Microchip Technology AT28C64B-15PU

Introduction to the AT28C64B-15PU EEPROM by Microchip Technology

The AT28C64B-15PU from Microchip Technology is a high-performance, parallel-interface EEPROM (Electrically-Eraseable Programmable Read-Only Memory) that delivers 64K bits of non-volatile memory, organized as 8,192 words by 8 bits. Built on robust CMOS technology, the device is designed for demanding industrial and embedded applications where quick access times, reliable data integrity, and robust data protection are required. Its compatibility with both CMOS and TTL logic levels, JEDEC-standard pinout, and operation over the industrial temperature range (-40°C to 85°C) make it an attractive solution for system design and product lifecycle considerations.

Main Attributes and Technical Benefits of the AT28C64B-15PU

The AT28C64B-15PU distinguishes itself with a blend of speed, power efficiency, and user-friendly features. It achieves a fast read access time of 150 ns, enabling rapid memory fetches in time-critical systems. Its internal 64-byte page register allows for page write operations (up to 64 bytes at a time), optimizing write performance: the page write cycle time is typically 10 ms (with faster options available in related product variants). Active current consumption is a modest 40 mA, with standby current under 100 μA in CMOS mode, promoting energy efficiency in always-on or battery-critical applications.

The device incorporates advanced reliability features, including hardware and software data protection, built-in error correction, a rated endurance of 100,000 write/erase cycles, and a data retention period of at least 10 years. For system compatibility, the AT28C64B-15PU operates on a single 5V ±10% supply.

Pin Layout and Available Packages for AT28C64B-15PU

The AT28C64B-15PU is offered in through-hole 28-pin PDIP (Dual Inline Package), a familiar and robust package ideal for prototyping, socketed applications, and products where soldering and rework flexibility are needed. The JEDEC-compliant pinout enables straightforward socketing and board placement, while supporting parallel access to all address and data lines. This parallel interface simplifies direct memory mapping into microprocessor or microcontroller address spaces.

All address (A0–A12), data (I/O0–I/O7), and key control pins (CE, OE, WE) are clearly arranged for ease of routing, with additional pins for device identification and test functions. Alternate package options (beyond "PU" suffix) may include SOIC, PLCC, or TSOP, offering increased flexibility for automated surface mount assembly or constrained footprints.

Device Functions Reading, Writing, and Data Handling in AT28C64B-15PU

The AT28C64B-15PU is designed for SRAM-like operation, meaning reads and writes occur via direct parallel access without the need for external program/erase voltages or complex protocols. For read operations, when both Chip Enable (CE) and Output Enable (OE) are asserted low (and Write Enable, WE, is high), data from the selected address appears at the outputs, with high-impedance output mode provided when these conditions are not met to facilitate bus sharing.

Write operations are supported by both byte and page modes. A single byte can be written by pulsing WE or CE with appropriate signal timing. For more efficient write throughput, page write mode supports 1–64 bytes written in a single cycle, with data and addresses latched internally—a boon in applications needing frequent bulk updates.

The AT28C64B-15PU also supports end-of-write detection via two methods: DATA Polling (I/O7 indicates operation complete by matching written data) and toggle bit (I/O6 toggles during programming and stops when ready). These features support efficient polling strategies for CPU-driven or DMA-driven memory programming.

Built-in Data Security Features of the AT28C64B-15PU

Reliability in memory programming is further enhanced through multiple layers of data protection. Hardware mechanisms include voltage sensing (write is inhibited if Vcc < 3.8V), power-on delays before write enablement, logic state-based write inhibit (preventing writes when certain control signals are in protective states), and input noise filtering to reject spurious write triggers.

Software Data Protection (SDP) offers another level, enabling users to activate or deactivate in-field write protection by issuing a secure, three-byte command sequence. With SDP enabled, all subsequent write operations require the same three-byte precursor, enhancing security against accidental or spurious writes in complex system environments or during power transitions. SDP states persist through any power cycle, further safeguarding application data.

The AT28C64B-15PU also provides an extra 64 bytes of EEPROM memory specifically for device identification or tracking, accessible via an elevated A9 pin voltage and dedicated address space.

Electrical Specifications and Performance of AT28C64B-15PU

The AT28C64B-15PU supports a supply voltage from 4.5V to 5.5V, offering flexibility with legacy and modern 5V systems. It is characterized for full industrial temperature operation (-40°C to 85°C). Critical timing specifications include:

Address to output delay (read access time): 150 ns max

Page write cycle time: 10 ms max (typical configuration)

Maximum active current: 40 mA at 5 MHz operation

CMOS standby current: 100 μA max

These attributes ensure suitability for timing-critical and energy-constrained designs, including PLCs, instrumentation, and industrial controllers.

Package Details and Environmental Standards for AT28C64B-15PU

The AT28C64B-15PU is supplied in a 28-pin dual in-line (PDIP) package with a 0.600" (15.24mm) width, facilitating straightforward hand or automation-based insertion into standard boards. The device is RoHS3-compliant and halide-free, supporting eco-friendly manufacturing practices. Moisture Sensitivity Level (MSL) is rated at 1 (unlimited), and the device is REACH unaffected, ensuring minimal supply chain and handling restrictions for global procurement. Absolute maximum ratings allow for storage from –65°C to +150°C, and input tolerance up to +6.25V (non-operational conditions).

Alternative or Substitute Models for the AT28C64B-15PU

Product selection engineers and procurement professionals should note that the AT28C64B-15PU represents a widely adopted pin-for-pin replacement for legacy 64Kb parallel EEPROMs. Alternate models in the Microchip/Atmel lineup include faster page write variants such as the AT28HC64BF. Additionally, devices such as the AT28C64-15PU (without the “B” suffix), or industry-compatible models from other major EEPROM providers, may serve as direct or near-equivalent replacements, provided their timing, supply voltage, and protection features match the system requirements. Surface-mount packages (e.g., AT28C64B-15SI SOIC) may also be explored for PCB space constraints, ensuring that the core specifications match the design needs of the target application.

Conclusion

The AT28C64B-15PU EEPROM from Microchip Technology is a robust, time-tested solution for non-volatile memory needs in parallel-access architectures. With its high speed, low power, advanced data protection mechanisms, and industrial-grade reliability, it remains an optimal choice for designs where data integrity and operational durability are paramount. Its multiple protection layers, flexible write modes, available identification memory, and broad package options facilitate both today’s and tomorrow’s embedded system requirements, making it a standout candidate for engineers and procurement teams focused on long-term product support and performance.