Microchip Technology AT28C64E-20JI

Overview

AT28C64E-20JI from Atmel is a 64K-bit (8K × 8) parallel EEPROM with JEDEC-standard byte-wide pinout, 200 µs fast byte write time, 120 ns read access, and industrial temperature range (–40°C to +85°C). It operates on 5V ±10%, supports READY/BUSY and DATA polling for write cycle detection, and is used in firmware storage, configuration memory, and boot code retention in embedded controllers.

For engineers reviewing the AT28C64E-20JI datasheet, AT28C64E-20JI pinout, AT28C64E-20JI application, or AT28C64E-20JI equivalent, key selection criteria include write endurance (10⁵ cycles), CMOS standby current (100 µA), self-timed write architecture, and compatibility with microprocessor bus interfaces requiring nonvolatile byte-addressable storage without external timing components.

Technical Context

The AT28C64E-20JI implements a self-timed byte write cycle with internal address/data latches and an automatic clear-before-write sequence. Its RDY/BUSY open-drain output and I/O7 data polling provide two independent methods to detect write completion without halting the host processor.

It uses Atmel's proprietary nonvolatile technology with built-in error correction for enhanced data retention (10 years) and endurance (100,000 cycles). The device includes 32 bytes of dedicated identification EEPROM at addresses 1FE0H–1FFFH, accessible via A9 = 12 V, and supports chip erase using 12 V on OE with a 10 ms WE pulse.

Key Specifications

Pinout & Package

AT28C64E-20JI is packaged in a 32-lead Plastic J-Leaded Chip Carrier (PLCC), compliant with JEDEC MS-016AE. Pin 1 is index-marked; pins 1 and 17 are designated "Don't Connect" per datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT28C64B-20JI, the AT28C64E-20JI delivers 10× higher endurance and 5× faster writes, enabling frequent field updates; versus MN6264C-20J, it adds hardware-level RDY/BUSY signaling for deterministic timing-critical systems, at the cost of one additional board trace and pull-up resistor.

Availability

AT28C64E-20JI is available at Aetrix Electronics and suitable for industrial PLCs, legacy embedded boot systems, point-of-sale terminals, telecom line cards, and medical instrumentation requiring stable component supply across extended product lifecycles.

Supply support for AT28C64E-20JI 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 devices.

The AT28C64 family was designed as a drop-in parallel EEPROM replacement for UV-erasable EPROMs and battery-backed SRAMs in 8-bit and 16-bit microprocessor systems, emphasizing ease of integration, industrial reliability, and zero-external-component operation.

FAQ

What is the maximum write endurance specification for AT28C64E-20JI?

The AT28C64E-20JI is rated for 100,000 write/erase cycles - a 10× improvement over the standard AT28C64B variant. This endurance level is validated under industrial temperature conditions (–40°C to +85°C) and supports applications requiring regular firmware or configuration updates. Each cycle represents a full byte write and erase at any address location within the 8K × 8 memory array. The AT28C64E-20JI achieves this via enhanced oxide quality and internal error correction logic.

Does AT28C64E-20JI support both hardware and software methods to detect write completion?

Yes, AT28C64E-20JI provides dual write-completion detection: RDY/BUSY (pin 1) outputs an active-low open-drain signal during writes, and DATA polling monitors I/O7 - which toggles to the complement of written data until completion. These methods operate independently and can be used simultaneously. The AT28C64E-20JI datasheet specifies tDB ≤ 50 ns for RDY/BUSY assertion and guarantees deterministic polling behavior, making it suitable for both interrupt-driven and polling-based host firmware.

What is the function of the 32-byte ID memory block in AT28C64E-20JI?

The AT28C64E-20JI includes 32 bytes of user-accessible EEPROM at addresses 1FE0H–1FFFH, enabled by applying 12 V ±0.5 V to A9. This block functions as a dedicated serialization area for storing unique identifiers, calibration constants, manufacturing dates, or firmware version stamps. Unlike main memory, it is electrically isolated and retains data independently. Access follows the same timing as main array reads/writes, and the AT28C64E-20JI supports full read/write/erase operations on this region using standard CE/OE/WE controls once A9 voltage is asserted.

Can AT28C64E-20JI be used as a direct replacement for older EPROMs like 27C64?

No - AT28C64E-20JI is not a pin-compatible or functional replacement for 27C64 EPROMs. While both are 64K-bit parallel memories, the AT28C64E-20JI requires active WE control and supports in-system electrical erasure, whereas 27C64 needs UV erasure and lacks write-enable logic. However, AT28C64E-20JI can replace 27C64 in new designs where board layout accommodates its JEDEC-standard pinout and microprocessor-controlled write sequencing. Its 200 ns read access and 5 V operation simplify migration from 27C64-200 variants.

What write protection mechanisms does AT28C64E-20JI implement to prevent accidental writes?

The AT28C64E-20JI implements three layered write protections: (1) VCC sense - disables writes if supply drops below ~3.8 V; (2) 5 ms power-on delay - prevents writes until VCC stabilizes; and (3) triple-gated inhibit - requires simultaneous violation of CE high, OE low, or WE high to block writes. These features are inherent to the AT28C64E-20JI silicon design and require no external components. They ensure immunity to noise-induced glitches, brownouts, and improper power sequencing - critical for unattended industrial deployments of AT28C64E-20JI.