Microchip Technology 24FC128-I/SM

Overview

24FC128-I/SM from Microchip Technology Inc. is a 128 Kbit (16K × 8) I²C-compatible serial EEPROM designed for low-voltage embedded systems. It operates from 1.7V to 5.5V, supports up to 1 MHz clock frequency at V_CC ≥ 2.5V, features hardware write-protection via the WP pin, and delivers 64-byte page write capability with ≤5 ms self-timed write cycle - used in industrial sensor calibration storage and firmware parameter retention.

For engineers reviewing the 24FC128-I/SM datasheet, 24FC128-I/SM pinout, 24FC128-I/SM application, or 24FC128-I/SM equivalent, key selection criteria include its 1 MHz I²C speed at 2.5–5.5V, industrial temperature range (−40°C to +85°C), SOIC-8 (SM) package compatibility, and hardware write-protect functionality for secure configuration data storage.

Technical Context

The 24FC128-I/SM implements a two-wire I²C interface with Schmitt-trigger inputs on SDA/SCL for noise immunity and slope-controlled outputs to suppress ground bounce. Its internal address counter enables sequential reads across the full 128Kbit memory space, while cascading support for up to eight devices on one bus uses A0–A2 address pins to form the slave address.

It integrates a 64-byte page write buffer and self-timed erase/write logic that eliminates external timing control. Write protection is enforced by sampling the WP pin at the Stop condition, and acknowledge polling is supported to detect write completion without fixed delays.

Key Specifications

Pinout & Package

24FC128-I/SM is packaged in an 8-lead SOIC (Small Outline Integrated Circuit) with 3.90 mm body width, JEDEC MS-012AC compliant, moisture sensitivity level (MSL) 1, and Pb-free matte tin finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24AA128-I/SM, the 24FC128-I/SM delivers 2.5× faster I²C writes at same voltage, while AT24C128N lacks hardware WP - making 24FC128-I/SM optimal for safety-critical, high-throughput, or low-voltage industrial designs.

Availability

24FC128-I/SM is available at Aetrix Electronics and suitable for industrial sensor calibration storage, medical device safety parameter vaults, and automotive body control module settings requiring stable component supply across extended product lifecycles.

Supply support for 24FC128-I/SM 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, FPGA, and memory solutions, serving industrial, automotive, and consumer markets with high-reliability silicon and development tools.

The 24FC128 belongs to Microchip's 24XX128 family of I²C EEPROMs engineered for ultra-low-voltage operation and robust noise immunity in harsh embedded environments.

FAQ

What is the maximum I²C clock frequency supported by the 24FC128-I/SM?

The 24FC128-I/SM supports up to 1 MHz I²C clock frequency when V_CC is 2.5V or higher. At V_CC between 1.7V and 2.5V, maximum clock frequency drops to 400 kHz. This dual-speed capability allows the 24FC128-I/SM to maintain high throughput in 3.3V/5V systems while remaining functional in 1.8V domains - a key differentiator from the 24AA128-I/SM and 24LC128-I/SM variants.

Does the 24FC128-I/SM require external pull-up resistors on SDA and SCL lines?

Yes, the 24FC128-I/SM requires external pull-up resistors on both SDA and SCL lines because these pins are open-drain. Recommended values are 2 kΩ for 1 MHz operation and 10 kΩ for 100 kHz. The exact value depends on bus capacitance and desired rise time; insufficient pull-up strength causes I²C communication failures, especially at higher frequencies. This requirement applies identically across all 24XX128 family members including the 24FC128-I/SM.

How does hardware write-protection work on the 24FC128-I/SM?

Hardware write-protection on the 24FC128-I/SM is controlled by the WP (Write-Protect) pin: when tied to VCC, all write operations (byte and page) are inhibited while read operations remain fully functional. The WP state is sampled at the Stop condition of each write command, so toggling WP mid-cycle has no effect. This behavior is identical across the 24XX128 family and provides deterministic, glitch-immune protection - unlike software lock bits used in alternatives such as the AT24C128N.

Can multiple 24FC128-I/SM devices share the same I²C bus?

Yes, up to eight 24FC128-I/SM devices can share one I²C bus using the A0, A1, and A2 address pins to configure unique 3-bit chip addresses. Each device must have a distinct combination of A0–A2 tied to VSS or VCC. For the SOIC-8 (SM) package used in 24FC128-I/SM, all three pins are functional - enabling full 8-device addressing. This allows expansion to 1 Mbit total EEPROM capacity without additional buses or multiplexers.

What is the page write buffer size and how does it affect performance of the 24FC128-I/SM?

The 24FC128-I/SM features a 64-byte page write buffer, meaning up to 64 bytes can be loaded into the buffer and written to memory in a single self-timed cycle (≤5 ms). This reduces I²C transaction overhead by 64× compared to byte-write mode, significantly accelerating bulk parameter updates. Because the buffer is physically aligned to 64-byte boundaries, crossing a page boundary wraps data within the same page - a constraint requiring firmware awareness but not present in byte-write mode.