-SH-T in existing designs?

A: Functional replacement is possible, but system timing must be evaluated. The 24AA256-I/SM operates at 400 kHz versus the original 1 MHz specification. If the application firmware or hardware timing loops depend on 1 MHz I2C bus speed, this substitute requires system validation. If the application uses standard I2C timing with no speed-critical dependencies, this part is compatible.

Q: What is the difference between 24AA256T-E/SM and 24AA256T-I/SM?

A: Both parts are identical except for operating temperature range. 24AA256T-E/SM supports -40°C ~ 125°C, while 24AA256T-I/SM supports -40°C ~ 85°C. Select 24AA256T-E/SM only if extended high-temperature operation is required.

Q: Is CAT24C256YIGT3JN a suitable substitute if my PCB uses 8-SOIC footprint?

A: No. CAT24C256YIGT3JN uses 8-TSSOP package, which has different pinout and physical dimensions than 8-SOIC. PCB footprint redesign is required. Use this part only if your design can accommodate TSSOP package geometry.

Q: Which substitute offers the best access time performance?

A: 24FC256T-I/SM provides 400 ns access time, the fastest among all substitutes. M24256-BRMN6P and M24256-BRMN6TP both provide 450 ns access time. The original AT24C256BW-SH-T specified 550 ns, so all listed substitutes improve access time performance.

Q: Are all substitutes RoHS3 compliant?

A: Yes. All listed substitute parts maintain RoHS3 compliance and REACH unaffected status, matching the original part's environmental certification requirements.

Q: What packaging options are available for production quantities?

A: M24256-BRMN6TP is supplied in Cut Tape & Digi-Reel format with 30,200 units in stock, optimized for high-volume manufacturing. 24FC256T-I/SM is available in Cut Tape & Digi-Reel with 3,300 units. 24AA256-I/SM and M24256-BRMN6P are supplied in Tube packaging for smaller quantities.

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