Microchip Technology 24FC256T-I/ST

Overview

24FC256T-I/ST from Microchip Technology is a 256-Kbit (32K × 8) I²C-compatible serial EEPROM with 1.7V–5.5V single-supply operation, 1 MHz maximum clock frequency at V_CC ≥ 2.5V, and industrial temperature range (–40°C to +85°C). It features a 64-byte page write buffer, hardware write-protection via WP pin, and Schmitt-trigger inputs for noise immunity - deployed in embedded system configuration storage, sensor calibration data retention, and power-meter firmware parameter backup.

For engineers reviewing the 24FC256T-I/ST datasheet, 24FC256T-I/ST pinout, 24FC256T-I/ST application, or 24FC256T-I/ST equivalent, key selection criteria include its 1 MHz I²C speed capability, 5 ms max page write time, 1 µA standby current, and ST (SOIC-8) package compatibility with legacy board layouts requiring 150-mil width and 0.150" lead pitch.

Technical Context

The 24FC256T-I/ST implements a two-wire I²C interface with standard and fast-mode timing compliance, supporting up to eight devices on one bus via A0/A1/A2 address pins. Its internal architecture includes a 64-byte page latch, HV generator for EEPROM programming, and memory control logic enabling self-timed erase/write cycles without external timing components.

It uses open-drain SDA/SCL with integrated Schmitt-trigger inputs and output slope control to suppress ground bounce and tolerate bus capacitance up to 400 pF. Write protection is hardware-enforced via the WP pin, sampled at the Stop bit of each write command, and independent of software control.

Key Specifications

Pinout & Package

24FC256T-I/ST is supplied in an 8-lead SOIC package (ST suffix), 3.90 mm body width, 150-mil lead pitch, RoHS-compliant matte tin finish. Pin 1 is marked by a beveled corner or notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24AA256T-I/ST and AT24C256-10PU-2.7, the 24FC256T-I/ST uniquely delivers 1 MHz I²C performance down to 1.7V, making it optimal for high-throughput, low-voltage embedded systems where both speed and supply flexibility are mandatory.

Availability

24FC256T-I/ST is available at Aetrix Electronics and suitable for smart metering, industrial PLCs, medical infusion pumps, and automotive body control modules requiring stable component supply, long-lifecycle support, and guaranteed RoHS-compliant manufacturing.

Supply support for 24FC256T-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, FPGA, and memory solutions, serving industrial, automotive, communications, and consumer markets with vertically integrated silicon and development tools.

The 24FC256T-I/ST belongs to Microchip's 24XX256 family of serial EEPROMs, designed specifically for low-power, space-constrained embedded systems requiring reliable nonvolatile storage with flexible voltage operation and robust I²C interoperability.

FAQ

What is the maximum I²C clock frequency supported by the 24FC256T-I/ST?

The 24FC256T-I/ST supports up to 1 MHz I²C clock frequency when V_CC is 2.5V or higher. At V_CC < 2.5V, the maximum clock rate drops to 400 kHz. This dual-speed capability allows the 24FC256T-I/ST to operate efficiently across both 1.8V and 3.3V system domains without sacrificing throughput in higher-voltage configurations.

Does the 24FC256T-I/ST require external pull-up resistors on SDA and SCL lines?

Yes, the 24FC256T-I/ST requires external pull-up resistors on both SDA and SCL because these pins are open-drain. For 1 MHz operation, a 2 kΩ pull-up to V_CC is recommended; for 400 kHz, 2.2 kΩ is typical; and for 100 kHz, 10 kΩ suffices. Proper pull-up strength ensures signal rise times meet AC specifications and avoids bus lockup under capacitive loads.

How does hardware write-protection work on the 24FC256T-I/ST?

The WP pin on the 24FC256T-I/ST provides hardware-level write inhibition: when tied to V_CC, all write operations (byte and page) are blocked while read access remains fully functional. The pin is sampled at the Stop bit of each write command, so toggling WP mid-cycle has no effect - ensuring deterministic protection during power transitions or reset events.

What is the page size and maximum page write length for the 24FC256T-I/ST?

The 24FC256T-I/ST has a fixed 64-byte page size and supports writing up to 64 bytes in a single page write operation. Attempting to write across a page boundary causes wraparound within the same page. The internal address pointer increments automatically, and the entire page undergoes an erase/write cycle - hence endurance is rated per page, not per byte.

Is the 24FC256T-I/ST compatible with standard I²C protocol implementations?

Yes, the 24FC256T-I/ST is fully compliant with standard I²C protocol definitions, including Start/Stop condition generation, 7-bit addressing with R/W bit, ACK/NACK signaling, and repeated Start support. It responds to the base address 0x50–0x57 (depending on A2/A1/A0) and supports both random and sequential read modes without requiring custom driver logic.