25LC040X/ST EEPROM Memory IC Equivalent & Substitute Parts

Part Overview

The 25LC040X/ST is a 4Kbit Serial Peripheral Interface (SPI) EEPROM memory IC manufactured by Microchip Technology, packaged in 8-TSSOP surface mount configuration. This non-volatile memory device operates at 2 MHz clock frequency with a supply voltage range of 2.5V to 5.5V and is rated for 0°C to 70°C operating temperature. The part is currently active in production status and ROHS3 compliant.

Substitute parts are necessary when the original 25LC040X/ST becomes unavailable, when extended temperature range operation is required, when higher clock frequency performance is needed, or when alternative packaging formats are preferred for manufacturing optimization.

Key Parameters

Parameter	25LC040X/ST
Memory Size	4Kbit
Memory Organization	512 x 8
Memory Interface	SPI
Clock Frequency	2 MHz
Write Cycle Time	5ms
Voltage Supply Range	2.5V ~ 5.5V
Operating Temperature	0°C ~ 70°C
Package / Case	8-TSSOP (0.173", 4.40mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility for the 25LC040X/ST is determined by the following critical parameters:

Mandatory Compatibility Parameters:

Memory Size: 4Kbit (all substitutes must match)
Memory Organization: 512 x 8 (all substitutes must match)
Memory Interface: SPI (all substitutes must match)
Package / Case: 8-TSSOP (all substitutes must match)
Mounting Type: Surface Mount (all substitutes must match)

Allowable Variation Parameters:

Clock Frequency: May be equal to or greater than 2 MHz
Write Cycle Time: May be equal to or less than 5ms
Voltage Supply Range: Must encompass or exceed 2.5V ~ 5.5V minimum requirement
Operating Temperature: May be extended beyond 0°C ~ 70°C
Manufacturer: Alternative manufacturers acceptable if all mandatory parameters match

All identified substitute parts meet the mandatory compatibility requirements. Variations in clock frequency, temperature range, and voltage specifications represent performance enhancements or extended operational capabilities suitable for direct substitution in applications designed for the 25LC040X/ST.

Parameter Comparison

Part Number	Manufacturer	Memory Size	Clock Frequency	Voltage Supply	Operating Temperature	Write Cycle Time	Package	Packaging Format
25LC040X/ST	Microchip Technology	4Kbit	2 MHz	2.5V ~ 5.5V	0°C ~ 70°C	5ms	8-TSSOP	Tube
25LC040A-I/ST	Microchip Technology	4Kbit	10 MHz	2.5V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tube
25LC040AX-I/ST	Microchip Technology	4Kbit	10 MHz	2.5V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tube
AT25040B-XHL-B	Microchip Technology	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tube
M95040-DFDW6TP	STMicroelectronics	4Kbit	20 MHz	1.7V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tape & Reel
M95040-DRDW3TP/K	STMicroelectronics	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 125°C	4ms	8-TSSOP	Cut Tape & Digi-Reel
M95040-DRDW8TP/K	STMicroelectronics	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 105°C	4ms	8-TSSOP	Tape & Reel
M95040-RDW6TP	STMicroelectronics	4Kbit	20 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Cut Tape & Digi-Reel
M95040-WDW6TP	STMicroelectronics	4Kbit	20 MHz	2.5V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tape & Reel
R1EX25004ATA00I#S0	Renesas Electronics Corporation	4Kbit	5 MHz	1.8V ~ 5.5V	-40°C ~ 85°C	5ms	8-TSSOP	Tape & Reel

Engineering Selection Recommendations

Direct Substitution (Microchip Technology): The 25LC040A-I/ST and 25LC040AX-I/ST from Microchip Technology provide direct substitution with enhanced performance. Both parts maintain identical supply voltage compatibility (2.5V ~ 5.5V) and package specifications while offering 10 MHz clock frequency and extended operating temperature range (-40°C ~ 85°C). These parts are verified as programmable and carry ROHS3 compliance.

Enhanced Performance Substitutes (STMicroelectronics): The M95040 series from STMicroelectronics (M95040-DFDW6TP, M95040-DRDW3TP/K, M95040-DRDW8TP/K, M95040-RDW6TP, M95040-WDW6TP) all provide 20 MHz clock frequency operation with extended temperature ranges. The M95040-DRDW3TP/K and M95040-DRDW8TP/K variants include AEC-Q100 automotive qualification and support operating temperatures up to 125°C and 105°C respectively. These parts are ROHS3 compliant and available in multiple packaging formats.

Alternative Manufacturer Substitute (Renesas Electronics Corporation): The R1EX25004ATA00I#S0 from Renesas Electronics Corporation provides 5 MHz clock frequency operation with extended temperature range (-40°C ~ 85°C) and lower minimum supply voltage (1.8V). This part is ROHS3 compliant and available in Tape & Reel packaging format.

Voltage Supply Consideration: The 25LC040X/ST requires minimum 2.5V supply voltage. Substitutes with lower minimum voltage specifications (1.7V, 1.8V) are fully compatible and provide additional design flexibility for lower-voltage applications.

Frequently Asked Questions (FAQ)

Q: Can I use a substitute part with higher clock frequency than the original 25LC040X/ST? A: Yes. The 25LC040X/ST operates at 2 MHz. Substitute parts with 5 MHz, 10 MHz, or 20 MHz clock frequencies are fully compatible and provide backward compatibility. Higher clock frequency capability does not affect operation in circuits designed for 2 MHz operation.

Q: Are all substitute parts available in the same 8-TSSOP package? A: Yes. All identified substitute parts use the 8-TSSOP (0.173", 4.40mm Width) package. However, packaging formats differ: some are supplied in Tube, others in Tape & Reel, or Cut Tape & Digi-Reel formats. Verify packaging format compatibility with your procurement and assembly requirements.

Q: What is the difference between Microchip Technology and STMicroelectronics substitutes? A: Both manufacturers provide ROHS3 compliant 4Kbit SPI EEPROM devices in 8-TSSOP packages. Microchip Technology substitutes (25LC040A-I/ST, 25LC040AX-I/ST) maintain the original supply voltage range (2.5V ~ 5.5V). STMicroelectronics substitutes offer lower minimum supply voltage (1.7V ~ 1.8V) and some variants include automotive-grade qualification (AEC-Q100).

Q: Can I substitute the 25LC040X/ST with a part rated for -40°C ~ 125°C when my application only requires 0°C ~ 70°C? A: Yes. Extended temperature range capability is a performance enhancement. A part rated for -40°C ~ 125°C will operate correctly in applications requiring only 0°C ~ 70°C operation. This substitution provides additional design margin and potential future application flexibility.

Q: What does AEC-Q100 qualification mean? A: AEC-Q100 is an automotive industry qualification standard. Parts carrying this qualification (M95040-DRDW3TP/K, M95040-DRDW8TP/K) meet automotive-grade reliability and testing requirements. These parts are suitable for both automotive and general industrial applications.

Q: Are all substitute parts ROHS3 compliant? A: Yes. All identified substitute parts carry ROHS3 compliance status, matching the original 25LC040X/ST specification.

Q: What is the significance of write cycle time differences (4ms vs 5ms)? A: Write cycle time of 4ms is faster than 5ms. Substitutes with 4ms write cycle time (M95040-DRDW3TP/K, M95040-DRDW8TP/K) provide improved write performance. This is a performance enhancement and does not affect compatibility with circuits designed for 5ms write cycle time.

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