Microchip Technology 24LC128T-I/ST

Overview

24LC128T-I/ST from Microchip Technology Inc. is a 128 Kbit (16K × 8) I²C-compatible serial EEPROM designed for nonvolatile data storage in low-power embedded systems. It operates from 2.5V to 5.5V, supports up to 400 kHz clock frequency, features hardware write-protection via the WP pin, and delivers 1 µA standby current at industrial temperature range (–40°C to +85°C). It is commonly used in set-top boxes, smart meters, and industrial controllers for parameter retention and firmware configuration.

For engineers reviewing the 24LC128T-I/ST datasheet, 24LC128T-I/ST pinout, 24LC128T-I/ST application, or 24LC128T-I/ST equivalent, key selection criteria include its 2.5V minimum VCC, 64-byte page write buffer, Schmitt-triggered SDA/SCL inputs for noise immunity, and compatibility with standard I²C master controllers across automotive, industrial, and consumer platforms.

Technical Context

The 24LC128T-I/ST implements a two-wire I²C interface with slave-only operation, using A0–A2 address pins to support up to eight devices on a shared bus. Its internal architecture includes a 64-byte page latch, HV generator for EEPROM programming, and memory control logic that enforces self-timed erase/write cycles.

It uses open-drain SDA/SCL with external pull-ups, requires no external clock source, and relies on master-generated Start/Stop conditions and ACK polling to manage write completion. The device samples the WP pin at the Stop bit to enable or disable writes, and supports byte- and page-write modes with automatic address incrementing.

Key Specifications

Pinout & Package

24LC128T-I/ST is packaged in an 8-lead SOIC (SN) with 3.90 mm body width, RoHS-compliant matte tin plating, and JEDEC-standard footprint. Pin 1 is marked by a beveled corner or dot; package dimensions conform to Microchip drawing C04-057-SN Rev E.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar serial EEPROM applications.

Compared with 24AA128T-I/ST, the 24LC128T-I/ST provides higher minimum VCC (2.5V vs. 1.7V) but identical packaging, pinout, and I²C timing-making it ideal for stable 3.3V/5V systems where ultra-low-voltage operation is unnecessary. Versus AT24C128-10PU-2.7, it adds AEC-Q100 qualification and broader factory programming support for automotive traceability.

Availability

24LC128T-I/ST is available at Aetrix Electronics and suitable for smart energy meters, industrial PLC modules, and automotive body control units requiring stable component supply, long-term lifecycle support, and RoHS-compliant manufacturing.

Supply support for 24LC128T-I/ST includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Microchip Technology Inc. is a leading provider of microcontrollers, analog components, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 24XX128 family-including 24LC128T-I/ST-is engineered for robust, low-power nonvolatile storage in industrial, automotive, and communications equipment where data integrity, endurance, and I²C interoperability are critical.

FAQ

What is the minimum supply voltage required for reliable operation of the 24LC128T-I/ST?

The 24LC128T-I/ST requires a minimum VCC of 2.5V for guaranteed operation across its full industrial temperature range (–40°C to +85°C). Below 2.5V, functionality is not specified; for sub-2.5V applications, consider the 24AA128T-I/ST variant instead. This 2.5V threshold ensures stable internal charge pump operation and EEPROM write verification.

How does the WP pin function on the 24LC128T-I/ST, and when is it sampled?

The WP (Write-Protect) pin on the 24LC128T-I/ST is sampled at the Stop condition of each write command. When tied to VCC, it disables all write operations (byte and page) while allowing unlimited reads. Toggling WP after the Stop bit has no effect-the state is latched only once per command. This enables secure, hardware-level protection of critical configuration data.

Can the 24LC128T-I/ST perform sequential reads across the full 128 Kbit address space?

Yes, the 24LC128T-I/ST supports sequential reads across the entire 0x0000–0x3FFF address range. After issuing a Start condition and control byte with R/W=1, the device transmits data bytes continuously, auto-incrementing its internal address pointer. Upon reaching address 0x3FFF, the pointer rolls over to 0x0000, enabling seamless wraparound reads without host intervention.

What is the maximum number of 24LC128T-I/ST devices that can be cascaded on a single I²C bus?

Up to eight 24LC128T-I/ST devices can be cascaded on one I²C bus using the A0, A1, and A2 address pins to configure unique 3-bit chip addresses (0x50–0x57). Each pin must be hardwired to VSS or VCC-floating connections are undefined. For the SOIC package used in 24LC128T-I/ST, all three address pins are functional and required for full 8-device support.

Does the 24LC128T-I/ST support 1 MHz I²C clock frequency?

No, the 24LC128T-I/ST supports a maximum clock frequency of 400 kHz at VCC ≥ 2.5V. The 1 MHz capability is exclusive to the 24FC128 variant. Attempting 1 MHz operation on the 24LC128T-I/ST will result in timing violations, failed ACKs, and unreliable communication-designs requiring 1 MHz should migrate to the 24FC128T-I/ST or equivalent.