25AA040XT-I/ST EEPROM Memory IC Equivalent & Substitute Parts

Part Overview

The 25AA040XT-I/ST is a 4Kbit Serial Peripheral Interface (SPI) EEPROM memory IC manufactured by Microchip Technology. This non-volatile memory device operates at 1 MHz clock frequency with a 512 x 8 memory organization, housed in an 8-TSSOP surface mount package. The part is currently in active production status with ROHS3 compliance and unlimited moisture sensitivity rating (MSL 1). Substitute parts are necessary when addressing supply constraints, packaging format requirements, or performance specifications that exceed the original device's clock frequency capabilities.

Key Parameters

Parameter	Value
Memory Size	4Kbit
Memory Organization	512 x 8
Memory Interface	SPI
Clock Frequency	1 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
MSL Rating	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility for the 25AA040XT-I/ST is determined by the following critical parameters:

Core Compatibility Requirements:

Memory Size: 4Kbit (fixed requirement)
Memory Organization: 512 x 8 (fixed requirement)
Memory Interface: SPI (fixed requirement)
Package Type: 8-TSSOP with 0.173" width and 4.40mm width (fixed requirement)
Voltage Supply Range: Must encompass or be compatible with 1.8V ~ 5.5V
Operating Temperature: Must support -40°C ~ 85°C minimum
RoHS Status: ROHS3 Compliant (regulatory requirement)

Performance Parameters (Flexible):

Clock Frequency: Original operates at 1 MHz; substitutes may operate at higher frequencies (5 MHz, 20 MHz) without functional impact
Write Cycle Time: Original specifies 5ms; substitutes with 4ms or 5ms are acceptable
MSL Rating: Original is MSL 1; substitutes with MSL 1 or MSL 3 are acceptable
Packaging Format: Original is Tape & Reel (TR); substitutes in Tube or Cut Tape formats are acceptable for different procurement scenarios

All substitute parts listed maintain identical memory capacity, organization, interface protocol, and physical package dimensions while offering equivalent or superior electrical performance characteristics.

Parameter Comparison

Part Number	Manufacturer	Memory Size	Clock Frequency	Voltage Supply	Operating Temp	Write Cycle Time	Package	Packaging Format	MSL
25AA040XT-I/ST	Microchip Technology	4Kbit	1 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tape & Reel	1
AT25040B-XHL-B	Microchip Technology	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tube	3
AT25040B-XHL-T	Microchip Technology	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tape & Reel	3
CAT25040YI-GT3	onsemi	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tape & Reel	1
M95040-DFDW6TP	STMicroelectronics	4Kbit	20 MHz	1.7V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tape & Reel	1
M95040-DRDW3TP/K	STMicroelectronics	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 125°C	4ms	8-TSSOP	Cut Tape & Digi-Reel	1
M95040-DRDW8TP/K	STMicroelectronics	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 105°C	4ms	8-TSSOP	Tape & Reel	1
M95040-RDW6TP	STMicroelectronics	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Cut Tape & Digi-Reel	1
M95040-WDW6TP	STMicroelectronics	4Kbit	20 MHz	2.5V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tape & Reel	1
R1EX25004ATA00I#S0	Renesas Electronics Corporation	4Kbit	5 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tape & Reel	1

Engineering Selection Recommendations

Direct Substitutes (Identical Specifications): CAT25040YI-GT3 from onsemi provides identical electrical and thermal specifications to the 25AA040XT-I/ST with the same 1 MHz minimum clock frequency capability, MSL 1 rating, and operating temperature range. Both parts maintain ROHS3 compliance and are available in Tape & Reel packaging.

Higher Performance Substitutes (Enhanced Clock Frequency): AT25040B-XHL-T, M95040-DFDW6TP, M95040-DRDW8TP/K, M95040-RDW6TP, and M95040-WDW6TP operate at 20 MHz clock frequency, providing superior performance headroom while maintaining backward compatibility with 1 MHz SPI bus implementations. These parts are suitable for applications requiring higher data throughput or future performance scaling.

Automotive-Grade Substitutes: M95040-DRDW3TP/K and M95040-DRDW8TP/K carry AEC-Q100 automotive qualification with extended operating temperature ranges (-40°C to 125°C and -40°C to 105°C respectively) and reduced write cycle times (4ms). These parts are appropriate for automotive and industrial applications requiring enhanced reliability certifications.

Lower Clock Frequency Alternative: R1EX25004ATA00I#S0 from Renesas operates at 5 MHz, providing intermediate performance between the original 1 MHz specification and higher-frequency alternatives while maintaining full electrical compatibility.

Packaging Format Alternatives: AT25040B-XHL-B is available in Tube packaging for applications requiring alternative procurement and handling formats. M95040-DRDW3TP/K and M95040-RDW6TP are available in Cut Tape & Digi-Reel format for specific assembly line requirements.

Voltage Supply Consideration: M95040-WDW6TP operates with a minimum supply voltage of 2.5V, making it unsuitable for applications requiring 1.8V operation. All other substitutes maintain the full 1.8V ~ 5.5V supply range of the original part.

Frequently Asked Questions (FAQ)

Q: Can I use a 20 MHz substitute part in a circuit designed for the 1 MHz 25AA040XT-I/ST?

A: Yes. The substitute parts operating at 20 MHz are backward compatible with 1 MHz SPI bus implementations. The SPI interface operates at the clock frequency determined by the host controller, not the memory device. A 20 MHz-rated EEPROM functions correctly on a 1 MHz bus.

Q: What is the difference between Tape & Reel, Tube, and Cut Tape packaging formats?

A: Packaging format affects procurement and assembly handling only. Tape & Reel (TR) is standard for high-volume automated assembly. Tube packaging is used for lower-volume orders and manual handling. Cut Tape & Digi-Reel combines cut tape with reel management for specific assembly processes. All formats contain identical electronic components in the same 8-TSSOP package.

Q: Are MSL 1 and MSL 3 rated parts interchangeable?

A: MSL (Moisture Sensitivity Level) ratings indicate moisture absorption characteristics during storage. MSL 1 parts have unlimited shelf life without baking. MSL 3 parts require baking after 168 hours of exposure to ambient humidity. Both are functionally equivalent once soldered. Selection depends on storage and handling procedures in your manufacturing environment.

Q: Why do some substitutes have faster write cycle times (4ms vs 5ms)?

A: Write cycle time improvements reflect manufacturing process enhancements. A 4ms write cycle is superior to 5ms and does not create compatibility issues. Applications designed for 5ms write cycles operate correctly with faster devices.

Q: Is the M95040-WDW6TP suitable as a direct replacement?

A: M95040-WDW6TP is not suitable if your application requires operation below 2.5V supply voltage. The original 25AA040XT-I/ST and most substitutes support 1.8V minimum. Verify your circuit's minimum supply voltage before selecting this part.

Q: What does AEC-Q100 qualification mean?

A: AEC-Q100 is an automotive industry reliability qualification standard. M95040-DRDW3TP/K and M95040-DRDW8TP/K carry this certification, indicating enhanced testing and reliability assurance for automotive applications. These parts are appropriate for automotive and high-reliability industrial applications.

Q: Can I substitute based on clock frequency alone?

A: No. Clock frequency is only one parameter. All substitutes must maintain identical memory size (4Kbit), organization (512 x 8), interface (SPI), package type (8-TSSOP), and voltage supply range compatibility. Verify all parameters before selection.

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