Microchip Technology 24LC128-I/MS

Overview

24LC128-I/MS 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 I²C clock frequency, features hardware write-protection via the WP pin, and delivers 1 µA max standby current at industrial temperature (–40°C to +85°C). It is used in real-time configuration storage for industrial controllers and sensor calibration data retention.

For engineers reviewing the 24LC128-I/MS datasheet, 24LC128-I/MS pinout, 24LC128-I/MS application, or 24LC128-I/MS equivalent, this page provides verified electrical specs, package mapping to MSOP-8, functional pin roles, I²C timing constraints, and validated alternative parts for design continuity and supply resilience.

Technical Context

The 24LC128-I/MS implements a two-wire I²C interface with Schmitt-trigger inputs on SDA and SCL for noise immunity, slope-controlled outputs to suppress ground bounce, and a 64-byte page write buffer enabling efficient bulk writes. Its internal address counter supports sequential reads across the full 128Kbit memory space (0x0000–0x3FFF), with automatic rollover at boundary.

It uses a cascaded slave addressing scheme with three hardware-configurable chip select pins (A0–A2), allowing up to eight devices on one bus-though only two are supported in the MSOP package due to A0/A1 being no-connects. Write protection is enforced by sampling the WP pin at the Stop condition of each write command.

Key Specifications

Pinout & Package

24LC128-I/MS is packaged in an 8-lead MSOP (Micro Small Outline Package) with 0.65 mm lead pitch, body dimensions 3.0 × 3.0 × 1.0 mm, and exposed pad optional for thermal relief. Pins A0 and A1 are not connected in this variant; only A2, VSS, SDA, SCL, WP, VCC are functional.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24AA128-I/MS, the 24LC128-I/MS trades low-voltage operation for tighter industrial voltage compliance and smaller MSOP footprint; compared with 24LC128-I/SN, it sacrifices cascading flexibility for space savings and simplified routing in dense layouts.

Availability

24LC128-I/MS is available at Aetrix Electronics and suitable for industrial sensor nodes, medical device calibration storage, and smart energy metering requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 24LC128-I/MS 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 infrastructure.

The 24LC128 belongs to Microchip's 24XX128 family of I²C serial EEPROMs, engineered for robust, low-power nonvolatile storage in industrial, medical, and automotive applications where data integrity and long-term reliability are critical.

FAQ

What is the minimum VCC required for reliable operation of the 24LC128-I/MS?

The 24LC128-I/MS requires a minimum VCC of 2.5V for guaranteed operation across its full industrial temperature range (–40°C to +85°C). Unlike the 24AA128 variant, it is not specified for operation below 2.5V. Attempting to power the 24LC128-I/MS at 2.4V or lower may result in undefined behavior, failed writes, or incomplete I²C acknowledgments. Always verify VCC stability under load using a scope during system validation.

Can the 24LC128-I/MS be used interchangeably with the 24LC128-I/SN on the same PCB?

No - the 24LC128-I/MS (MSOP-8) and 24LC128-I/SN (SOIC-8) have different footprints, thermal pads, and pin connectivity: A0 and A1 are no-connects in the MSOP but functional in the SOIC. Swapping packages without redesigning the PCB will cause open-circuit errors on A0/A1 nets and potential I²C bus contention. Use only the designated package variant for which the layout was validated.

How does the WP pin function during active I²C communication with the 24LC128-I/MS?

The WP pin on the 24LC128-I/MS is sampled only at the Stop condition of each write command - not continuously. If WP is pulled high *after* the Stop bit but before the internal write cycle completes, the ongoing write proceeds unaffected. To enforce read-only mode, WP must be held high *before* issuing any write command and maintained until the next power cycle or reset. This behavior prevents accidental lockout during dynamic reconfiguration.

What is the maximum number of 24LC128-I/MS devices that can share one I²C bus?

Only two 24LC128-I/MS devices can be connected to a single I²C bus because the MSOP package has A0 and A1 as no-connects, leaving only A2 as the sole configurable chip address bit. With A2 = 0 or 1, exactly two unique slave addresses (1010 0 0 0 R/W and 1010 1 0 0 R/W) are possible. For more than two devices, use the SOIC or TSSOP variants where A0 and A1 are bonded and functional.

Does the 24LC128-I/MS support 1 MHz I²C clock frequency?

No - the 24LC128-I/MS is rated for a maximum I²C clock frequency of 400 kHz across its full VCC range (2.5V–5.5V). The 1 MHz capability is exclusive to the 24FC128 variant. Operating the 24LC128-I/MS at 1 MHz violates AC specifications (e.g., THIGH, TLOW, TR/TF), resulting in unreliable ACK generation, data corruption, or bus lockup. Always adhere to the 400 kHz limit in timing-critical systems.