Equivalent & Substitute Parts for 25C040XT/ST

Part Overview

The 25C040XT/ST is a 4Kbit EEPROM memory IC manufactured by Microchip Technology, featuring SPI interface operation at 3 MHz with 8-TSSOP surface mount packaging. This part is classified as obsolete, making substitute components necessary for new designs and ongoing production requirements. The device operates within a 4.5V to 5.5V supply range and supports standard EEPROM read/write operations with a 5ms write cycle time.

Key Parameters

Parameter	Value
Memory Size	4Kbit
Memory Organization	512 x 8
Memory Interface	SPI
Clock Frequency	3 MHz
Voltage Supply Range	4.5V ~ 5.5V
Operating Temperature	0°C ~ 70°C
Write Cycle Time	5ms
Package Type	8-TSSOP (0.173", 4.40mm Width)
Product Status	Obsolete
RoHS Compliance	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the 25C040XT/ST is determined by the following critical parameters: 4Kbit memory capacity, 512 x 8 organization, SPI interface, 8-TSSOP package, and functional compatibility within specified electrical operating conditions. Substitute parts are grouped into two categories based on operational characteristics:

Category 1: Direct Functional Equivalents — Parts maintaining the 3 MHz clock frequency specification with compatible voltage and temperature ranges. These provide drop-in replacement capability with minimal design modification.

Category 2: Enhanced Performance Alternatives — Parts with higher clock frequencies (10 MHz) or extended voltage ranges (1.8V minimum) that maintain backward compatibility while offering improved performance margins or broader application flexibility.

All substitute parts listed maintain ROHS3 compliance, identical package geometry, and equivalent memory organization. Selection between categories depends on system timing requirements and supply voltage constraints.

Parameter Comparison

Part Number	Manufacturer	Memory Size	Clock Frequency	Voltage Supply	Operating Temperature	Package	Product Status
25C040XT/ST	Microchip Technology	4Kbit	3 MHz	4.5V ~ 5.5V	0°C ~ 70°C	8-TSSOP	Obsolete
25C040XT-I/ST	Microchip Technology	4Kbit	3 MHz	4.5V ~ 5.5V	-40°C ~ 85°C	8-TSSOP	Active
25AA040AT-I/ST	Microchip Technology	4Kbit	10 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	8-TSSOP	Active
25AA040AXT-I/ST	Microchip Technology	4Kbit	10 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	8-TSSOP	Active
25AA040XT-I/ST	Microchip Technology	4Kbit	1 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	8-TSSOP	Active
25LC040AT-E/ST	Microchip Technology	4Kbit	10 MHz	2.5V ~ 5.5V	-40°C ~ 125°C	8-TSSOP	Active
25LC040AT-I/ST	Microchip Technology	4Kbit	10 MHz	2.5V ~ 5.5V	-40°C ~ 85°C	8-TSSOP	Active
25LC040AXT-E/ST	Microchip Technology	4Kbit	10 MHz	2.5V ~ 5.5V	-40°C ~ 125°C	8-TSSOP	Active
25LC040AXT-I/ST	Microchip Technology	4Kbit	10 MHz	2.5V ~ 5.5V	-40°C ~ 85°C	8-TSSOP	Active
25LC040XT-I/ST	Microchip Technology	4Kbit	2 MHz	2.5V ~ 5.5V	-40°C ~ 85°C	8-TSSOP	Active
25LC040XT/ST	Microchip Technology	4Kbit	2 MHz	2.5V ~ 5.5V	0°C ~ 70°C	8-TSSOP	Active

Engineering Selection Recommendations

Primary Substitute: 25C040XT-I/ST — This part maintains identical electrical specifications (4.5V ~ 5.5V, 3 MHz operation) while offering active product status and extended temperature range (-40°C ~ 85°C). It provides direct functional equivalence with improved availability and lifecycle support.

Extended Temperature Applications: 25LC040AT-E/ST or 25LC040AXT-E/ST — These parts support operation to 125°C and maintain 10 MHz clock frequency with 2.5V minimum supply voltage. Selection is appropriate for applications requiring enhanced thermal performance while accepting lower minimum voltage specification.

Low Voltage Applications: 25AA040AT-I/ST or 25AA040AXT-I/ST — These parts operate from 1.8V minimum supply, enabling use in low-power or battery-powered systems. The 10 MHz clock frequency provides performance margin over the original 3 MHz specification.

Backward Compatible Alternative: 25LC040XT/ST — This part matches the original 0°C ~ 70°C temperature range and 2.5V ~ 5.5V supply specification, with 2 MHz clock frequency operation. It is suitable for direct replacement in existing designs with identical thermal constraints.

All recommended substitutes maintain ROHS3 compliance, identical 8-TSSOP package geometry, and 4Kbit memory capacity with 512 x 8 organization.

Frequently Asked Questions (FAQ)

Q: Can 25C040XT-I/ST directly replace 25C040XT/ST in existing designs?

A: Yes. The 25C040XT-I/ST maintains identical memory capacity (4Kbit), interface type (SPI), clock frequency (3 MHz), and package (8-TSSOP). The supply voltage range (4.5V ~ 5.5V) is identical. The extended operating temperature range (-40°C ~ 85°C versus 0°C ~ 70°C) provides additional margin without affecting compatibility.

Q: What is the difference between 25AA040 and 25LC040 series parts?

A: The 25AA040 series operates from 1.8V minimum supply voltage, while 25LC040 series operates from 2.5V minimum. Both maintain 4Kbit capacity and SPI interface. Selection depends on system supply voltage requirements. The 25AA040 series is suitable for low-voltage applications; the 25LC040 series is appropriate for standard 2.5V or higher supply systems.

Q: Are higher clock frequency substitutes (10 MHz) compatible with designs specified for 3 MHz operation?

A: Yes. Parts operating at 10 MHz (25AA040AT-I/ST, 25LC040AT-I/ST, 25LC040AXT-I/ST) are backward compatible with 3 MHz designs. The higher clock frequency provides performance margin and does not require design modification. System timing constraints must accommodate the faster operation, but this typically presents no compatibility issues.

Q: What packaging considerations apply to these substitutes?

A: All listed substitute parts use 8-TSSOP surface mount packaging with identical dimensions (0.173" width, 4.40mm). Pin configuration and footprint are identical across all parts, enabling direct PCB-level substitution without layout modification.

Q: Which substitute is recommended for new designs?

A: The 25C040XT-I/ST is recommended for new designs requiring 3 MHz operation and 4.5V ~ 5.5V supply range. For applications without strict frequency constraints, the 25LC040XT-I/ST (2 MHz) or 25AA040AT-I/ST (10 MHz) offer active product status with extended temperature or voltage flexibility.

Q: Are all substitutes ROHS3 compliant?

A: Yes. All listed substitute parts maintain ROHS3 compliance, matching the original 25C040XT/ST specification.

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