24FC128T-I/ST EEPROM Memory IC Equivalent & Substitute Parts

Part Overview

The 24FC128T-I/ST is a 128Kbit I2C EEPROM memory IC manufactured by Microchip Technology in 8-TSSOP surface mount packaging. This non-volatile memory device operates across a wide voltage range (1.7V to 5.5V) and temperature range (-40°C to 85°C), making it suitable for embedded systems, data logging, and configuration storage applications. The part is currently in active production status with ROHS3 compliance and unlimited moisture sensitivity rating (MSL 1).

Equivalent and substitute parts are necessary when the primary part experiences supply constraints, inventory limitations, or when design flexibility allows for alternative manufacturers while maintaining functional compatibility.

Key Parameters

Parameter	Value
Memory Size	128Kbit
Memory Organization	16K x 8
Memory Interface	I2C
Clock Frequency	1 MHz
Access Time	400 ns
Write Cycle Time	5ms
Voltage Supply Range	1.7V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package Type	8-TSSOP
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility for the 24FC128T-I/ST is determined by the following critical parameters:

Primary Substitution Criteria:

Memory capacity: 128Kbit (fixed requirement)
Memory organization: 16K x 8 (fixed requirement)
Interface protocol: I2C (fixed requirement)
Package type: 8-TSSOP (fixed requirement)
Operating temperature range: -40°C ~ 85°C (fixed requirement)
Write cycle time: 5ms (fixed requirement)

Secondary Compatibility Parameters:

Clock frequency: 1 MHz (primary specification) or 400 kHz (reduced speed, backward compatible)
Access time: 400 ns (primary) to 900 ns (acceptable variance)
Voltage supply range: Minimum 1.7V required; upper limit 5.5V or higher acceptable
Moisture sensitivity: MSL 1 or MSL 3 acceptable for most applications

Substitute parts are grouped into two categories: direct equivalents matching all primary parameters, and functional alternatives with reduced clock frequency or slightly extended access times that remain compatible with I2C protocol specifications.

Parameter Comparison

Part Number	Manufacturer	Memory Size	Clock Frequency	Access Time	Voltage Supply	Package	Product Status	MSL Rating
24FC128T-I/ST	Microchip Technology	128Kbit	1 MHz	400 ns	1.7V ~ 5.5V	8-TSSOP	Active	1
24FC128-I/ST	Microchip Technology	128Kbit	1 MHz	400 ns	1.7V ~ 5.5V	8-TSSOP	Active	1
24AA128T-I/ST	Microchip Technology	128Kbit	400 kHz	900 ns	1.7V ~ 5.5V	8-TSSOP	Active	1
AT24C128C-XHM-T	Microchip Technology	128Kbit	1 MHz	550 ns	1.7V ~ 5.5V	8-TSSOP	Active	3
BR24G128FVT-3AGE2	Rohm Semiconductor	128Kbit	1 MHz	Not specified	1.7V ~ 5.5V	8-TSSOP-B	Active	1
BR24G128FVT-3GE2	Rohm Semiconductor	128Kbit	400 kHz	Not specified	1.6V ~ 5.5V	8-TSSOP-B	Active	1
BR24S128FVT-WE2	Rohm Semiconductor	128Kbit	400 kHz	Not specified	1.7V ~ 5.5V	8-TSSOP-B	Active	1
CAT24C128YI-GT3	onsemi	128Kbit	1 MHz	400 ns	1.8V ~ 5.5V	8-TSSOP	Active	1
M24128-BRDW6TP	STMicroelectronics	128Kbit	1 MHz	450 ns	1.8V ~ 5.5V	8-TSSOP	Active	1
M24128-BWDW6TP	STMicroelectronics	128Kbit	1 MHz	450 ns	2.5V ~ 5.5V	8-TSSOP	Not For New Designs	1
M24128-DFDW6TP	STMicroelectronics	128Kbit	1 MHz	450 ns	1.7V ~ 5.5V	8-TSSOP	Active	1

Engineering Selection Recommendations

Tier 1 - Direct Equivalents (Recommended for New Designs):

24FC128-I/ST (Microchip Technology) is the closest direct equivalent, differing only in packaging format (Tube vs. standard). Both parts share identical electrical specifications and active product status.

24AA128T-I/ST (Microchip Technology) provides functional compatibility with reduced clock frequency (400 kHz vs. 1 MHz) and extended access time (900 ns vs. 400 ns). This part is verified for DiGi-Electronics programmability and maintains active status.

CAT24C128YI-GT3 (onsemi) matches the primary electrical specifications with 1 MHz operation and 400 ns access time. Minimum voltage supply is 1.8V (vs. 1.7V for the primary part). Active product status and ROHS3 compliance confirmed.

M24128-DFDW6TP (STMicroelectronics) operates at 1 MHz with 450 ns access time and 1.7V minimum voltage supply. Active product status with ROHS3 compliance.

Tier 2 - Functional Alternatives (Acceptable for Speed-Tolerant Applications):

BR24G128FVT-3AGE2 and BR24S128FVT-WE2 (Rohm Semiconductor) provide 128Kbit I2C EEPROM functionality in 8-TSSOP-B packaging. BR24S128FVT-WE2 is verified for DiGi-Electronics programmability. Both operate at 400 kHz with active product status.

Not Recommended for New Designs:

M24128-BWDW6TP (STMicroelectronics) carries "Not For New Designs" status and has a minimum voltage supply of 2.5V, which may not be compatible with 1.7V supply applications.

Frequently Asked Questions (FAQ)

Q: Can I substitute 24AA128T-I/ST for 24FC128T-I/ST in my design?

A: Yes, with operational considerations. The 24AA128T-I/ST operates at 400 kHz clock frequency versus 1 MHz for the primary part, resulting in extended access time (900 ns vs. 400 ns). This substitution is valid for applications where reduced I2C bus speed is acceptable. Both parts maintain identical 128Kbit capacity, 16K x 8 organization, and 5ms write cycle time.

Q: What is the difference between 8-TSSOP and 8-TSSOP-B packaging?

A: Both package types are 8-pin thin shrink small outline packages with 0.173" width and 4.40mm body width. The "-B" designation indicates a variant used by Rohm Semiconductor. Pin compatibility and PCB footprint are equivalent for standard I2C EEPROM applications.

Q: Are there voltage supply compatibility issues between substitute parts?

A: The primary part 24FC128T-I/ST operates from 1.7V to 5.5V. Most substitutes maintain this range. CAT24C128YI-GT3 and M24128-BRDW6TP have a minimum of 1.8V, and M24128-BWDW6TP requires 2.5V minimum. Verify your application's minimum supply voltage before selection.

Q: Which substitute parts are verified for programmability?

A: 24AA128T-I/ST, M24128-BRDW6TP, M24128-BWDW6TP, and BR24S128FVT-WE2 are verified for DiGi-Electronics programmability. The primary part 24FC128T-I/ST is not verified.

Q: Can I use parts with MSL 3 rating instead of MSL 1?

A: AT24C128C-XHM-T carries MSL 3 (168 hours) versus MSL 1 (unlimited) for the primary part. MSL 3 requires controlled moisture exposure during storage and handling. Use MSL 3 parts only if your manufacturing process includes appropriate moisture control measures.

Q: What is the inventory status for these substitute parts?

A: Inventory levels vary. 24AA128T-I/ST has the highest availability (88,298 pcs), while BR24G128FVT-3GE2 has the lowest (3,010 pcs). Verify current stock with your supplier before design commitment.

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