AT24C128B-TH-B Equivalent & Substitute Parts

Part Overview

The AT24C128B-TH-B is a 128Kbit EEPROM memory IC with I2C interface manufactured by Microchip Technology in 8-TSSOP surface mount packaging. This part is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The device operates across a wide voltage range (1.8V to 5.5V) and temperature range (-40°C to 85°C), serving applications requiring non-volatile serial memory storage.

Key Parameters

Parameter	Value
Memory Size	128Kbit
Memory Organization	16K x 8
Memory Interface	I2C
Clock Frequency	1 MHz
Access Time	550 ns
Write Cycle Time	5ms
Voltage Supply Range	1.8V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package Type	8-TSSOP
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the AT24C128B-TH-B is determined by the following critical parameters: 128Kbit memory capacity, 16K x 8 organization, I2C interface, 8-TSSOP package footprint, and operating temperature range of -40°C to 85°C. Parts are grouped into two categories based on clock frequency compatibility:

Category 1: 1 MHz Clock Frequency (Direct Functional Match) Parts operating at 1 MHz maintain identical I2C bus speed performance as the original AT24C128B-TH-B. Access time variations (400 ns to 550 ns) remain within acceptable margins for I2C protocol compliance.

Category 2: 400 kHz Clock Frequency (Reduced Speed Operation) Parts operating at 400 kHz provide functional substitution with reduced I2C bus speed. These are suitable for applications where lower clock frequency is acceptable or preferred.

All substitute parts maintain the same memory capacity, organization, package dimensions, voltage supply range, and temperature operating range as the main part.

Parameter Comparison

Part Number	Manufacturer	Clock Frequency	Access Time (ns)	Voltage Supply	Product Status	Package
AT24C128B-TH-B	Microchip Technology	1 MHz	550	1.8V ~ 5.5V	Obsolete	8-TSSOP
24AA128-I/ST	Microchip Technology	400 kHz	900	1.7V ~ 5.5V	Active	8-TSSOP
24FC128-I/ST	Microchip Technology	1 MHz	400	1.7V ~ 5.5V	Active	8-TSSOP
AT24C128C-XHM-B	Microchip Technology	1 MHz	550	1.7V ~ 5.5V	Active	8-TSSOP
BR24G128FVT-3AGE2	Rohm Semiconductor	1 MHz	Not specified	1.7V ~ 5.5V	Active	8-TSSOP-B
BR24G128FVT-3GE2	Rohm Semiconductor	400 kHz	Not specified	1.6V ~ 5.5V	Active	8-TSSOP-B
BR24S128FVT-WE2	Rohm Semiconductor	400 kHz	Not specified	1.7V ~ 5.5V	Active	8-TSSOP-B
CAT24C128YI-G	onsemi	1 MHz	400	1.8V ~ 5.5V	Obsolete	8-TSSOP
CAT24C128YI-GT3	onsemi	1 MHz	400	1.8V ~ 5.5V	Active	8-TSSOP
CAT24C128YIGT3JN	onsemi	1 MHz	400	1.8V ~ 5.5V	Active	8-TSSOP
M24128-BRDW6TP	STMicroelectronics	1 MHz	450	1.8V ~ 5.5V	Active	8-TSSOP

Engineering Selection Recommendations

For new designs and production continuity, AT24C128C-XHM-B is the primary recommended substitute. This Microchip Technology part maintains identical electrical specifications to the AT24C128B-TH-B (1 MHz clock frequency, 550 ns access time, 1.7V to 5.5V supply range) while offering active product status with extensive inventory availability (51,820 pcs). Both parts are ROHS3 compliant and carry identical REACH and ECCN classifications.

M24128-BRDW6TP from STMicroelectronics provides an alternative 1 MHz substitute with verified programmability status and high inventory levels (65,200 pcs). This part operates within the same voltage and temperature specifications with marginally faster access time (450 ns).

For applications where reduced I2C bus speed is acceptable, 24AA128-I/ST offers a cost-effective 400 kHz alternative from Microchip Technology with active product status. This part maintains the same memory capacity and package footprint.

All recommended substitutes are ROHS3 compliant and carry identical HTSUS and ECCN classifications as the original part, ensuring regulatory compliance across supply chain transitions.

Frequently Asked Questions (FAQ)

Q: Can I use a 400 kHz substitute in place of the 1 MHz AT24C128B-TH-B?

A: Yes, functionally. The 400 kHz parts (24AA128-I/ST, BR24G128FVT-3GE2, BR24S128FVT-WE2) provide full memory capacity and I2C interface compatibility. However, the I2C bus will operate at reduced speed. Verify that your system design does not require 1 MHz clock frequency operation before substitution.

Q: Are the 8-TSSOP and 8-TSSOP-B packages interchangeable?

A: Both packages maintain identical 0.173" width and 4.40mm dimensions, providing mechanical compatibility for PCB footprints. Verify with your PCB layout tool that the specific package variant matches your design requirements.

Q: What is the voltage supply difference between 1.7V and 1.8V minimum specifications?

A: The AT24C128B-TH-B specifies 1.8V minimum, while most active substitutes specify 1.7V minimum. If your design operates at voltages between 1.7V and 1.8V, select substitutes with 1.7V minimum rating. For designs operating above 1.8V, both specifications are equivalent.

Q: Why is AT24C128C-XHM-B recommended over other Microchip alternatives?

A: AT24C128C-XHM-B matches the original part's electrical specifications exactly (1 MHz, 550 ns access time) while maintaining active product status. It offers the highest inventory availability (51,820 pcs) and represents the direct successor in Microchip's product line.

Q: Are all listed substitutes ROHS3 compliant?

A: Yes. All substitute parts listed carry ROHS3 compliance status identical to the AT24C128B-TH-B, ensuring regulatory alignment for production and supply chain requirements.

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