Microchip Technology 24LC256T-I/SNG

Overview

24LC256T-I/SNG from Microchip Technology is a 256-Kbit (32K × 8) I²C-compatible serial EEPROM with hardware write-protection, 64-byte page write buffer, and operation across 2.5V–5.5V supply. It supports up to 400 kHz clock frequency at industrial temperature (−40°C to +85°C) and delivers ≤3 mA write current and ≤1 µA standby current. Used in embedded systems for parameter storage, calibration data retention, and firmware configuration in industrial controllers.

For engineers reviewing the 24LC256T-I/SNG datasheet, 24LC256T-I/SNG pinout, 24LC256T-I/SNG application, or 24LC256T-I/SNG equivalent, key selection criteria include VCC range compatibility (2.5V min), I²C timing compliance at 400 kHz, WP pin behavior under logic-high write-inhibit, and 64-byte page boundary handling during burst writes.

Technical Context

The 24LC256T-I/SNG implements a two-wire I²C interface with Schmitt-trigger inputs on SDA and SCL for noise immunity, slope-controlled outputs to suppress ground bounce, and internal address pointer auto-increment for sequential reads. Its EEPROM array uses floating-gate technology enabling >1 million erase/write cycles and >200 years of data retention.

It supports cascaded bus topology via three hardware-configurable chip-select pins (A0–A2), allowing up to eight devices on one I²C bus. The device performs self-timed byte and page write operations with maximum 5 ms cycle time and acknowledges only after completion-enabling reliable ACK polling for host synchronization.

Key Specifications

Pinout & Package

24LC256T-I/SNG is packaged in an 8-lead SOIC (Small Outline Integrated Circuit) with gull-wing leads and standard 150 mil body width. Pin 1 is marked by a beveled corner or notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24LC256T-I/SNG, the 24AA256-I/SN extends supply flexibility at the cost of clock rate headroom, while the AT24C256-10PU-2.7 trades vendor-specific timing guarantees for raw bandwidth - both require layout reuse but firmware timing validation.

Availability

24LC256T-I/SNG is available at Aetrix Electronics and suitable for industrial sensor calibration, medical device configuration, automotive body control modules, and smart energy metering requiring stable component supply across extended product lifecycles.

Supply support for 24LC256T-I/SNG 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 industrial, automotive, and consumer markets with vertically integrated silicon and software tools.

The 24LC256T-I/SNG belongs to Microchip's 24XX256 family of I²C serial EEPROMs, designed specifically for low-power, space-constrained embedded systems needing reliable, long-life nonvolatile storage with minimal pin count and firmware overhead.

FAQ

What is the minimum supply voltage required for reliable operation of the 24LC256T-I/SNG?

The 24LC256T-I/SNG requires a minimum VCC of 2.5V for full specification compliance, including 400 kHz I²C operation and guaranteed write functionality. Operation below 2.5V is not supported - unlike the 24AA256 variant, which operates down to 1.7V. This makes the 24LC256T-I/SNG appropriate for systems with regulated 3.3V or 5V rails but unsuitable for direct connection to single-cell Li-ion or alkaline battery sources without regulation. Always verify VCC stability during brown-out conditions, as the 24LC256T-I/SNG lacks built-in reset or voltage-monitoring circuitry.

How does the WP pin function on the 24LC256T-I/SNG, and when is it sampled?

The WP (Write-Protect) pin on the 24LC256T-I/SNG is sampled at the Stop condition of each write command - not continuously. When pulled high (to VCC), it inhibits all write operations (byte and page) while permitting unlimited read access. Toggling WP during an active write cycle has no effect; only the state at the Stop bit determines whether the write proceeds. This behavior allows safe runtime protection in systems where WP is controlled by a supervisor IC or GPIO, and ensures that accidental WP glitches do not corrupt ongoing writes. The 24LC256T-I/SNG acknowledges write commands even when WP is high, so host firmware must verify success via ACK polling or status checks.

Can the 24LC256T-I/SNG perform page writes across physical page boundaries?

No, the 24LC256T-I/SNG cannot perform page writes across physical page boundaries. Its 64-byte page buffer wraps around within the same 64-byte boundary - for example, writing 65 bytes starting at address 0x003F will overwrite bytes 0x0000–0x0000 instead of continuing into page 0x0040. This behavior is inherent to the internal address counter and is documented in Section 6.3 of the datasheet. Application firmware must explicitly split multi-page writes at 64-byte intervals. Failure to do so results in unintended data corruption, not an error flag or NACK. The 24LC256T-I/SNG provides no hardware detection or reporting of boundary violations.

What is the maximum I²C clock frequency supported by the 24LC256T-I/SNG, and under what conditions?

The 24LC256T-I/SNG supports a maximum I²C clock frequency of 400 kHz when VCC is ≥2.5V and ambient temperature is within the industrial range (−40°C to +85°C). It does not support 1 MHz operation - that capability is exclusive to the 24FC256 variant. At VCC < 2.5V, the 24LC256T-I/SNG is not rated for operation. Timing parameters such as THIGH, TLOW, and TR are specified only for 400 kHz under these conditions, and exceeding them risks setup/hold violations or incomplete ACK generation. Host systems must adhere strictly to Table 1-2 AC characteristics to ensure interoperability.

How many devices can be connected to the same I²C bus using the 24LC256T-I/SNG, and how is addressing managed?

Up to eight 24LC256T-I/SNG devices can be connected to a single I²C bus using the A0, A1, and A2 hardware address pins. Each pin accepts logic high or low, forming a 3-bit chip address that combines with the fixed '1010' control code to produce a unique 7-bit I²C client address. All three pins must be hard-wired to VCC or VSS - floating is undefined. The 24LC256T-I/SNG does not support dynamic address assignment or software-configurable addressing. In multi-device configurations, firmware must manage separate address offsets and avoid cross-device page-boundary writes, as contiguous addressing across devices is not supported for sequential reads.