Microchip Technology AT28C64X-15SI

Overview

AT28C64X-15SI from Atmel is a 64 Kbit (8K × 8) parallel EEPROM with JEDEC-standard byte-wide pinout, 150 ns read access time, 1 ms fast byte write cycle, and industrial temperature range (–40°C to +85°C). It operates from 5V ±10%, supports DATA polling and READY/BUSY signaling (RDY/BUSY pin unconnected in X variant), and is used for nonvolatile configuration storage in microcontroller-based systems requiring field-updatable firmware parameters.

For engineers reviewing the AT28C64X-15SI datasheet, AT28C64X-15SI pinout, AT28C64X-15SI application, or AT28C64X-15SI equivalent, key selection criteria include its self-timed write architecture, CMOS/TTL compatibility, 10⁴ endurance cycles, 10-year data retention, and industrial-grade reliability without external timing components.

Technical Context

The AT28C64X-15SI implements a self-timed byte write cycle with internal address/data latches and automatic clear-before-write logic, eliminating need for external write timing control. Its RDY/BUSY output is not connected (NC), relying exclusively on DATA polling via I/O7 complement detection to signal write completion.

It uses standard parallel memory interface timing: CE and OE control read enable with WE high; byte write initiates on falling WE edge with data latched on rising WE edge. VCC sense (3.8 V threshold) and 5 ms power-on delay prevent inadvertent writes during power ramp-up.

Key Specifications

Pinout & Package

AT28C64X-15SI is supplied in a 28-lead SOIC (28S) package per JEDEC MS-012, with 300-mil width and gull-wing leads. Pin 1 is NC (no connect); RDY/BUSY function is disabled per AT28C64X variant specification.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT28C64X-15SI, AT28C64B-15SI offers higher endurance and tighter AC specs for mission-critical updates, while MX28LV640E-15SI trades marginally higher reliability for lower standby current - both require no PCB changes but differ in write-cycle robustness and power sequencing behavior.

Availability

AT28C64X-15SI is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, automotive body electronics, and point-of-sale terminals requiring stable component supply across extended product lifecycles.

Supply support for AT28C64X-15SI 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 AT28C64X series was designed as a drop-in replacement for EPROM and early EEPROM solutions in 5 V embedded systems, emphasizing ease of integration, industrial reliability, and zero-external-component write timing.

FAQ

What is the RDY/BUSY functionality of the AT28C64X-15SI?

The AT28C64X-15SI has RDY/BUSY pin 1 designated as NC (no connect) per datasheet Rev. 0001H. Unlike base AT28C64 variants, this pin is internally unconnected and must remain floating. Write completion must be detected solely via DATA polling on I/O7 - reading the target location returns complemented data until the 1 ms write cycle completes, then returns true data.

Does the AT28C64X-15SI support chip erase, and how is it performed?

Yes, the AT28C64X-15SI supports chip erase. It requires applying 12.0 V ± 0.5 V to pin A9 while holding CE low and OE at 12 V, then issuing a 10 ms low pulse on WE. This operation sets all memory locations to 0xFF. The 12 V level must be externally generated and applied only during erase - normal operation uses only 5 V. The extra 32-byte ID area is unaffected by chip erase.

What is the endurance rating of the AT28C64X-15SI, and how is it validated?

The AT28C64X-15SI is rated for 10,000 write/erase cycles per memory location, verified per JEDEC JESD22-A117 stress testing methodology. This endurance applies across the full industrial temperature range (–40°C to +85°C) and accounts for worst-case voltage (5.5 V) and timing conditions. Endurance is not cumulative across addresses - each byte wears independently.

Can the AT28C64X-15SI be used with 3.3 V microcontrollers?

No, the AT28C64X-15SI is strictly a 5 V device: inputs require VIH ≥ 2.0 V and VIL ≤ 0.8 V, outputs drive to VOH ≥ 2.4 V at –400 µA, and VCC must be 5 V ±10%. Interfacing with 3.3 V logic requires level translation on all 13 address, 8 data, and 3 control lines - direct connection risks latch-up or undefined behavior due to input voltage exceeding 3.3 V logic high thresholds.

How does the AT28C64X-15SI handle power-up write protection?

The AT28C64X-15SI incorporates three-tiered write protection: (1) VCC sense disables writes below ~3.8 V; (2) internal 5 ms power-on delay after VCC reaches 3.8 V before write enable; and (3) hardware inhibition if CE is high, OE is low, or WE is high. These features ensure no unintended writes occur during brown-out, reset, or incomplete power ramp - critical for AT28C64X-15SI deployment in unattended industrial equipment.