Microchip Technology 25LC256X-E/ST

Overview

25LC256X-E/ST from Microchip Technology 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 and STATUS register, self-timed 5 ms write cycles, and 1 µA standby current - deployed in embedded control systems for firmware parameter storage and calibration data retention.

For engineers reviewing the 25LC256X-E/ST datasheet, 25LC256X-E/ST pinout, 25LC256X-E/ST application, or 25LC256X-E/ST equivalent, key selection criteria include VCC range (2.5–5.5 V), TSSOP-8 package compatibility, SPI Mode 0,0/1,1 support, and block-level write protection granularity (none/¼/½/all array).

Technical Context

The 25LC256X-E/ST implements a standard SPI interface with separate SI (data in) and SO (data out) lines, requiring CS, SCK, and HOLD for full protocol compliance. Its internal architecture includes an 8-bit instruction register, page latches, and HV generator for EEPROM programming - enabling byte- and page-write operations without external high-voltage supply.

Write enable logic relies on a volatile WEL bit set by WREN and reset by WRDI, power-up, or successful WRITE/WRSR execution. Block protection is controlled nonvolatily via BP0/BP1 bits in the STATUS register, while hardware write protection engages only when WPEN = 1 and WP = low - allowing selective lockdown of STATUS register writes independent of memory array access.

Key Specifications

Pinout & Package

25LC256X-E/ST is housed in an 8-lead Thin Shrink Small Outline Package (TSSOP) with 0.65 mm pitch, 4.4 mm body width, and lead finish compliant with RoHS. Pin 1 is marked with a dot or beveled corner; orientation follows JEDEC MO-153 standard.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC256X-E/ST, 25AA256-I/ST offers broader voltage support but reduced temperature margin, while AT25SF256A-SSHD-B delivers higher bandwidth and capacity at the cost of SPI protocol compatibility and pin-level interoperability.

Availability

25LC256X-E/ST is available at Aetrix Electronics and suitable for motor control calibration storage, industrial sensor configuration, and medical device settings backup requiring stable component supply and long-term obsolescence management.

Supply support for 25LC256X-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 global semiconductor company specializing in microcontrollers, analog devices, and memory solutions for embedded systems.

The 25LC256X-E/ST belongs to Microchip's legacy 25XX256 SPI EEPROM family, designed for reliable, low-power nonvolatile data storage in resource-constrained industrial and automotive control applications.

FAQ

What is the maximum clock frequency supported by the 25LC256X-E/ST?

The 25LC256X-E/ST supports a maximum clock frequency of 10 MHz when VCC is 4.5 V to 5.5 V. At lower supply voltages (2.5 V ≤ VCC < 4.5 V), the max clock drops to 5 MHz, and at 1.8 V ≤ VCC < 2.5 V, it is limited to 3 MHz. These deratings ensure timing margin compliance across the full operating voltage range specified in DS20001822H.

Does the 25LC256X-E/ST require external high-voltage programming circuitry?

No, the 25LC256X-E/ST does not require external high-voltage programming circuitry. It integrates an internal charge pump (HV generator) that generates the necessary programming voltage from the standard 2.5–5.5 V VCC supply. All write and erase operations are fully self-timed and completed internally within 5 ms, eliminating need for external VPP or timing control logic.

How does the HOLD pin function during an active SPI transaction on the 25LC256X-E/ST?

The HOLD pin on the 25LC256X-E/ST suspends ongoing SPI communication when pulled low while SCK is low. During HOLD, SI, SCK, and SO enter high-impedance states and all inputs except CS are ignored. The device retains its internal state and resumes exactly where it left off when HOLD is raised while SCK remains low - enabling host MCUs to service urgent interrupts without retransmitting commands or addresses.

Can the 25LC256X-E/ST be used in automotive applications?

Yes, the 25LC256X-E/ST is AEC-Q100 qualified for automotive applications. It meets stress test requirements for temperature cycling, humidity bias, and ESD robustness (≥4 kV HBM), and is rated for operation across the Industrial temperature range (−40°C to +85°C), making it suitable for engine control modules, body electronics, and ADAS subsystems where nonvolatile parameter storage is required.

What happens to the write enable latch after a successful write operation on the 25LC256X-E/ST?

After a successful WRITE, WRSR, or WRDI instruction, the write enable latch (WEL bit in STATUS register) is automatically reset to '0'. This prevents unintended subsequent writes unless WREN is explicitly reissued. The latch also resets on power-up and remains disabled until the host issues a new WREN command - ensuring fail-safe behavior against spurious writes during power transitions or noise events.