Microchip Technology 24CS256T-E/SN66KVAO

Overview

24CS256T-E/SN66KVAO from Microchip Technology is a 256-Kbit I²C serial EEPROM organized as 32,768 × 8-bit, supporting byte/page writes (up to 64 bytes), 3.4 MHz High-Speed I²C mode, and built-in ECC for single-bit error correction. It features a factory-programmed 128-bit unique serial number and user-lockable 64-byte ID page, operating from 1.7V to 5.5V across –40°C to +125°C for automotive and industrial data logging.

For engineers reviewing the 24CS256T-E/SN66KVAO datasheet, 24CS256T-E/SN66KVAO pinout, 24CS256T-E/SN66KVAO application, or 24CS256T-E/SN66KVAO equivalent, key selection considerations include its AEC-Q100 qualification, dual write-protection modes (hardware WP pin + software-configurable zone protection), 1 µA standby current at 5.5V, and compatibility with legacy 24AA256/24LC256 devices.

Technical Context

The 24CS256T-E/SN66KVAO implements a two-wire I²C interface with Schmitt-trigger inputs, slope-controlled outputs, and programmable High-Speed mode (3.4 MHz) for fast firmware parameter storage. Its memory architecture separates the main 256-Kbit array from a dedicated 1-Kbit Security register containing read-only serial number and lockable user ID space.

It integrates a Configuration register enabling per-zone (eight 32-Kbit blocks) software write protection, which can be permanently locked; an Error Correction State (ECS) latch reports ECC invocation; and Manufacturer ID support enables system-level device identification without external logic.

Key Specifications

Pinout & Package

24CS256T-E/SN66KVAO is packaged in an 8-lead SOIC (Small Outline Integrated Circuit) with standard 150-mil body width and gull-wing leads. This surface-mount package supports automated assembly and provides mechanical robustness for high-vibration environments.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24AA256-I/P and AT24C256C-SSHL-T, the 24CS256T-E/SN66KVAO delivers differentiated value through integrated ECC, factory-unique serialization, and AEC-Q100 qualification - making it the only option among the three suitable for automotive safety-critical parameter storage and secure device identity management.

Availability

24CS256T-E/SN66KVAO is available at Aetrix Electronics and suitable for automotive telematics, industrial PLCs, and medical sensor calibration requiring stable component supply, long-term lifecycle assurance, and AEC-Q100-compliant sourcing.

Supply support for 24CS256T-E/SN66KVAO 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, serving automotive, industrial, communications, and consumer markets with vertically integrated silicon and software platforms.

The 24CS256 series was designed specifically for high-reliability, secure nonvolatile storage in automotive and industrial applications - integrating ECC, serialization, and flexible write protection to replace discrete security + memory subsystems.

FAQ

What is the maximum I²C clock frequency supported by the 24CS256T-E/SN66KVAO?

The 24CS256T-E/SN66KVAO supports High-Speed I²C mode up to 3.4 MHz when VCC is ≥2.5V and ambient temperature is within the Industrial range (–40°C to +85°C). At lower voltages or Extended temperature (–40°C to +125°C), the maximum clock frequency is 1 MHz. This enables faster firmware parameter loading in time-critical boot sequences while maintaining robustness across voltage and thermal conditions.

Does the 24CS256T-E/SN66KVAO include error correction capabilities?

Yes, the 24CS256T-E/SN66KVAO incorporates built-in Error Correction Code (ECC) logic that corrects up to one incorrectly read bit within any four-byte readout. The Configuration register includes a read-only Error Correction State (ECS) latch that is set whenever ECC correction is invoked - allowing host firmware to detect and log potential memory degradation events before failure.

How does the Security register in the 24CS256T-E/SN66KVAO function?

The 24CS256T-E/SN66KVAO Security register is a dedicated 1-Kbit space: the first 16 bytes contain a factory-programmed, globally unique 128-bit serial number (read-only), and the next 64 bytes form a user-programmable, lockable ID page. Once locked via software sequence, this ID page becomes immutable - ideal for storing cryptographic keys, calibration certificates, or device-specific identifiers in regulated environments.

Is the 24CS256T-E/SN66KVAO pin-compatible with older Microchip EEPROMs like the 24LC256?

Yes, the 24CS256T-E/SN66KVAO is backward compatible with 24AA256/24LC256/24FC256 devices in the same SOIC-8 package. Pin assignments (A0–A2, VSS, SDA, SCL, WP, VCC) match exactly, and the I²C protocol remains identical. However, advanced features like the Security register and ECC require updated host firmware to access - legacy code will operate unchanged but without new functionality.

What write protection options does the 24CS256T-E/SN66KVAO offer?

The 24CS256T-E/SN66KVAO provides dual write protection: (1) hardware-based via the WP pin (tie to VCC to disable all writes), and (2) software-configurable via the Configuration register, which enables independent protection of any of eight 32-Kbit memory zones. Once configured, the Configuration register itself can be permanently locked - ensuring persistent, tamper-resistant protection settings across power cycles.