Microchip Technology 25LC256T-E/ST

Overview

25LC256T-E/ST from Microchip Technology Inc. is a 256 Kbit (32,768 × 8) SPI Serial EEPROM with 64-byte page write capability, 10 MHz max clock frequency, and industrial-grade operation from −40°C to +85°C. It features hardware write protection via WP pin, HOLD functionality for interrupt-safe bus suspension, and low-power standby current of 1 µA at 5.5 V - deployed in embedded control systems for firmware parameter storage and calibration data retention.

For engineers reviewing the 25LC256T-E/ST datasheet, 25LC256T-E/ST pinout, 25LC256T-E/ST application, or 25LC256T-E/ST equivalent, key selection criteria include its 2.5–5.5 V supply range, TSSOP-8 package compatibility, self-timed 5 ms write cycle, and AEC-Q100 qualification for automotive subsystems requiring nonvolatile configuration memory.

Technical Context

The 25LC256T-E/ST implements a standard SPI Mode 0,0 or Mode 1,1 interface with separate SI (data-in) and SO (data-out) lines, requiring only CS, SCK, SI, SO, WP, HOLD, VCC, and VSS. Its internal architecture includes an 8-bit instruction register, page latches, and high-voltage generation circuitry enabling byte/page writes without external programming voltage.

Write operations require explicit WREN instruction followed by CS high-to-low transition to initiate internal 5 ms erase/write cycle; STATUS register (RDSR/WRSR) provides real-time WIP and WEL status plus BP0/BP1 block protection control - all accessible during active write cycles without bus interruption.

Key Specifications

Pinout & Package

25LC256T-E/ST is housed in an 8-lead Thin Shrink Small Outline Package (TSSOP), 4.4 mm body width, RoHS-compliant matte tin finish, with standard JEDEC pinout orientation (pin 1 = CS, pin 2 = SO, pin 3 = WP, pin 4 = VSS, pin 5 = SI, pin 6 = SCK, pin 7 = HOLD, pin 8 = VCC).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC256T-E/ST, the 25AA256T-I/ST offers broader voltage flexibility but sacrifices automotive qualification, while the AT25SF041 provides greater density and speed at the cost of SPI protocol compatibility and HOLD functionality - making 25LC256T-E/ST optimal for cost-sensitive, AEC-Q100–required, interrupt-aware embedded systems.

Availability

25LC256T-E/ST is available at Aetrix Electronics and suitable for industrial automation, automotive electronics, and medical device applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for 25LC256T-E/ST 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 and manufacturing operations.

The 25LC256T-E/ST belongs to Microchip's 25XX256 family of SPI Serial EEPROMs, engineered for reliable nonvolatile data storage in resource-constrained embedded systems where low power, small footprint, and deterministic write timing are critical.

FAQ

What is the maximum clock frequency supported by the 25LC256T-E/ST?

The 25LC256T-E/ST supports up to 10 MHz clock frequency when VCC is 4.5–5.5 V, 5 MHz at 2.5–4.5 V, and 3 MHz at 1.8–2.5 V. This graded specification ensures timing compliance across its full 2.5–5.5 V operating range. The 25LC256T-E/ST uses standard SPI Mode 0,0 or Mode 1,1 signaling, and all AC timing parameters - including setup/hold times - scale with VCC per Table 1-2 in DS20001822H.

Does the 25LC256T-E/ST require an external voltage booster for write operations?

No, the 25LC256T-E/ST does not require an external voltage booster. It integrates an on-chip high-voltage generator that derives programming voltage internally from VCC, enabling standard 2.5–5.5 V single-supply operation. All write cycles - whether byte, page, or STATUS register - complete autonomously within the 5 ms max internal write time (TWC), with no external components needed beyond standard VCC decoupling.

How does hardware write protection work on the 25LC256T-E/ST?

Hardware write protection on the 25LC256T-E/ST is controlled jointly by the WP pin and the WPEN bit in the STATUS register. When WPEN = 1 and WP = low, writes to nonvolatile STATUS register bits (BP0, BP1, WPEN) are disabled - preventing accidental lockout of memory blocks. The 25LC256T-E/ST remains fully readable and writable to unprotected memory regions. WPEN can be cleared via WRSR to disable hardware protection and regain full STATUS register access.

Can the 25LC256T-E/ST be used in automotive applications?

Yes, the 25LC256T-E/ST is AEC-Q100 qualified for automotive applications (Grade 2: −40°C to +105°C ambient). Its qualification covers thermal cycling, humidity testing, and ESD robustness (>4 kV HBM), making it suitable for engine control modules, body electronics, and ADAS sensors. The "E" in the part number denotes Extended temperature grade, and "T-E/ST" confirms TSSOP packaging with automotive screening - verified in Microchip's DS20001822H datasheet.

What happens if a page write crosses a 64-byte boundary on the 25LC256T-E/ST?

If a page write command attempts to cross a 64-byte boundary on the 25LC256T-E/ST, data wraps around to the start of the current page instead of advancing to the next page - overwriting previously loaded bytes in that same page. This behavior is defined in Section 2.3 of DS20001822H. To prevent corruption, application firmware must validate address alignment before initiating multi-byte writes and split transfers at page boundaries - a requirement enforced by the 25LC256T-E/ST's physical page latch architecture.