Microchip Technology AT28BV256-20JU

Overview

AT28BV256-20JU from Atmel is a 256 Kbit (32K × 8) parallel EEPROM with JEDEC-standard byte-wide pinout, operating from a single 2.7V–3.6V supply, delivering 200 ns read access time and supporting 64-byte page writes in ≤10 ms. It features hardware/software data protection, Data Polling and Toggle Bit write completion detection, and is rated for industrial temperature (−40°C to +85°C) in a 32-lead PLCC package.

For engineers reviewing the AT28BV256-20JU datasheet, AT28BV256-20JU pinout, AT28BV256-20JU application, or AT28BV256-20JU equivalent, key selection criteria include its battery-voltage operation, CMOS standby current (≤50 µA), endurance (10,000 cycles), data retention (10 years), and compatibility with SRAM-like interface timing without external components.

Technical Context

The AT28BV256-20JU implements a static RAM-compatible parallel interface with dual-line chip enable (CE) and output enable (OE) control to prevent bus contention. Its internal 64-byte page register latches address and data during write operations, decoupling the bus for concurrent system activity.

Write execution uses an internal control timer after latch completion; end-of-write is confirmed via I/O7 Data Polling (complement-to-data toggle) or I/O6 Toggle Bit behavior. Software Data Protection requires a three-byte unlock sequence before any write, while hardware safeguards include VCC power-on delay, noise filtering on WE/CE, and write-inhibit logic.

Key Specifications

Pinout & Package

AT28BV256-20JU is housed in a 32-lead Plastic J-Leaded Chip Carrier (PLCC), JEDEC MS-016 compliant, with pins 1 and 17 designated as No Connect (NC). The package provides robust thermal performance and socket compatibility for prototyping and rework.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT28C256-15PU, the AT28BV256-20JU enables 3.3V-native operation and secure writes but trades 50 ns speed for robustness; versus M95256-DW, it delivers deterministic parallel timing and page efficiency at the cost of board area and interface complexity.

Availability

AT28BV256-20JU is available at Aetrix Electronics and suitable for industrial automation, medical instrumentation, automotive body electronics, and telecom infrastructure requiring stable component supply, long-lifecycle support, and green (Pb/halide-free) packaging.

Supply support for AT28BV256-20JU 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.

The AT28BV256 belongs to Atmel's battery-voltage parallel EEPROM product line, engineered for reliable, low-power, SRAM-drop-in replacement in legacy and new industrial systems requiring robust data retention without external voltage translation.

FAQ

What is the maximum page write size supported by the AT28BV256-20JU?

The AT28BV256-20JU supports a maximum page write size of 64 bytes. This is implemented via an internal 64-byte page register that latches addresses and data during a single write initiation. All bytes in a page write must reside on the same page, defined by A6–A14, and each successive byte must be loaded within 150 µs of the previous one to remain in page mode. The AT28BV256-20JU completes the entire 64-byte write in ≤10 ms using its internal control timer.

Does the AT28BV256-20JU require external circuitry for write protection?

No, the AT28BV256-20JU integrates both hardware and software write protection without external components. Hardware protection includes VCC power-on delay (~10 ms), noise filtering on WE/CE inputs (<15 ns pulse rejection), and multi-signal gating (CE/OE/WE). Software Data Protection requires a mandatory three-byte unlock sequence (5555H/2AAAH/5555H) before any write. The AT28BV256-20JU enforces these mechanisms autonomously-no external resistors, capacitors, or logic are needed.

How is write completion detected on the AT28BV256-20JU?

Write completion on the AT28BV256-20JU is detected using two independent methods: Data Polling on I/O7 and the Toggle Bit on I/O6. During a write, reading the last written byte returns the complement of the data on I/O7; when true data appears, the write is complete. Alternatively, I/O6 toggles between 0 and 1 during the write and stops toggling once finished. Both methods work at any time during the write cycle and require no additional pins or clocks-the AT28BV256-20JU handles all timing internally.

What is the purpose of the extra 64 bytes of EEPROM in the AT28BV256-20JU?

AT28BV256-20JU includes an additional 64 bytes of user-accessible EEPROM located at addresses 7FC0H–7FFFH, intended for device identification, calibration data, or manufacturing tracking. Access requires raising A9 to 12.0V ± 0.5V-this high-voltage enable prevents accidental writes during normal 3.3V operation. Once enabled, the extra memory behaves identically to main array reads/writes. This feature allows unique serialization or field-programmable configuration without consuming main memory space-critical for traceability in regulated industries.

Is the AT28BV256-20JU pin-compatible with standard SRAM devices?

The AT28BV256-20JU uses a JEDEC-approved byte-wide pinout identical to common 32K × 8 SRAMs (e.g., 62256), enabling direct PCB footprint reuse. Its CE, OE, and WE signals map functionally to standard SRAM control lines, and I/O0–I/O7 provide bidirectional 8-bit data transfer. However, write timing differs: the AT28BV256-20JU requires a write pulse followed by internal programming, whereas SRAM writes complete synchronously. Thus, while pinout and read behavior are compatible, firmware must accommodate the AT28BV256-20JU's write latency and completion detection.