Microchip Technology AT28C040-20FC

Overview

AT28C040-20FC from Atmel is a 4-Mbit (512K × 8) paged parallel EEPROM with 200 ns read access time, JEDEC byte-wide pinout, and single 5V ±10% supply. It supports automatic page write of up to 256 bytes with internal latching and timer control, and is used in firmware storage, configuration memory, and boot code retention for industrial controllers and telecom line cards.

For engineers reviewing the AT28C040-20FC datasheet, AT28C040-20FC pinout, AT28C040-20FC application, or AT28C040-20FC equivalent, key selection criteria include page write timing (≤10 ms), DATA polling/Toggle Bit write completion detection, hardware/software data protection, and LCC-44 ceramic package compatibility with high-reliability embedded systems.

Technical Context

The AT28C040-20FC implements a CMOS-based paged EEPROM architecture with 256-byte page register, enabling burst writes without external address/data bus hold. Its dual-line chip enable (CE) and output enable (OE) control allows static RAM–like read access while preventing bus contention during standby.

Write operation relies on internal control timer and supports three detection methods: DATA polling on I/O7, Toggle Bit on I/O6, and software command sequencing. 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

Ceramic Leadless Chip Carrier (LCC), 44-pad, non-windowed, JEDEC MO-115 / MIL-STD-1835 C-5 compliant package with side-braze construction and flat top surface. Pin 1 identified by corner cut and dot marking; no internal lid venting required.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ST M48T02-200PC1 and Microchip 25LC1024-I/P, the AT28C040-20FC delivers 4× higher density, JEDEC-standard parallel interface for legacy system upgrades, and deterministic 200 ns read timing-making it the only viable option for retrofitting existing 44-LCC footprint designs requiring >512 Kbyte nonvolatile storage.

Availability

AT28C040-20FC is available at Aetrix Electronics and suitable for industrial PLC configuration storage, telecom line card boot memory, and medical diagnostic equipment calibration requiring stable component supply and long-lifecycle support.

Supply support for AT28C040-20FC 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 fabless semiconductor company specializing in microcontrollers, nonvolatile memory, and secure authentication ICs for industrial, automotive, and consumer applications.

The AT28C040 product line was designed for high-reliability, pin-compatible replacement of battery-backed SRAM and earlier-generation EEPROMs in mission-critical embedded systems requiring field-upgradable firmware and configuration data.

FAQ

What is the maximum page write size supported by the AT28C040-20FC?

The AT28C040-20FC supports page write operations of 1 to 256 bytes per internal programming cycle. All bytes written in a single page operation must reside within the same 256-byte page boundary defined by address bits A8–A18. The AT28C040-20FC uses an internal 256-byte latch and timer to execute the entire page write autonomously after the first byte is latched.

Does the AT28C040-20FC require a high-voltage programming supply?

No, the AT28C040-20FC operates from a single 5V ±10% supply and contains an integrated charge pump for internal high-voltage generation during write/erase cycles. No external VPP or 12V supply is needed. However, the optional device identification area (7FF80H–7FFFFH) does require A9 raised to 12V ±0.5V for access-this is strictly for ID memory and not for normal operation of the AT28C040-20FC.

How is write completion detected on the AT28C040-20FC?

The AT28C040-20FC provides two hardware-supported methods: DATA polling on I/O7 (complement of last written byte appears until write completes) and Toggle Bit on I/O6 (toggles between 0 and 1 during write, then stabilizes). Both methods allow polling without fixed timeouts. The AT28C040-20FC does not require external READY/BUSY signals or status registers.

Is the AT28C040-20FC pin-compatible with standard SRAM devices?

Yes-the AT28C040-20FC uses a JEDEC-approved byte-wide pinout identical to common 512K × 8 SRAMs (e.g., AS6C8008, CY62187) in the 44-LCC package. Address, data, CE, OE, and WE signals align directly, enabling drop-in replacement in many designs-though timing differences (e.g., write cycle duration, no write enable during reads) must be verified in the target system's AT28C040-20FC implementation.

What protection mechanisms prevent accidental writes to the AT28C040-20FC?

The AT28C040-20FC includes hardware protection (VCC sense disabling writes below ~3.8 V, 5 ms power-on delay, noise filtering on WE/CE, and CE/OE/WE logic inhibition) and optional software data protection (SDP) activated via a 3-byte command sequence. Once enabled, SDP requires the same sequence before each write-even for page operations. These protections are active across power cycles and apply uniformly to all memory locations in the AT28C040-20FC.