Microchip Technology AT28BV256-20SI

Overview

AT28BV256-20SI from Atmel is a 256 Kbit (32K × 8) parallel EEPROM operating from a single 2.7V–3.6V supply, featuring 200 ns read access time, 10 ms maximum page write cycle, JEDEC-standard byte-wide pinout, and industrial temperature range (−40°C to +85°C). It supports hardware/software data protection and DATA polling for write completion detection in embedded control and firmware storage applications.

For engineers reviewing the AT28BV256-20SI datasheet, AT28BV256-20SI pinout, AT28BV256-20SI application, or AT28BV256-20SI equivalent, key selection criteria include its 200 ns read timing, 64-byte page write capability, CMOS standby current of 20 µA, industrial-grade reliability (10,000 write cycles, 10-year data retention), and compatibility with standard SRAM-like bus interfacing.

Technical Context

The AT28BV256-20SI implements a parallel interface with CE/OE/WE control logic enabling SRAM-compatible read/write operations without external timing components. Its internal 64-byte page register latches address and data during page writes, decoupling the host bus while an internal timer executes programming.

Write completion is verified via DATA polling on I/O7 (complement-to-data toggle) or TOGGLE BIT behavior on I/O6, both usable at any point during the write cycle. Hardware protection includes VCC power-on delay (~10 ms), noise filtering (<15 ns pulse rejection), and write inhibit via OE high, CE high, or WE high states.

Key Specifications

Pinout & Package

AT28BV256-20SI is supplied in a 28-lead SOIC (28S) package per JEDEC MS-013, with 300-mil body width and gull-wing leads. Pin 1 is marked by a beveled corner or notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT28BV256-20SI, AT28C256-20PI mandates 5V operation limiting use in modern low-voltage systems, while ST M28W256FBD-20N6 omits the user-accessible ID memory and uses divergent software protection-making AT28BV256-20SI preferable for designs needing battery-voltage support, embedded device tracking, or Atmel toolchain compatibility.

Availability

AT28BV256-20SI is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, automotive ECUs, and networking equipment requiring stable component supply across extended product lifecycles.

Supply support for AT28BV256-20SI 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 security ICs for embedded applications.

The AT28BV256 product line delivers battery-voltage parallel EEPROMs optimized for firmware storage, configuration retention, and calibration data logging in industrial, automotive, and medical systems demanding high reliability and low-power operation.

FAQ

What is the operating voltage range of the AT28BV256-20SI?

The AT28BV256-20SI operates from a single 2.7V to 3.6V supply, making it suitable for 3.3V logic systems and battery-backed applications. This voltage range enables compatibility with modern low-power microcontrollers and eliminates the need for level-shifting circuitry in mixed-voltage designs. The AT28BV256-20SI incorporates internal VCC monitoring to enforce hardware write protection until the supply stabilizes above 1.8V.

How does the AT28BV256-20SI handle write completion detection?

The AT28BV256-20SI provides two hardware-supported methods: DATA polling on I/O7 (returns complement of written data until complete) and TOGGLE BIT on I/O6 (toggles between 0 and 1 during write). Both methods allow the host processor to detect completion using standard read cycles without timers or interrupts. This functionality is fully implemented in the AT28BV256-20SI and requires no external components.

Does the AT28BV256-20SI support page writing, and what is the maximum size?

Yes, the AT28BV256-20SI supports page writing of 1 to 64 bytes within a single internal programming cycle, with a maximum page write time of 10 ms. All bytes must reside on the same page (defined by A6–A14), and successive bytes must be loaded within 150 µs. This capability significantly accelerates firmware updates compared to byte-by-byte writes and is a core feature of the AT28BV256-20SI architecture.

What is the purpose of the extra 64-byte memory area in the AT28BV256-20SI?

The AT28BV256-20SI includes an additional 64-byte EEPROM block accessible at addresses 7FC0H–7FFFH, activated by raising A9 to 12V ± 0.5V. This area is intended for device-specific data such as serial numbers, calibration constants, manufacturing dates, or firmware version stamps. Unlike main array writes, this region uses the same software protection and timing as the primary memory, ensuring consistent reliability in the AT28BV256-20SI.

Is the AT28BV256-20SI pin-compatible with standard EPROMs or other EEPROMs?

The AT28BV256-20SI uses a JEDEC-approved byte-wide pinout identical to industry-standard 27C256 EPROMs and many parallel EEPROMs, enabling direct PCB footprint reuse. Its 28-pin SOIC (28S) package matches common socket layouts. However, voltage and timing differences-especially the 2.7V–3.6V operation versus 5V EPROMs-require verification of host interface compatibility before substitution in existing designs using the AT28BV256-20SI.