Microchip Technology 24CS256T-I/OT

Overview

24CS256T-I/OT from Microchip Technology is a 256-Kbit I²C serial EEPROM organized as 32,768 × 8-bit, supporting high-speed mode up to 3.4 MHz, 1.7V–5.5V operation, built-in ECC for single-bit error correction, and a factory-programmed 128-bit unique serial number. It serves as nonvolatile configuration storage in automotive control units, industrial PLCs, and smart metering systems requiring AEC-Q100 qualification and >200-year data retention.

For engineers reviewing the 24CS256T-I/OT datasheet, 24CS256T-I/OT pinout, 24CS256T-I/OT application, or 24CS256T-I/OT equivalent, key selection criteria include I²C high-speed timing compliance (THIGH ≤ 60 ns at 3.4 MHz), dual write-protection modes (hardware WP pin + software-configurable zone lock), Security register programmability, ECC latch visibility via Configuration register, and compatibility with legacy 24AA256/24LC256 designs.

Technical Context

The 24CS256T-I/OT implements a two-wire I²C interface with Schmitt-trigger inputs, slope-controlled outputs, and support for standard (100 kHz), fast (400 kHz), fast-plus (1 MHz), and high-speed (3.4 MHz) modes. Its internal architecture separates the 256-Kbit main array from a dedicated 1-Kbit Security register containing read-only serial number and user-lockable 64-byte ID page.

Write protection is configurable via hardware (WP pin tied to VSS/VCC) or enhanced software mode using the Configuration register to lock individual 32-Kbit zones. Built-in ECC logic corrects one bit per four-byte read, with an Error Correction State (ECS) latch indicating correction events - accessible only through the Configuration register's read-only status bit.

Key Specifications

Pinout & Package

24CS256T-I/OT is supplied in an 8-lead SOT-23 package (5-pin variant, with pins A0–A2 internally fixed to logic '0' per datasheet Section 3.3.1 Note 1). This compact surface-mount package measures 2.9 mm × 1.6 mm × 1.1 mm and features wettable flank geometry for automated optical inspection (AOI) during reflow soldering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24AA256-I/OT and AT24C256C-SSHL-T, the 24CS256T-I/OT provides unique device identity, ECC-protected reads, and software-configurable write zones - making it the sole choice for automotive, medical, and secure industrial applications demanding data integrity and traceability.

Availability

24CS256T-I/OT is available at Aetrix Electronics and suitable for automotive body control modules, industrial PLCs, and smart electricity meters requiring stable component supply, AEC-Q100 qualification, and long-term lifecycle support.

Supply support for 24CS256T-I/OT 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 manufacturer specializing in microcontrollers, analog devices, and memory solutions, with global design centers and ISO/TS 16949-certified manufacturing.

The 24CS256 product line delivers high-reliability serial EEPROMs optimized for automotive, industrial, and medical applications requiring extended temperature operation, built-in ECC, and cryptographic identity features.

FAQ

What is the maximum I²C clock frequency supported by the 24CS256T-I/OT?

The 24CS256T-I/OT supports I²C High-Speed mode up to 3.4 MHz when operating at VCC ≥ 2.5V and within the Industrial temperature range (−40°C to +85°C). At lower voltages or extended temperature, the maximum clock frequency drops to 1 MHz (fast-plus mode) or 400 kHz (fast mode), as specified in Table 1-2 of the DS20005998D datasheet. The 24CS256T-I/OT must be configured for HS mode via the Configuration register before achieving 3.4 MHz operation.

Does the 24CS256T-I/OT include a factory-programmed serial number?

Yes, the 24CS256T-I/OT contains a factory-programmed, globally unique 128-bit serial number stored in the first 16 bytes of its Security register (address range 0800h–080Fh). This read-only value is guaranteed unique across the entire CS series and eliminates the need for external serialization during manufacturing. The 24CS256T-I/OT also provides an additional 64-byte user-programmable ID page that can be permanently locked via software sequence.

How does the built-in ECC function in the 24CS256T-I/OT?

The 24CS256T-I/OT implements on-die ECC that detects and corrects single-bit errors within any four-byte read window. When correction occurs, the Error Correction State (ECS) latch in the Configuration register is set and remains asserted until cleared by a read of the Configuration register. This allows host firmware to monitor data integrity in real time. The 24CS256T-I/OT does not support multi-bit error correction or reporting beyond the ECS flag.

Can the 24CS256T-I/OT replace a 24LC256 in an existing design?

The 24CS256T-I/OT is backward compatible with 24LC256 in pinout, basic I²C protocol, and memory addressing - but adds Security register access, ECC, and enhanced write protection. To retain full functionality, the host firmware must be updated to handle the extended device address map (1011xxx for Security/Configuration registers) and interpret the ECS latch. The 24CS256T-I/OT operates across the same 1.7V–5.5V range and supports identical package variants, including SOT-23.

What write protection options are available on the 24CS256T-I/OT?

The 24CS256T-I/OT offers two independent write protection mechanisms: (1) Hardware protection via the WP pin - tying WP to VCC disables all writes to both main array and Security register; (2) Enhanced software protection via the Configuration register - allowing individual 32-Kbit zones to be locked, with the Configuration register itself lockable to prevent further changes. Both modes coexist and can be used simultaneously for defense-in-depth security.