25AA256-I/ST EEPROM Memory IC Equivalent & Substitute Parts

Part Overview

The 25AA256-I/ST is a 256Kbit Serial Peripheral Interface (SPI) EEPROM memory IC manufactured by Microchip Technology. This non-volatile memory device operates at 10 MHz clock frequency with a supply voltage range of 1.8V to 5.5V and is housed in an 8-TSSOP surface mount package. The part is currently in active production status with ROHS3 compliance and unlimited moisture sensitivity level (MSL 1). Substitute parts are necessary when addressing supply constraints, extended temperature requirements, higher clock frequency specifications, or automotive-grade qualifications.

Key Parameters

Parameter	Value
Memory Size	256Kbit
Memory Organization	32K x 8
Memory Interface	SPI
Clock Frequency	10 MHz
Write Cycle Time	5ms
Voltage Supply Range	1.8V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package Type	8-TSSOP (0.173", 4.40mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the 25AA256-I/ST is determined by strict equivalence in the following critical parameters:

Memory capacity: 256Kbit (32K x 8 organization)
Interface protocol: SPI
Package type: 8-TSSOP surface mount
Supply voltage compatibility: Minimum 1.8V support
Write cycle time: 5ms or faster

Substitute parts are grouped into three categories based on operational differences:

Category 1: Direct Equivalents (10 MHz Clock) Parts with identical 10 MHz clock frequency and -40°C to 85°C temperature range maintain full functional equivalence with the main part.

Category 2: Enhanced Performance (20 MHz Clock) Parts with 20 MHz clock frequency provide higher data throughput while maintaining all other electrical and mechanical specifications. These are backward compatible in applications not requiring the higher speed.

Category 3: Extended Temperature & Automotive Grade Parts qualified to -40°C to 125°C or -40°C to 105°C with AEC-Q100 automotive qualification support extended operating ranges and automotive applications.

Parameter Comparison

Part Number	Manufacturer	Clock Frequency	Voltage Supply	Operating Temperature	Write Cycle Time	Package	Automotive Grade
25AA256-I/ST	Microchip Technology	10 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	No
25AA256-E/ST	Microchip Technology	10 MHz	1.8V ~ 5.5V	-40°C ~ 125°C	5ms	8-TSSOP	No
AT25256B-XHL-B	Microchip Technology	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	No
CAT25256YI-GT3	onsemi	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	No
CAV25256YE-GT3	onsemi	10 MHz	2.5V ~ 5.5V	-40°C ~ 125°C	5ms	8-TSSOP	Yes (AEC-Q100)
M95256-DFDW6TP	STMicroelectronics	20 MHz	1.7V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	No
M95256-DRDW3TP/K	STMicroelectronics	20 MHz	1.8V ~ 5.5V	-40°C ~ 125°C	4ms	8-TSSOP	Yes (AEC-Q100)
M95256-DRDW8TP/K	STMicroelectronics	20 MHz	1.8V ~ 5.5V	-40°C ~ 105°C	4ms	8-TSSOP	Yes (AEC-Q100)
M95256-RDW6TP	STMicroelectronics	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	No

Engineering Selection Recommendations

For Standard Industrial Applications (-40°C to 85°C)

The 25AA256-E/ST provides direct substitution with extended temperature capability within the same manufacturer ecosystem. The AT25256B-XHL-B and CAT25256YI-GT3 offer 20 MHz clock frequency for applications requiring higher data throughput. The M95256-DFDW6TP and M95256-RDW6TP from STMicroelectronics provide equivalent performance with alternative sourcing.

For Extended Temperature Applications (-40°C to 125°C)

The 25AA256-E/ST and M95256-DRDW3TP/K support the full extended temperature range. The CAV25256YE-GT3 provides automotive-grade qualification with AEC-Q100 certification at 10 MHz operation.

For Automotive Applications (AEC-Q100 Qualified)

The CAV25256YE-GT3, M95256-DRDW3TP/K, and M95256-DRDW8TP/K are AEC-Q100 qualified. The M95256-DRDW8TP/K extends operation to -40°C to 105°C with 20 MHz performance and 4ms write cycle time. Note that CAV25256YE-GT3 has a minimum supply voltage of 2.5V, which may limit compatibility in 1.8V systems.

For High-Speed Applications (20 MHz)

The AT25256B-XHL-B, CAT25256YI-GT3, M95256-DFDW6TP, M95256-DRDW3TP/K, M95256-DRDW8TP/K, and M95256-RDW6TP all operate at 20 MHz. Selection depends on temperature range and automotive qualification requirements.

Frequently Asked Questions (FAQ)

Q: Can I use a 20 MHz part as a direct replacement for the 10 MHz 25AA256-I/ST?

A: Yes. The 20 MHz parts (AT25256B-XHL-B, CAT25256YI-GT3, M95256-DFDW6TP, M95256-DRDW3TP/K, M95256-DRDW8TP/K, M95256-RDW6TP) are backward compatible. Higher clock frequency does not prevent operation in 10 MHz applications. The SPI interface remains identical.

Q: What is the difference between the M95256 variants (DFDW6TP, DRDW3TP/K, DRDW8TP/K, RDW6TP)?

A: These variants differ in packaging format (Tape & Reel vs. Cut Tape), temperature range, automotive qualification, and write cycle time. DRDW3TP/K and DRDW8TP/K include AEC-Q100 qualification. DRDW8TP/K extends to -40°C to 105°C. DFDW6TP and RDW6TP are non-automotive grades.

Q: Is the CAV25256YE-GT3 compatible with 1.8V supply systems?

A: No. The CAV25256YE-GT3 requires a minimum supply voltage of 2.5V, whereas the 25AA256-I/ST operates from 1.8V. This part is suitable only for systems with 2.5V or higher supply voltage.

Q: Do all substitute parts maintain the same 8-TSSOP package footprint?

A: Yes. All listed substitute parts use the 8-TSSOP package with 0.173" width and 4.40mm dimensions, ensuring PCB layout compatibility.

Q: Which substitute part offers the best performance improvement?

A: The M95256-DRDW8TP/K provides the highest performance with 20 MHz clock frequency, 4ms write cycle time (faster than the 5ms of the main part), and extended temperature range to -40°C to 105°C with AEC-Q100 automotive qualification.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All listed substitute parts maintain ROHS3 compliance and unlimited moisture sensitivity level (MSL 1), matching the environmental compliance of the 25AA256-I/ST.

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