Microchip Technology 24CS256T-E/SM

Overview

24CS256T-E/SM 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, and built-in ECC for single-bit error correction. It integrates a factory-programmed 128-bit serial number and user-lockable 64-byte ID page, targeting automotive infotainment storage and industrial sensor calibration data retention.

For engineers reviewing the 24CS256T-E/SM datasheet, 24CS256T-E/SM pinout, 24CS256T-E/SM application, or 24CS256T-E/SM equivalent, key selection criteria include I²C high-speed timing compliance (THIGH ≤ 60 ns at 3.4 MHz), hardware/software write protection flexibility, ECC latch visibility via Configuration register, and AEC-Q100 qualification for under-hood deployment.

Technical Context

The 24CS256T-E/SM implements a two-wire I²C interface with Schmitt-trigger inputs and slope-controlled outputs to suppress ground bounce and noise. 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 addressing uses three hardware pins (A0–A2) to support up to eight devices on one bus, with distinct address byte formats for main EEPROM (1010xxxA), Security register (1011xxxA), and Manufacturer ID (1111100R/W). Write operations are self-timed (≤5 ms), and the Configuration register enables permanent locking of enhanced software write protection per 32-Kbit zone.

Key Specifications

Pinout & Package

24CS256T-E/SM is packaged in an 8-lead UDFN (2 mm × 3 mm, wettable flank) with exposed pad. Pin functions are electrically identical across all 8-lead packages but physically mapped per footprint.

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 24CS256T-E/SM delivers differentiated value through AEC-Q100 qualification, ECC-corrected reads, and factory-programmed uniqueness - enabling robust, traceable, and future-proof nonvolatile storage in safety-critical systems.

Availability

24CS256T-E/SM is available at Aetrix Electronics and suitable for automotive infotainment, industrial sensor calibration, and medical diagnostic equipment requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for 24CS256T-E/SM 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, FPGA, and memory solutions, serving automotive, industrial, and communications markets with vertically integrated silicon and software.

The 24CS256T-E/SM belongs to Microchip's CS-series serial EEPROM family, designed specifically for automotive-grade reliability, secure identity management, and high-speed I²C interoperability in harsh-environment embedded systems.

FAQ

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

The 24CS256T-E/SM supports up to 3.4 MHz in High-Speed mode when VCC is 2.5V–5.5V and ambient temperature is within the Industrial range (−40°C to +85°C). At Extended temperature (−40°C to +125°C), the maximum clock frequency is 1 MHz. Timing parameters such as THIGH (60 ns min) and TLOW (160 ns min) must be strictly met to maintain reliable communication at 3.4 MHz. The 24CS256T-E/SM includes output slope control to ensure signal integrity at this speed.

Does the 24CS256T-E/SM include error correction, and how does it work?

Yes, the 24CS256T-E/SM incorporates built-in Error Correction Code (ECC) logic that corrects up to one incorrectly read bit within any four-byte readout. When ECC correction is invoked, the read-only Error Correction State (ECS) latch in the Configuration register is set, allowing firmware to detect and log correction events. This capability enhances data integrity for critical applications like automotive calibration storage, where undetected bit errors could compromise system behavior. The 24CS256T-E/SM does not perform write-time ECC encoding - correction applies only to read operations.

How is the 128-bit serial number implemented in the 24CS256T-E/SM?

The 128-bit serial number in the 24CS256T-E/SM is factory-programmed into the first 16 bytes (0800h–080Fh) of the Security register and is read-only across the device's lifetime. It is globally unique across the entire CS-series EEPROM family and assigned at wafer sort, eliminating the need for post-production serialization. Access requires sending the dedicated Security register device address (1011xxxA) followed by appropriate word address bytes. The 24CS256T-E/SM does not allow modification, erasure, or duplication of this serial number - it serves as a hardware root of trust for device authentication and traceability.

Can the 24CS256T-E/SM be used with a 1.8V I²C bus?

Yes, the 24CS256T-E/SM operates across 1.7V–5.5V, making it fully compatible with 1.8V I²C buses. At 1.8V, the maximum supported clock frequency is 1 MHz (not 3.4 MHz), and DC parameters such as VIH (≥1.26V) and VIL (≤0.54V) remain valid. Pull-up resistors must be selected accordingly - typically 10 kΩ for 100 kHz, 2 kΩ for 400 kHz, and 1 kΩ for 1 MHz operation. The Schmitt-trigger inputs ensure noise immunity even at reduced voltage margins, and the 24CS256T-E/SM maintains full functionality including ECC, Security register access, and write protection modes at 1.8V.

What write protection options are available on the 24CS256T-E/SM?

The 24CS256T-E/SM offers dual write protection: (1) Hardware protection via the WP pin - tying WP to VCC disables all writes to both main memory and Security register; (2) Enhanced software protection configured via the writable Configuration register, which allows independent locking of any of eight 32-Kbit zones. Once the Configuration register is locked, its settings become permanent and immutable. These mechanisms coexist - WP pin override takes precedence, but software protection remains active when WP = VSS. This layered approach enables flexible security policies, from full-array lockdown during field service to granular zone protection for firmware partitioning.