Microchip Technology AT28C040-25FI

Overview

AT28C040-25FI from Atmel is a 4-Mbit (512K × 8) paged parallel EEPROM with JEDEC-standard byte-wide pinout, 250 ns read access time, and 10 ms maximum page write cycle time. It operates on single 5V ±10% supply, supports hardware/software data protection, and is rated for industrial temperature range (–40°C to +85°C), commonly used in firmware storage and configuration retention for embedded controllers.

For engineers reviewing the AT28C040-25FI datasheet, AT28C040-25FI pinout, AT28C040-25FI application, or AT28C040-25FI equivalent, key selection considerations include its 256-byte page write capability, DATA polling and toggle-bit write completion detection, CMOS/TTL compatibility, and LCC-44 ceramic package with side-braze construction.

Technical Context

The AT28C040-25FI implements a paged parallel EEPROM architecture with internal 256-byte latching register and autonomous write timing control. Its operation mimics static RAM for reads and supports both byte and page writes without external timing circuitry.

Write completion is verified via I/O7 DATA polling (complement-to-data behavior) or I/O6 toggle-bit detection, eliminating need for fixed delay timers. Hardware protection includes VCC sense (<3.8 V inhibit), 5 ms power-on delay, and noise filtering on WE/CE inputs.

Key Specifications

Pinout & Package

AT28C040-25FI is housed in a 44-pad ceramic leadless chip carrier (LCC), MIL-STD-1835 C-5 / JEDEC MO-115 compliant, with side-braze construction and no windowed lid. Pin 1 is marked by a corner chamfer and dot; top view orientation follows JEDEC standard.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT28C040-25LI, the AT28C040-25FI offers identical electrical performance but adds SL703 traceability; versus MX28F400BC-TI, it provides true byte/page write flexibility and deterministic write completion signaling essential for real-time embedded systems.

Availability

AT28C040-25FI is available at Aetrix Electronics and suitable for industrial PLCs, legacy PC motherboard designs, and medical device calibration systems requiring stable component supply and long-lifecycle support.

Supply support for AT28C040-25FI 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

Atmel Corporation (now part of Microchip Technology) is a semiconductor manufacturer specializing in microcontrollers, nonvolatile memory, and secure authentication ICs.

The AT28C040 product line delivers high-reliability parallel EEPROMs for legacy system upgrades and industrial applications where byte-level write granularity and deterministic timing are critical.

FAQ

What is the operating temperature range for the AT28C040-25FI?

The AT28C040-25FI is rated for industrial temperature operation from –40°C to +85°C. This specification is confirmed in the DC and AC Operating Range table of the official Atmel datasheet Rev. 0542B–10/98, and applies specifically to the FI suffix variant. The AT28C040-25FI meets this range without derating and supports reliable operation in harsh industrial environments where thermal cycling occurs.

Does the AT28C040-25FI support true byte-write operations?

Yes, the AT28C040-25FI supports both byte-write and page-write modes. In byte-write mode, a single byte is written per WE pulse, with automatic internal timing. The device latches address and data on the falling edge of CE or WE (whichever occurs last), then completes programming autonomously. This behavior is explicitly defined in the "Device Operation" section of the AT28C040 datasheet and is electrically identical across all speed grades including the AT28C040-25FI.

What does the "SL703" suffix in AT28C040-25FI SL703 indicate?

The "SL703" suffix denotes a specific traceability and screening level applied by Atmel, indicating lot-level documentation, extended testing, and compliance with additional quality assurance protocols beyond standard industrial grade. It appears in the Ordering Information table (page 10) as an optional suffix for FI, BI, and LI variants. The AT28C040-25FI SL703 retains all electrical and timing specifications of the base AT28C040-25FI while adding enhanced supply-chain visibility.

How is write completion detected on the AT28C040-25FI?

Write completion on the AT28C040-25FI is detected using two hardware-supported methods: DATA polling on I/O7 (which returns the complement of the last written byte until completion) and toggle-bit detection on I/O6 (which toggles between 0 and 1 during programming). Both mechanisms are active simultaneously and require no external timing components. These features are fully documented in the "Device Operation" section and apply identically to the AT28C040-25FI.

Is the AT28C040-25FI pin-compatible with older EPROMs like the 27C040?

No, the AT28C040-25FI is not pin-compatible with the 27C040 EPROM. While both are 4-Mbit parallel devices in 44-pin packages, the AT28C040-25FI uses JEDEC-standard byte-wide pinout with dedicated WE and OE controls, whereas the 27C040 uses OE/PGM pin sharing and lacks WE. Direct substitution would require PCB layout changes. However, the AT28C040-25FI *is* pin-compatible with other AT28C040 variants (e.g., AT28C040-25LI) in the same LCC-44 package.