Microchip Technology 24FC128-I/ST

Overview

24FC128-I/ST from Microchip Technology Inc. is a 128 Kbit (16K × 8) I²C-compatible serial EEPROM designed for low-voltage, low-power embedded systems. It operates from 1.7V to 5.5V, supports up to 1 MHz I²C clock frequency at V_CC ≥ 2.5V, features 64-byte page write buffer, hardware write-protection via WP pin, and guarantees >1 million erase/write cycles with >200 years data retention. It is used in industrial sensor calibration storage and firmware parameter backup.

For engineers reviewing the 24FC128-I/ST datasheet, 24FC128-I/ST pinout, 24FC128-I/ST application, or 24FC128-I/ST equivalent, key selection criteria include its 1 MHz I²C speed at 1.7–5.5V supply, industrial temperature range (−40°C to +85°C), SOIC-8 package compatibility, and hardware write-protect functionality for secure configuration storage.

Technical Context

The 24FC128-I/ST 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 128 Kbit memory space (0x0000–0x3FFF), and cascading support allows up to eight devices on one bus using A0–A2 address pins.

It uses self-timed erase/write cycles with automatic page buffering: up to 64 bytes are latched before initiating a single internal 5 ms write cycle. Write protection is enforced by sampling the WP pin state at the Stop condition - no write occurs if WP = V_CC, while reads remain fully functional.

Key Specifications

Pinout & Package

24FC128-I/ST is packaged in an 8-lead SOIC (SN) with 3.90 mm body width, JEDEC MS-012AC compliant, RoHS-compliant matte tin lead finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24AA128-I/ST and AT24C128-10PU-2.7, the 24FC128-I/ST uniquely delivers 1 MHz I²C performance across the full 1.7–5.5V range - enabling faster parameter loading in battery-powered edge devices while maintaining drop-in compatibility in SOIC-8 footprint designs.

Availability

24FC128-I/ST is available at Aetrix Electronics and suitable for industrial sensor calibration, medical device configuration, and smart energy metering requiring stable component supply across extended product lifecycles.

Supply support for 24FC128-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 microcontroller, analog, FPGA, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 24FC128 belongs to Microchip's 24XX128 family of I²C EEPROMs, engineered specifically for robust, low-power, and voltage-flexible nonvolatile storage in industrial, automotive, and medical applications.

FAQ

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

The 24FC128-I/ST 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, the maximum clock frequency is limited to 400 kHz. This dual-speed capability ensures compatibility with both legacy 400 kHz systems and high-throughput applications requiring faster writes - a key differentiator from the 24AA128-I/ST and 24LC128-I/ST variants.

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

Yes, the 24FC128-I/ST 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 - the datasheet specifies SDA/SCL rise time ≤300 ns at V_CC ≥ 2.5V, which must be met to ensure reliable 24FC128-I/ST communication.

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

Hardware write-protection on the 24FC128-I/ST is controlled by the WP pin: when tied to V_CC, all write operations (byte and page) are inhibited, though read operations continue normally. The WP state is sampled at the Stop condition of each write command - toggling WP during an ongoing write has no effect. This provides fail-safe protection against unintended firmware or calibration overwrites in the 24FC128-I/ST.

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

Yes, up to eight 24FC128-I/ST devices can share one I²C bus using the A0, A1, and A2 address pins to configure unique 7-bit slave addresses (1010xxx). Each pin must be hardwired to VSS or VCC - floating connections are not allowed. This enables scalable memory expansion up to 1 Mbit (eight × 128 Kbit) with contiguous addressing support in software, a capability confirmed for the 24FC128-I/ST in the device selection table.

What is the page write time specification for the 24FC128-I/ST?

The 24FC128-I/ST has a maximum page write time of 5 ms, which is self-timed and independent of host controller timing. During this period, the device does not acknowledge I²C commands - a behavior leveraged by ACK polling to detect write completion. This fixed 5 ms latency applies whether writing 1 byte or all 64 bytes in a page, ensuring predictable timing for real-time systems using the 24FC128-I/ST.