Microchip Technology AT28C64-12SC

Overview

AT28C64-12SC from Atmel is a 64 Kbit (8K × 8) parallel EEPROM with 120 ns read access time, self-timed byte write (1 ms), CMOS/TTL-compatible I/O, and JEDEC-standard 28-pin SOIC package. It operates at 5V ±10%, supports commercial temperature range (0°C to 70°C), and delivers 30 mA active current and 100 µA standby current for embedded microcontroller systems requiring nonvolatile configuration storage.

For engineers reviewing the AT28C64-12SC datasheet, AT28C64-12SC pinout, AT28C64-12SC application, or AT28C64-12SC equivalent, this page provides verified technical context, JEDEC-compliant pin mapping, endurance and timing specifications, ready/busy signaling behavior, and validated alternative parts for legacy system maintenance and BOM continuity planning.

Technical Context

The AT28C64-12SC implements a parallel EEPROM architecture with internal address/data latching and an autonomous control timer that manages erase-before-write sequencing without external timing components. Its RDY/BUSY open-drain output and DATA polling on I/O7 provide two independent methods to detect write completion.

It features VCC sense (write inhibit below 3.8 V), 5 ms power-on delay before write enable, and triple-level write protection via CE/OE/WE logic states. The device includes 32 bytes of dedicated identification memory accessible at 1FE0H–1FFFH using A9 = 12 V, and supports chip clear via OE = 12 V and WE pulse.

Key Specifications

Pinout & Package

AT28C64-12SC is housed in a 28-lead, 0.300" wide plastic gull-wing small outline (SOIC) package per JEDEC MS-012AB, with pin 1 marked by index notch and pin 1 located at top-left corner when viewed from top with marking side up.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT28C64-12SC, AT28C64B-12SC offers superior longevity and lower leakage, while MX28LV640C-12SC maintains mechanical and timing equivalence but shifts write safety responsibility to system-level voltage supervision - making each choice dependent on whether reliability extension or footprint fidelity is the primary constraint.

Availability

AT28C64-12SC is available at Aetrix Electronics and suitable for industrial PLCs, legacy PC BIOS modules, medical calibration systems, and point-of-sale terminals requiring stable component supply and long-term obsolescence management.

Supply support for AT28C64-12SC 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 ICs for industrial, automotive, and consumer applications.

The AT28C64 product line was designed as a drop-in parallel EEPROM replacement for battery-backed SRAM in 8-bit and 16-bit embedded systems, emphasizing ease of integration, JEDEC compliance, and robustness in unattended operation.

FAQ

What is the maximum operating temperature range for the AT28C64-12SC?

The AT28C64-12SC is rated for commercial temperature operation from 0°C to 70°C. This is explicitly defined in the ordering information table, where the "SC" suffix denotes SOIC packaging with commercial-grade thermal specification. Industrial variants (e.g., AT28C64-12SI) extend to –40°C to +85°C, but AT28C64-12SC does not support that range.

Does the AT28C64-12SC support both RDY/BUSY and DATA Polling for write completion detection?

Yes, the AT28C64-12SC supports both methods. RDY/BUSY (pin 1) is an open-drain output pulled low during write and released upon completion. DATA Polling uses I/O7, which returns the complement of written data until the write finishes, then outputs true data. Both mechanisms are fully functional in the AT28C64-12SC per its datasheet AC and DC characteristics.

Can the AT28C64-12SC be used as a direct replacement for standard SRAM in a microprocessor system?

The AT28C64-12SC can replace SRAM for read operations due to identical read timing and pinout, but write behavior differs: it requires self-timed write cycles (1 ms) and status monitoring. Unlike SRAM, it cannot accept back-to-back writes without checking RDY/BUSY or polling I/O7. So while read interface is drop-in, write control logic must be adapted for nonvolatile timing.

What is the purpose of the 32-byte identification memory in the AT28C64-12SC?

The AT28C64-12SC includes 32 bytes of user-accessible EEPROM at addresses 1FE0H–1FFFH, enabled by applying 12 V ±0.5 V to A9. This area is intended for device-specific data such as serial numbers, calibration constants, manufacturing date codes, or firmware revision tags - separate from main memory and preserved across normal read/write operations.

How does write protection work on the AT28C64-12SC?

AT28C64-12SC implements three-tier write protection: (1) VCC sense disables writes if supply drops below ~3.8 V; (2) a 5 ms internal delay after VCC stabilization prevents premature writes during power-up; and (3) logical inhibition - holding CE high, OE low, or WE high blocks all byte write attempts. These features collectively prevent accidental corruption during brown-out or noise events.