Microchip Technology AT28HC256-12JU-070

Overview

AT28HC256-12JU-070 from Microchip Technology is a 256-Kbit (32,768 × 8) parallel EEPROM IC used for nonvolatile program/data storage in embedded control and industrial systems. It delivers 70 ns read access time, supports 1–64-byte page writes with ≤10 ms internal write cycle, operates on single 5V ±10% supply, and features hardware/software data protection for reliable operation in -40°C to +85°C industrial environments.

For engineers reviewing the AT28HC256-12JU-070 datasheet, AT28HC256-12JU-070 pinout, AT28HC256-12JU-070 application, or AT28HC256-12JU-070 equivalent, key selection criteria include JEDEC byte-wide pin compatibility, DATA Polling/Toggle Bit write completion detection, 10,000/100,000 endurance cycles, industrial temperature rating, and PLCC-32 packaging with RoHS-compliant green finish.

Technical Context

The AT28HC256-12JU-070 implements a CMOS-based parallel EEPROM architecture with internal 64-byte page latches and autonomous write timing. Its dual-line chip enable (CE) and output enable (OE) logic enables bus contention avoidance, while VCC sense and 5 ms power-on delay prevent inadvertent writes during supply ramp-up.

Write operations support both byte and page modes, with tBLC ≤150 µs enforcing sequential byte loading within a page. End-of-write detection is implemented via I/O7 DATA Polling (complement-to-data response) and I/O6 Toggle Bit behavior-both accessible without external polling hardware.

Key Specifications

Pinout & Package

AT28HC256-12JU-070 uses a 32-lead Plastic Leaded Chip Carrier (PLCC) package with JEDEC-standard byte-wide pinout. Pins 1 and 17 are designated "Don't Connect" (DC); pins 12 and 26 are No Connect (NC). All address (A0–A14), data (I/O0–I/O7), and control (CE, OE, WE, VCC, GND) signals follow industry-standard memory mapping.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT28HC256-12JU-070, the AT28HC256-12PU offers identical functionality in a smaller SOIC package but forfeits PLCC advantages like socket compatibility and thermal dissipation; the ST M28W256FCT trades off advanced data protection for marginally faster writes and broader supply tolerance.

Availability

AT28HC256-12JU-070 is available at Aetrix Electronics and suitable for industrial PLCs, medical calibration systems, telecom line cards, and automotive body control modules requiring stable component supply across extended product lifecycles.

Supply support for AT28HC256-12JU-070 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 is a global semiconductor company specializing in microcontrollers, analog devices, and nonvolatile memory solutions, with a focus on reliability, longevity, and industrial-grade qualification.

The AT28HC256 product line delivers high-speed, pin-compatible EEPROMs designed for legacy system upgrades and new industrial designs requiring robust, low-power, parallel-interface nonvolatile storage.

FAQ

What does the "-12JU-070" suffix indicate in AT28HC256-12JU-070?

The "-12JU-070" suffix identifies the AT28HC256-12JU-070 as a 120 ns access time grade (12), packaged in a 32-lead PLCC (JU), with 70 ns actual read performance (070). This reflects Microchip's dual-speed binning: the "12" denotes the speed grade under worst-case conditions, while "070" confirms measured 70 ns access in characterization. The JU package is RoHS-compliant and rated for industrial temperature operation.

Does AT28HC256-12JU-070 support true random-access writes like SRAM?

No, AT28HC256-12JU-070 does not support true random-access writes. It requires explicit write enable (WE) and chip enable (CE) control, with internal write timing (up to 10 ms). While reads are SRAM-like, writes involve latching, internal programming, and end-of-write detection via DATA Polling or Toggle Bit. This differs fundamentally from volatile SRAM but maintains compatible bus protocol for seamless integration.

How is write protection implemented on AT28HC256-12JU-070?

AT28HC256-12JU-070 implements dual-layer write protection: hardware-level VCC sensing (inhibits writes below ~3.8 V), power-on delay (~5 ms), and noise filtering (<15 ns pulses ignored); plus software-level protection via a three-byte unlock sequence (AAh → 55h → A0h to enable, AAh → 55h → 80h → AAh → 20h → 55h to disable). Both layers operate independently and persist through power cycles.

Can AT28HC256-12JU-070 be used as a direct replacement for 27C256 EPROMs?

Yes, AT28HC256-12JU-070 is a functional and pin-compatible replacement for 27C256 EPROMs in most designs. It shares the same JEDEC byte-wide pinout, 32-pin PLCC package, and 32,768 × 8 organization. Unlike EPROMs, it requires no UV erasure and supports in-system electrical reprogramming - eliminating the need for EPROM programmers and UV erasers in production and field service.

What is the purpose of the 64-byte identification area in AT28HC256-12JU-070?

The 64-byte identification area (addresses 7FC0h–7FFFh) in AT28HC256-12JU-070 is a dedicated EEPROM segment accessible only when A9 is raised to 12V ±0.5V. It enables permanent, tamper-resistant storage of unique device identifiers, calibration constants, manufacturing date codes, or regulatory compliance data - separate from main memory and immune to standard 5V write operations.