25AA640AX-I/ST EEPROM Memory IC Equivalent & Substitute Parts

Part Overview

The 25AA640AX-I/ST is a 64Kbit Serial Peripheral Interface (SPI) EEPROM memory IC manufactured by Microchip Technology in an 8-TSSOP surface mount package. This non-volatile memory device operates across a supply voltage range of 1.8V to 5.5V with a 10 MHz clock frequency and is compliant with ROHS3 standards. The part is currently in active production status with 957 units in stock. Equivalent and substitute parts are identified based on matching memory capacity, interface protocol, package type, and electrical operating parameters to ensure functional compatibility in circuit applications.

Key Parameters

Parameter	Value
Memory Size	64Kbit
Memory Organization	8K x 8
Memory Interface	SPI
Clock Frequency	10 MHz
Package / Case	8-TSSOP (0.173", 4.40mm Width)
Voltage - Supply	1.8V ~ 5.5V
Operating Temperature	-40°C ~ 85°C (TA)
Write Cycle Time	5ms
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitute parts for the 25AA640AX-I/ST are grouped based on the following critical parameters that determine functional compatibility:

Core Compatibility Criteria:

Memory capacity: 64Kbit (8K x 8 organization)
Interface protocol: SPI
Package type: 8-TSSOP surface mount
Pin count and pitch: 8-pin, 0.173" width

Acceptable Parameter Variations:

Clock frequency: 5 MHz to 20 MHz (all support minimum 10 MHz operation or higher)
Supply voltage range: Must encompass or overlap with 1.8V ~ 5.5V
Operating temperature: Must support minimum -40°C ~ 85°C range
Write cycle time: 4ms to 5ms (functionally equivalent)
Manufacturer: Microchip Technology, STMicroelectronics, onsemi, Renesas Electronics Corporation

Substitution Groups:

Group 1 (Direct Equivalents): Identical clock frequency (10 MHz) and parameters
Group 2 (Enhanced Performance): Higher clock frequency (16-20 MHz) with compatible voltage and temperature ranges
Group 3 (Automotive Grade): AEC-Q100 qualified parts with extended temperature or enhanced reliability
Group 4 (Lower Clock Speed): 5 MHz operation suitable for applications not requiring higher frequencies

Parameter Comparison

Manufacturer Part Number	Manufacturer	Memory Size	Clock Frequency	Voltage Supply	Operating Temperature	Write Cycle Time	Package	Inventory (Pcs)
25AA640AX-I/ST	Microchip Technology	64Kbit	10 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	957
25AA640A-I/ST	Microchip Technology	64Kbit	10 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	3300
AT25640B-XHL-B	Microchip Technology	64Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	2300
CAV25640YE-GT3	onsemi	64Kbit	10 MHz	2.5V ~ 5.5V	-40°C ~ 125°C	5ms	8-TSSOP	1180
M95640-DFDW6TP	STMicroelectronics	64Kbit	20 MHz	1.7V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	1140
M95640-DRDW3TP/K	STMicroelectronics	64Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 125°C	4ms	8-TSSOP	17589
M95640-DRDW8TP/K	STMicroelectronics	64Kbit	16 MHz	1.8V ~ 5.5V	-40°C ~ 105°C	4ms	8-TSSOP	16302
M95640-RDW6TP	STMicroelectronics	64Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	45400
R1EX25064ATA00I#S0	Renesas Electronics Corporation	64Kbit	5 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	2328

Engineering Selection Recommendations

Direct Replacement (Highest Compatibility): The 25AA640A-I/ST from Microchip Technology is the primary direct equivalent, offering identical electrical specifications and package configuration with higher inventory availability (3300 units).

Performance-Enhanced Alternatives: The AT25640B-XHL-B, M95640-DRDW3TP/K, M95640-DRDW8TP/K, and M95640-RDW6TP provide higher clock frequencies (16-20 MHz) while maintaining compatible voltage and temperature operating ranges. These parts support faster data transfer rates and are suitable for applications requiring improved performance margins.

Automotive-Grade Options: The CAV25640YE-GT3 (onsemi) and M95640-DRDW3TP/K (STMicroelectronics) carry AEC-Q100 qualification and extended operating temperature ranges (-40°C ~ 125°C), appropriate for automotive and industrial applications requiring enhanced reliability certification.

Lower-Speed Alternative: The R1EX25064ATA00I#S0 from Renesas Electronics operates at 5 MHz and is suitable for applications where lower clock frequencies are acceptable, offering cost optimization for non-performance-critical designs.

Inventory Considerations: M95640-RDW6TP (45400 units) and M95640-DRDW3TP/K (17589 units) offer the highest stock availability for immediate procurement needs.

Frequently Asked Questions (FAQ)

Q: Can I substitute the 25AA640AX-I/ST with a higher clock frequency part like the M95640-RDW6TP (20 MHz)?

A: Yes. The M95640-RDW6TP operates at 20 MHz, which is backward compatible with applications designed for 10 MHz operation. The higher clock frequency provides additional performance margin without affecting functional compatibility, provided the circuit design supports the faster data rate.

Q: What is the difference between the 25AA640A-I/ST and 25AA640AX-I/ST?

A: Both parts share identical electrical specifications (64Kbit, 10 MHz, 1.8V ~ 5.5V, 8-TSSOP package). The primary difference is the internal revision designation (A vs. AX). The 25AA640A-I/ST is the recommended equivalent with higher inventory availability.

Q: Are the automotive-grade parts (CAV25640YE-GT3 and M95640-DRDW3TP/K) suitable for non-automotive applications?

A: Yes. Automotive-grade parts meet or exceed standard industrial specifications and are fully compatible with general-purpose applications. The AEC-Q100 qualification indicates enhanced reliability testing and extended temperature range support, making them suitable for demanding industrial and consumer applications.

Q: Can I use the R1EX25064ATA00I#S0 (5 MHz) in place of the 25AA640AX-I/ST (10 MHz)?

A: The R1EX25064ATA00I#S0 is functionally compatible only if your application does not require clock frequencies above 5 MHz. If the circuit design specifies 10 MHz operation or higher, this part is not suitable. Verify clock frequency requirements in your application schematic before substitution.

Q: What are the packaging differences between these substitute parts?

A: All substitute parts use the 8-TSSOP (0.173", 4.40mm Width) surface mount package with identical pin configuration and pitch. Packaging variations exist only in supplier delivery format (Tube, Cut Tape & Digi-Reel, or Tape & Reel), which does not affect electrical or mechanical compatibility on the PCB.

Q: Which substitute part offers the best balance of performance, availability, and cost?

A: The M95640-RDW6TP provides optimal balance with 20 MHz clock frequency, 45400 units in stock, 1.8V ~ 5.5V supply compatibility, and 5ms write cycle time. For automotive applications, the M95640-DRDW3TP/K offers AEC-Q100 qualification with 17589 units available.

Q: Are all these parts ROHS3 compliant?

A: Yes. All listed substitute parts carry ROHS3 compliance certification, meeting environmental and hazardous substance restrictions for commercial and industrial applications.

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