Microchip Technology 25LC040AT-H/SN

Overview

25LC040AT-H/SN from Microchip Technology is a 4 kbit (512 × 8) SPI serial EEPROM with 16-byte page write capability, 2.5V–5.5V supply range, and extended temperature operation from –40°C to +150°C. It supports up to 5 MHz clock frequency, features hardware write protection via WP pin, and delivers >1 million erase/write cycles with >200 years data retention - used in automotive engine control units for calibration storage.

For engineers reviewing the 25LC040AT-H/SN datasheet, 25LC040AT-H/SN pinout, 25LC040AT-H/SN application, or 25LC040AT-H/SN equivalent, key selection criteria include high-temp SPI EEPROM compatibility, page-write timing constraints, HOLD/CS timing margins at 2.5V, and block-protection configuration via STATUS register.

Technical Context

The 25LC040AT-H/SN implements a standard SPI Mode 0,0 interface with separate SI (data-in) and SO (data-out) lines, requiring CS low and HOLD high for normal operation. Its internal architecture includes an 8-bit instruction register, page latches, and HV generator for EEPROM programming.

Write operations require explicit WREN instruction before WRITE or WRSR commands; the write enable latch resets after each successful write or on WP pin assertion. Block protection is controlled by BP0/BP1 bits in the nonvolatile STATUS register, enabling selective write-disable of 0%, 25%, 50%, or 100% of the 512-byte array.

Key Specifications

Pinout & Package

8-lead SOIC (SN package), Pb-free and RoHS compliant, body width 3.90 mm, footprint compatible with JEDEC MS-012AC.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC040AT-H/SN, 25AA040AT-I/SN trades extended temperature for wider voltage range, while AT25040B-MAHL-T offers faster clocking but omits HOLD and programmable block protection - making 25LC040AT-H/SN uniquely suited for safety-critical, high-temp, interrupt-aware embedded systems.

Availability

25LC040AT-H/SN is available at Aetrix Electronics and suitable for automotive ECU design, industrial sensor calibration, medical device parameter storage, and railway signaling modules requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for 25LC040AT-H/SN 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, and Flash-IP solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25LCXXXA family was designed specifically for high-reliability, extended-temperature SPI EEPROM applications in automotive, industrial, and medical systems where data integrity under thermal stress is non-negotiable.

FAQ

What is the maximum clock frequency supported by the 25LC040AT-H/SN at 2.5V supply?

The 25LC040AT-H/SN supports up to 3 MHz at 2.5V ≤ VCC < 4.5V, as specified in Table 1-2 AC Characteristics. This limit ensures setup/hold timing margins (e.g., Tsu = 30 ns, TCH = 150 ns) are met under worst-case process/voltage/temperature conditions. Exceeding 3 MHz at 2.5V risks read/write corruption due to insufficient data valid windows.

How does the HOLD pin function during an active SPI transaction with the 25LC040AT-H/SN?

During an active SPI sequence, pulling HOLD low (while SCK is low) pauses communication without resetting the internal state. The 25LC040AT-H/SN tri-states SO, SI, and SCK, ignores further input transitions except CS, and retains its address pointer and instruction context. Resuming requires bringing HOLD high while SCK remains low - enabling deterministic interrupt handling in real-time systems using the 25LC040AT-H/SN.

Can the 25LC040AT-H/SN be used in a 1.8V system?

No, the 25LC040AT-H/SN has a minimum VCC of 2.5V and is not characterized for reliable operation below that threshold. For 1.8V systems, Microchip's 25AA040AT-I/SN (1.8V–5.5V) is the functional alternative, though it lacks the 150°C rating of the 25LC040AT-H/SN. Using 25LC040AT-H/SN at 1.8V may result in failed writes, corrupted reads, or undefined STATUS register behavior.

What happens if a page write crosses the 16-byte boundary on the 25LC040AT-H/SN?

If a page write command attempts to write across a 16-byte boundary, the 25LC040AT-H/SN wraps the address back to the start of the current page instead of advancing to the next page. For example, writing 16 bytes starting at address 0x0F overwrites bytes 0x0F through 0x1E, then wraps to overwrite 0x10–0x1F - overwriting the first two bytes again. Firmware must enforce page alignment to prevent unintended data loss in the 25LC040AT-H/SN.

Is the 25LC040AT-H/SN pin-compatible with other devices in the 25LCXXXA family?

Yes, all 25LCXXXA devices including 25LC010A, 25LC020A, and 25LC040A share identical 8-pin SOIC (SN) packaging, pinout, and SPI interface timing. The 25LC040AT-H/SN can replace lower-density variants on the same PCB without layout changes, provided firmware accounts for the larger 512-byte address space and updated page boundaries.