Microchip Technology 24CS256-I/MS

Overview

24CS256-I/MS 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 integrated 128-bit factory-unique serial number. It features hardware write-protection via WP pin, built-in ECC for single-bit error correction, and AEC-Q100 qualification for automotive use.

For engineers reviewing the 24CS256-I/MS datasheet, 24CS256-I/MS pinout, 24CS256-I/MS application, or 24CS256-I/MS equivalent, key selection considerations include its 8-lead MSOP package, dual write protection (hardware + enhanced software), Security register architecture, and compatibility with legacy 24AA256/24LC256 devices in industrial and automotive systems.

Technical Context

The 24CS256-I/MS implements a two-wire I²C interface with Schmitt-trigger inputs, slope-controlled outputs, and support for standard (100 kHz/400 kHz/1 MHz) and high-speed (3.4 MHz) modes. Its memory is partitioned into a 256-Kbit main array and a dedicated 1-Kbit Security register containing a read-only 128-bit serial number and a user-programmable, lockable 64-byte ID page.

Device behavior is modulated by a Configuration register enabling zone-level software write protection across eight independent 32-Kbit regions, and an Error Correction State (ECS) latch indicating ECC invocation. The device responds to multiple address byte formats-including distinct codes for main EEPROM, Security register, Configuration register, and Manufacturer ID access-enabling secure, segmented memory management without external logic.

Key Specifications

Pinout & Package

8-Lead MSOP (Mini Small Outline Package) with exposed pad; lead pitch 0.65 mm, body size 3.0 mm × 3.0 mm × 1.1 mm. Pin 1 marked with dot; pin numbering counterclockwise from top-left corner when viewed from top.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24AA256-I/MS and AT24C256C-SSHL-T, the 24CS256-I/MS delivers differentiated value through integrated security (128-bit ID + lockable ID page), ECC-based data integrity, and automotive-grade qualification - making it the sole choice for safety- or identity-critical deployments requiring long-term data fidelity.

Availability

24CS256-I/MS is available at Aetrix Electronics and suitable for automotive telematics, industrial PLC configuration storage, and medical device settings retention requiring stable component supply, long-lifecycle support, and AEC-Q100 compliance.

Supply support for 24CS256-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 microcontroller, analog, FPGA, and memory solutions, headquartered in Chandler, Arizona, with global design, manufacturing, and sales operations.

The 24CS256-I/MS belongs to Microchip's CS-series serial EEPROM family, designed specifically for automotive, industrial, and medical applications demanding enhanced security, reliability, and long-term data retention - extending beyond basic nonvolatile storage into trusted device identity and safe parameter management.

FAQ

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

The 24CS256-I/MS supports up to 3.4 MHz in High-Speed mode when operating at VCC ≥2.5V and within the Industrial temperature range (−40°C to +85°C). At lower voltages (1.7V–2.5V) or Extended temperature range, maximum clock frequency is limited to 1 MHz. This enables faster firmware updates and real-time configuration writes compared to legacy 400 kHz EEPROMs.

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

Yes, the 24CS256-I/MS requires external pull-up resistors on both SDA and SCL lines because its I²C interface uses open-drain outputs. Recommended values are 330 Ω for 3.4 MHz operation, 2 kΩ for 1 MHz/400 kHz, and 10 kΩ for 100 kHz - selected based on bus capacitance and desired rise time. The 24CS256-I/MS itself does not integrate pull-up circuitry.

How is the 128-bit serial number in the 24CS256-I/MS accessed and used?

The 128-bit serial number resides in the read-only portion of the Security register (addresses 0800h–080Fh) and is accessed using a dedicated I²C device address byte (1011b + A2A1A0 + R/W). It is globally unique across all CS-series EEPROMs and enables zero-cost device serialization - eliminating manufacturing-line programming steps while supporting secure boot, anti-counterfeiting, and regulatory traceability in the 24CS256-I/MS.

Can the 24CS256-I/MS be used as a direct replacement for the 24LC256 in an existing design?

Yes, the 24CS256-I/MS is backward compatible with the 24LC256 and supports identical pinout, device addressing, and basic I²C command set. However, full functional equivalence requires verifying that legacy firmware does not rely on undocumented timing margins or unsupported features - and confirming that the 24CS256-I/MS's enhanced software write protection and Security register access do not conflict with existing initialization sequences.

What protection mechanisms prevent unintended writes to the 24CS256-I/MS memory array?

The 24CS256-I/MS implements dual-layer write protection: (1) Hardware-level via the WP pin - tying WP to VCC disables all writes; and (2) Software-level via the Configuration register - enabling zone-selective locking of eight independent 32-Kbit regions. Both mechanisms can be used simultaneously, and the Configuration register itself can be permanently locked to prevent further reconfiguration - ensuring robust data integrity in the 24CS256-I/MS.