Equivalent & Substitute Parts for 25AA040XT/ST

Part Overview

The Microchip Technology 25AA040XT/ST is a 4Kbit EEPROM memory IC with SPI interface operating at 1 MHz, housed in an 8-TSSOP package. This part is classified as obsolete, which necessitates identification of active equivalent and substitute components for new designs and ongoing production requirements. The 25AA040XT/ST provides non-volatile memory storage with a supply voltage range of 1.8V to 5.5V and operates across the industrial temperature range of 0°C to 70°C.

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	0°C ~ 70°C
Package Type	8-TSSOP (0.173", 4.40mm Width)
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution for the 25AA040XT/ST is determined by the following critical parameters: 4Kbit memory capacity, 512 x 8 organization, SPI interface, 8-TSSOP package, and voltage supply compatibility (1.8V ~ 5.5V minimum). Clock frequency represents a secondary consideration; parts operating at higher frequencies (10 MHz, 20 MHz) are forward-compatible with 1 MHz applications. Operating temperature range and product status (active vs. obsolete) are additional factors for design continuity.

Substitute parts are grouped into three categories:

Category 1: Microchip 25AA040 Series (Active Status) Parts with identical base specifications and active product status: 25AA040AT-I/ST, 25AA040AXT-I/ST, and 25AA040XT-I/ST. These maintain full electrical and mechanical compatibility.

Category 2: Microchip 25LC040 Series (Extended Voltage Range) The 25LC040A-I/ST operates with a minimum supply voltage of 2.5V (vs. 1.8V for 25AA040XT/ST) and offers extended temperature range (-40°C to 85°C).

Category 3: Cross-Manufacturer Alternatives Parts from onsemi (CAT25040YI-GT3, CAV25040YE-GT3) and STMicroelectronics (M95040-DFDW6TP, M95040-DRDW3TP/K) provide equivalent 4Kbit SPI EEPROM functionality in 8-TSSOP packaging with active product status.

Parameter Comparison

Part Number	Manufacturer	Memory Size	Clock Frequency	Voltage Supply	Operating Temperature	Product Status	Package
25AA040XT/ST	Microchip	4Kbit	1 MHz	1.8V ~ 5.5V	0°C ~ 70°C	Obsolete	8-TSSOP
25AA040AT-I/ST	Microchip	4Kbit	10 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	Active	8-TSSOP
25AA040AXT-I/ST	Microchip	4Kbit	10 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	Active	8-TSSOP
25AA040XT-I/ST	Microchip	4Kbit	1 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	Active	8-TSSOP
25LC040A-I/ST	Microchip	4Kbit	10 MHz	2.5V ~ 5.5V	-40°C ~ 85°C	Active	8-TSSOP
AT25040B-XHL-B	Microchip	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	Active	8-TSSOP
AT25040B-XHL-T	Microchip	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	Active	8-TSSOP
CAT25040YI-GT3	onsemi	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	Active	8-TSSOP
CAV25040YE-GT3	onsemi	4Kbit	10 MHz	2.5V ~ 5.5V	-40°C ~ 125°C	Active	8-TSSOP
M95040-DFDW6TP	STMicroelectronics	4Kbit	20 MHz	1.7V ~ 5.5V	-40°C ~ 85°C	Active	8-TSSOP
M95040-DRDW3TP/K	STMicroelectronics	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 125°C	Active	8-TSSOP

Engineering Selection Recommendations

For direct replacement of the obsolete 25AA040XT/ST in existing designs, the 25AA040XT-I/ST offers identical clock frequency (1 MHz) with extended operating temperature range (-40°C to 85°C) and active product status. This part maintains full backward compatibility while ensuring long-term supply availability.

For new designs requiring enhanced performance, the 25AA040AT-I/ST or 25AA040AXT-I/ST provide 10 MHz operation with identical voltage supply range and active status. The AT25040B-XHL-T variant offers 20 MHz operation with high inventory availability (18,647 pcs) and ROHS3 compliance.

Cross-manufacturer alternatives include the onsemi CAT25040YI-GT3 (20 MHz, 60,300 pcs in stock) and STMicroelectronics M95040-DRDW3TP/K (20 MHz, automotive-qualified with AEC-Q100 certification and -40°C to 125°C operating range). The M95040-DRDW3TP/K is suitable for applications requiring extended temperature performance and automotive-grade reliability.

For applications with minimum supply voltage constraints above 2.5V, the 25LC040A-I/ST and CAV25040YE-GT3 are acceptable alternatives. The CAV25040YE-GT3 provides automotive qualification and extended temperature range to 125°C.

Frequently Asked Questions (FAQ)

Q: Can the 25AA040XT/ST be replaced with a higher clock frequency part such as the AT25040B-XHL-T (20 MHz)?

A: Yes. The 25AA040XT/ST operates at 1 MHz maximum clock frequency. Parts rated for 10 MHz or 20 MHz are forward-compatible and will operate correctly in applications designed for 1 MHz operation. The higher frequency rating indicates the part's maximum capability, not a requirement for operation.

Q: What is the difference between 25AA040AT-I/ST and 25AA040AXT-I/ST?

A: Both parts are Microchip 25AA040 series with 10 MHz clock frequency, 4Kbit capacity, and 8-TSSOP packaging. The primary difference is packaging format: 25AA040AT-I/ST is supplied in tube packaging, while 25AA040AXT-I/ST is supplied in tape and reel (TR) format. Electrical specifications are identical.

Q: Is the 25LC040A-I/ST a suitable substitute for the 25AA040XT/ST?

A: The 25LC040A-I/ST is electrically compatible but has a higher minimum supply voltage (2.5V vs. 1.8V). It is suitable only if the application's power supply operates at 2.5V or higher. Both parts share identical 4Kbit capacity, SPI interface, 8-TSSOP package, and 5ms write cycle time.

Q: Why do some substitute parts have lower minimum supply voltages (1.7V for M95040-DFDW6TP)?

A: Lower minimum supply voltage specifications indicate the part's ability to operate at reduced power levels. Parts with 1.7V or 1.8V minimums are compatible with applications designed for 1.8V to 5.5V operation. The 25AA040XT/ST's 1.8V minimum is within the operating range of these alternatives.

Q: Are automotive-qualified parts (CAV25040YE-GT3, M95040-DRDW3TP/K) necessary for non-automotive applications?

A: Automotive qualification (AEC-Q100) is not required for non-automotive applications. These parts are suitable for general industrial and commercial use and offer extended temperature range (-40°C to 125°C) as an additional benefit. Selection should be based on application temperature requirements and supply availability.

Q: What is the significance of MSL (Moisture Sensitivity Level) ratings?

A: MSL 1 (Unlimited) indicates the part has no moisture sensitivity restrictions and requires no special handling or storage conditions. MSL 3 (168 Hours) requires controlled storage and handling to prevent moisture absorption. For applications with standard manufacturing environments, MSL 1 parts are preferred for simplified logistics.

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