Microchip Technology 24LC128-I/ST

Overview

24LC128-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 million erase/write cycles with >200 years data retention. It is used in industrial sensor calibration, medical device configuration, and power meter firmware parameter storage.

For engineers reviewing the 24LC128-I/ST datasheet, 24LC128-I/ST pinout, 24LC128-I/ST application, or 24LC128-I/ST equivalent, this page provides verified electrical specs, package mapping to SOIC-8 (ST), validated I²C timing behavior at 2.5–5.5V, confirmed 64-byte page write buffer operation, and real-world use cases in industrial and medical electronics requiring stable, long-life nonvolatile memory.

Technical Context

The 24LC128-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 architecture includes a 64-byte page latch, address pointer, and HV generator for EEPROM programming - all managed by dedicated memory control logic that handles self-timed write cycles without external timing constraints.

It supports cascaded bus topology with up to eight devices using A0/A1/A2 address pins (hardwired or microcontroller-driven), and enforces strict I²C protocol compliance including ACK polling, start/stop condition generation, and byte/page write sequencing. Write protection is active when WP = VCC, disabling writes while permitting reads.

Key Specifications

Pinout & Package

24LC128-I/ST is packaged in an 8-lead SOIC (narrow, 3.90 mm body), marked per Microchip drawing C04-057-SN Rev E. Pin 1 is top-left corner with notch or dot indicator; leads are gull-wing, matte tin-plated, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24LC128-I/ST, 24AA128-I/ST extends operational voltage down to 1.7V for battery-backed systems, while 24FC128-I/ST doubles I²C bandwidth to 1 MHz - both retain identical SOIC-8 footprint, 128 Kbit capacity, and industrial temperature rating, enabling drop-in replacement only where voltage or speed requirements align.

Availability

24LC128-I/ST is available at Aetrix Electronics and suitable for industrial sensor calibration, medical device configuration, and smart energy meter firmware requiring stable component supply, long-lifecycle support, and guaranteed RoHS-compliant sourcing.

Supply support for 24LC128-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 U.S.-based semiconductor company specializing in microcontrollers, analog devices, and memory solutions, with global manufacturing and quality certifications including ISO 9001 and AEC-Q200.

The 24LC128-I/ST belongs to Microchip's 24XX128 family of I²C EEPROMs, engineered for reliable, low-power nonvolatile storage in industrial, medical, and automotive applications demanding high endurance and extended data retention.

FAQ

What is the minimum supply voltage required for 24LC128-I/ST to operate correctly?

The 24LC128-I/ST requires a minimum V_CC of 2.5V for guaranteed operation across its full industrial temperature range (−40°C to +85°C). Below 2.5V, the device is not specified - unlike the 24AA128 variant, which supports down to 1.7V. This threshold ensures stable internal charge pump operation and EEPROM write margin. Always verify actual rail voltage under load before deploying 24LC128-I/ST in low-voltage designs.

Does 24LC128-I/ST support page write operations, and what is the maximum buffer size?

Yes, the 24LC128-I/ST supports page write operations with a 64-byte page buffer. This allows up to 64 bytes to be loaded into the internal latch and written to memory with a single Stop condition - significantly improving write efficiency versus byte-by-byte writes. However, page boundaries are fixed at 64-byte intervals (e.g., 0x00–0x3F), and crossing them causes wraparound; firmware must enforce alignment to avoid data corruption.

How does the WP pin function on the 24LC128-I/ST, and when is it sampled?

The WP (Write-Protect) pin on the 24LC128-I/ST is sampled at the Stop bit of each write command. When tied to VCC, it disables all write operations (byte and page) while allowing unrestricted reads. Toggling WP after the Stop bit has no effect on an ongoing write cycle. This hardware-level protection ensures configuration integrity even during unexpected resets or firmware faults - a key safety feature in medical and industrial 24LC128-I/ST deployments.

Can multiple 24LC128-I/ST devices share the same I²C bus, and how many are supported?

Yes, up to eight 24LC128-I/ST devices can share a single I²C bus using the A0, A1, and A2 address pins to configure unique 3-bit slave addresses. Each pin must be hardwired to VSS or VCC to set its logic level. For example, grounding all three yields address 0x50; setting A0=VCC gives 0x51. This enables scalable memory expansion - e.g., aggregating 1 Mbit total capacity - without requiring additional I²C controllers or multiplexers.

What is the endurance specification for 24LC128-I/ST, and how is it measured?

The 24LC128-I/ST is rated for 1,000,000 erase/write cycles per memory location, tested at 25°C and 5.5V using page-mode writes. Endurance is specified per page (64 bytes), not per byte, because page writes refresh the entire physical page - meaning frequent writes to a single address still consume one full page-cycle budget. This reflects real-world usage where firmware typically updates blocks of related parameters, not isolated bytes.