Microchip Technology 24CS256-I/SN

Overview

24CS256-I/SN from Microchip Technology is a 256-Kbit I²C serial EEPROM organized as 32,768 × 8-bit, supporting byte/page writes (up to 64 bytes), self-timed write cycles ≤5 ms, and high-speed I²C up to 3.4 MHz. It features a factory-programmed 128-bit serial number, user-lockable 64-byte ID page, built-in ECC for single-bit error correction, and hardware/software write protection - deployed in automotive infotainment control modules for firmware parameter storage.

For engineers reviewing the 24CS256-I/SN datasheet, 24CS256-I/SN pinout, 24CS256-I/SN application, or 24CS256-I/SN equivalent, key selection considerations include its 1.7V–5.5V operating range, AEC-Q100 qualification, industrial temperature rating (−40°C to +85°C), 8-lead SOIC package with WP/SDA/SCL/A0–A2 pinout, and dual write-protection modes (hardware pin + configurable zone locking).

Technical Context

The 24CS256-I/SN implements a two-wire I²C interface with Schmitt-trigger inputs, slope-controlled outputs, and support for standard (100/400 kHz), fast (1 MHz), and high-speed (3.4 MHz) modes. Its memory architecture comprises a 256-Kbit main array (0000h–7FFFh) and a separate 1-Kbit security register containing read-only serial number (0800h–080Fh) and programmable ID page (0840h–087Fh).

Device operation is governed by three dedicated registers: Configuration register (enables enhanced software write protection per 32-Kbit zone and locks after programming), Security register (supports permanent lock of user ID page), and Manufacturer ID register (24-bit read-only value compliant with I²C manufacturer ID protocol). ECC logic corrects up to one bit per four-byte read, with Error Correction State (ECS) latch accessible via Configuration register.

Key Specifications

Pinout & Package

24CS256-I/SN is supplied in an 8-lead SOIC (Small Outline Integrated Circuit) package with gull-wing leads, 1.27 mm pitch, and RoHS-compliant matte tin finish. Pin 1 is marked with a beveled corner or dot.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT24C256C-SSHL-T and 24AA256-I/SN, the 24CS256-I/SN delivers differentiated value through integrated ECC, factory-serialized identity, AEC-Q100 validation, and flexible dual-mode write protection - making it the only option qualified for functional safety-aware automotive and medical applications requiring data integrity assurance.

Availability

24CS256-I/SN is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial PLCs, medical infusion pumps, and smart energy meters requiring stable component supply across multi-year production programs.

Supply support for 24CS256-I/SN 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 24CS256-I/SN belongs to Microchip's CS-series serial EEPROM family, engineered specifically for automotive and industrial applications demanding high reliability, secure identity, and extended data retention - addressing needs beyond basic nonvolatile storage.

FAQ

What is the maximum I²C clock frequency supported by the 24CS256-I/SN?

The 24CS256-I/SN supports I²C High-Speed mode up to 3.4 MHz when VCC ≥ 2.5V and operating in Industrial temperature range. At lower voltages (1.7V–2.5V), maximum clock frequency is 1 MHz. This enables faster firmware updates and configuration loads compared to legacy 400 kHz EEPROMs, while maintaining backward compatibility with standard I²C peripherals.

Does the 24CS256-I/SN require external pull-up resistors on SDA and SCL lines?

Yes, the 24CS256-I/SN requires external pull-up resistors on both SDA and SCL lines because its I/O pins are open-drain. Recommended values are 2 kΩ for 1 MHz operation and 330 Ω for 3.4 MHz High-Speed mode. Pull-up voltage must match the host MCU's I/O voltage (e.g., 3.3V or 5V) and be decoupled locally to minimize noise coupling into the 24CS256-I/SN's Schmitt-trigger inputs.

How does the hardware Write-Protect (WP) pin interact with the enhanced software write protection feature?

When the WP pin is tied to VCC, it overrides all software-based protections and disables writes to both the main memory array and security register - regardless of Configuration register settings. When WP is tied to VSS, software write protection becomes active and allows selective locking of eight 32-Kbit zones. This dual-layer scheme ensures fail-safe protection during power-up or fault conditions.

Can the 128-bit serial number in the 24CS256-I/SN be rewritten or erased?

No, the 128-bit serial number in the 24CS256-I/SN is factory-programmed and permanently read-only, located in the security register at addresses 0800h–080Fh. It cannot be altered, erased, or reprogrammed by any command sequence. This guarantees globally unique, tamper-proof device identification essential for anti-counterfeiting and regulatory traceability in automotive and medical applications.

What happens if a write operation is attempted while the 24CS256-I/SN is executing an internal self-timed write cycle?

If a write command is sent to the 24CS256-I/SN while it is busy with an internal write cycle (indicated by SDA remaining low after a Start condition), the device will not acknowledge the device address byte and will ignore the command. Host firmware must poll the device using repeated Start + device address until ACK is received, or wait the maximum 5 ms TWC before issuing new commands - ensuring data integrity and preventing bus contention.