FT24C128A-USR-T EEPROM 128Kbit I2C Memory IC Equivalent & Substitute Parts

Part Overview

The FT24C128A-USR-T is a 128Kbit EEPROM memory IC with I2C interface manufactured by Fremont Micro Devices Ltd. This device is discontinued at DiGi Electronics, necessitating identification of equivalent and substitute parts for ongoing design requirements and production needs. The part operates across a wide supply voltage range (1.8V to 5.5V) and temperature range (-40°C to 85°C), making it suitable for industrial and consumer applications requiring non-volatile serial memory storage.

Key Parameters

Parameter	Value
Memory Type	Non-Volatile EEPROM
Memory Size	128Kbit
Memory Organization	16K x 8
Memory Interface	I2C
Clock Frequency	1 MHz
Access Time	550 ns
Write Cycle Time	5 ms
Voltage Supply Range	1.8V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package Type	8-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant
MSL Rating	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the FT24C128A-USR-T is determined by strict equivalence across the following critical parameters:

Primary Equivalence Criteria:

Memory capacity: 128Kbit
Memory organization: 16K x 8
Interface protocol: I2C
Package type: 8-SOIC or 8-SOP with compatible pin pitch (0.154" width)
Supply voltage range: Minimum 1.8V, maximum 5.5V
Operating temperature range: -40°C to 85°C
Write cycle time: 5 ms
RoHS3 compliance

Secondary Compatibility Factors:

Clock frequency: 1 MHz operation (preferred) or 400 kHz (acceptable with performance trade-off)
Access time: 550 ns (preferred) or faster
Moisture sensitivity level: 1 (preferred) or 3 (acceptable)
Product status: Active preferred; discontinued acceptable if specifications match

Substitutes are grouped into two categories: parametric equivalents (identical specifications, different packaging or product status) and similar parts (compatible electrical specifications with minor parameter variations).

Parameter Comparison

Part Number	Manufacturer	Memory Size	Clock Frequency	Access Time	Voltage Supply	Package	Product Status	MSL
FT24C128A-USR-T	Fremont Micro Devices	128Kbit	1 MHz	550 ns	1.8V ~ 5.5V	8-SOP	Discontinued	1
FT24C128A-ESG-T	Fremont Micro Devices	128Kbit	1 MHz	550 ns	1.8V ~ 5.5V	8-SOP	Active	1
FT24C128A-ESR-T	Fremont Micro Devices	128Kbit	1 MHz	550 ns	1.8V ~ 5.5V	8-SOP	Active	1
24AA128T-I/SN	Microchip Technology	128Kbit	400 kHz	900 ns	1.7V ~ 5.5V	8-SOIC	Active	3
24FC128-I/SN	Microchip Technology	128Kbit	1 MHz	400 ns	1.7V ~ 5.5V	8-SOIC	Active	1
24FC128T-I/SN	Microchip Technology	128Kbit	1 MHz	400 ns	1.7V ~ 5.5V	8-SOIC	Active	1
602-20012	Parallax Inc.	128Kbit	1 MHz	400 ns	1.7V ~ 5.5V	8-SOIC	Active	1
AT24C128C-SSHM-T	Microchip Technology	128Kbit	1 MHz	550 ns	1.7V ~ 5.5V	8-SOIC	Active	3
BR24G128F-3AGTE2	Rohm Semiconductor	128Kbit	1 MHz	Not specified	1.7V ~ 5.5V	8-SOP	Active	1
BR24G128F-3GTE2	Rohm Semiconductor	128Kbit	400 kHz	Not specified	1.6V ~ 5.5V	8-SOP	Active	1
BR24G128FJ-3AGTE2	Rohm Semiconductor	128Kbit	1 MHz	Not specified	1.7V ~ 5.5V	8-SOP-J	Active	1

Engineering Selection Recommendations

Direct Replacements (Parametric Equivalents):

FT24C128A-ESG-T and FT24C128A-ESR-T are parametric equivalents of the FT24C128A-USR-T with identical electrical specifications and packaging. Both are active products with full inventory availability, making them the primary choice for direct substitution. The difference between these variants is packaging format (Tape & Reel), which does not affect electrical performance.

Primary Alternatives (Microchip Technology):

24FC128T-I/SN and 24FC128-I/SN offer superior performance with 400 ns access time versus 550 ns, while maintaining 1 MHz clock frequency and identical memory capacity. Both are ROHS3 compliant with MSL 1 rating. These parts are pin-compatible in 8-SOIC package and represent the most direct functional upgrade path.

AT24C128C-SSHM-T provides identical 1 MHz operation and 550 ns access time matching the original part. MSL 3 rating requires controlled storage conditions (168 hours at 60% RH, 30°C maximum). This part is suitable for applications with standard moisture control procedures.

24AA128T-I/SN operates at reduced 400 kHz clock frequency with 900 ns access time. This part is suitable only for applications where lower I2C bus speed is acceptable. MSL 3 rating applies.

Alternative Manufacturers:

BR24G128FJ-3AGTE2 (Rohm Semiconductor) provides 1 MHz operation in 8-SOP-J package with MSL 1 rating and ROHS3 compliance. Package dimensions (0.154" width) match the original part.

BR24G128F-3AGTE2 (Rohm Semiconductor) offers 1 MHz operation in standard 8-SOP package with slightly wider pitch (0.173" width). Verify PCB layout compatibility before selection.

602-20012 (Parallax Inc.) provides 1 MHz operation with superior 400 ns access time in 8-SOIC package. MSL 1 rating and ROHS3 compliance confirmed.

Selection Criteria by Application:

For direct replacement without design modification: FT24C128A-ESG-T or FT24C128A-ESR-T.

For performance upgrade with faster access time: 24FC128T-I/SN or 24FC128-I/SN.

For alternative manufacturer sourcing: BR24G128FJ-3AGTE2 or 602-20012.

For cost-optimized solutions with reduced speed requirements: 24AA128T-I/SN.

Frequently Asked Questions (FAQ)

Q: Can FT24C128A-ESG-T and FT24C128A-ESR-T be used as direct drop-in replacements?

A: Yes. Both parts are parametric equivalents with identical electrical specifications, memory capacity, clock frequency, access time, voltage range, and temperature range. The only difference is packaging format (Tape & Reel). No circuit modifications are required.

Q: What is the difference between 8-SOIC and 8-SOP packages?

A: Both are 8-pin surface mount packages with 0.154" width (3.90mm) and compatible pin pitch. 8-SOIC and 8-SOP designations refer to the same physical package in this application. Verify with your PCB layout to confirm pad compatibility.

Q: Can 24FC128T-I/SN replace FT24C128A-USR-T without modification?

A: Yes, with performance improvement. 24FC128T-I/SN is pin-compatible in 8-SOIC package, maintains 1 MHz I2C operation, and provides faster 400 ns access time. No circuit changes required. Verify I2C address configuration if applicable to your design.

Q: Why do some substitutes have 400 kHz clock frequency instead of 1 MHz?

A: 24AA128T-I/SN and BR24G128F-3GTE2 are specified for 400 kHz I2C operation. These parts are compatible with systems designed for lower I2C bus speeds. They are not suitable for applications requiring 1 MHz operation.

Q: What does MSL 3 rating mean for AT24C128C-SSHM-T?

A: MSL 3 (Moisture Sensitivity Level 3) requires storage at ≤60% relative humidity and ≤30°C. The part can absorb moisture for up to 168 hours under these conditions before soldering. Standard moisture control procedures in manufacturing environments satisfy this requirement.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All listed substitute parts carry ROHS3 compliance certification, matching the original FT24C128A-USR-T specification.

Q: Which substitute offers the best performance?

A: 24FC128T-I/SN and 24FC128-I/SN provide the fastest access time (400 ns) while maintaining 1 MHz clock frequency. These parts represent performance improvement over the original 550 ns specification.

Q: Can I use BR24G128F-3GTE2 in a 1 MHz I2C application?

A: No. BR24G128F-3GTE2 is specified for 400 kHz maximum clock frequency. Using this part in a 1 MHz system will result in communication errors. Select BR24G128F-3AGTE2 or BR24G128FJ-3AGTE2 for 1 MHz operation.

Q: What is the inventory status of substitute parts?

A: FT24C128A-ESG-T (4,693 units), FT24C128A-ESR-T (15,645 units), 24FC128T-I/SN (5,400 units), and AT24C128C-SSHM-T (200,300 units) have substantial inventory. Verify current availability with your supplier before design finalization.

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