Microchip Technology AT28C64B-15JU

AT28C64B-15JU Parallel EEPROM Product Summary

The Microchip Technology AT28C64B-15JU is a 64Kbit parallel EEPROM designed for applications requiring fast access times and high reliability. Packaged in a 32-pin PLCC, the AT28C64B-15JU offers 8K x 8 organization, with the full advantage of being electrically erasable and programmable. Its advanced CMOS technology not only ensures robust retention and endurance but also achieves low-power operation suitable for demanding engineering environments. Qualified for industrial temperature ranges and JEDEC-compliant, this device is an ideal candidate for system designs where nonvolatile memory and rapid parallel data transfer are essential.

Main Attributes and Performance Metrics of AT28C64B-15JU

Engineers evaluating the AT28C64B-15JU will find several standout specifications:

Fast read access time of 150ns, enabling high-speed data retrieval.

Flexible memory organization, supporting byte-wide and page write operations (up to 64 bytes per write).

Efficient write cycle times: 10ms maximum for page writes, with an optional 2ms fast mode (referenced from AT28HC64BF).

Low power dissipation: 40mA active current and only 100μA CMOS standby current.

Hardware and software data protection features safeguard data integrity during system power events and against inadvertent writes.

Robust endurance of 100,000 programming cycles and data retention exceeding 10 years.

Single 5V ±10% supply voltage.

CMOS and TTL compatible inputs and outputs enhance compatibility with a broad range of digital systems.

Green (Pb/Halide-free) package options for compliant assembly.

These capabilities make the AT28C64B-15JU well-suited for industrial control, telecommunications, and instrumentation platforms where performance and reliability are uncompromising requirements.

Functional Design and Working Principles of AT28C64B-15JU

The core functioning of the AT28C64B-15JU mirrors that of static RAM in both read and write cycles, promoting straightforward integration. On reads, the data at the addressed location is presented at the outputs when both chip enable (CE) and output enable (OE) are low, and write enable (WE) remains high. Output enters a high-impedance state if either CE or OE is high, easing system bus contention.

For writes, the AT28C64B-15JU incorporates internal address and data latches, supporting single-byte and 1–64 byte page write operations. This page write mechanism enables the simultaneous programming of up to 64 bytes, optimizing throughput and freeing the system bus during internal write cycles. Importantly, all data bytes in a page must reside within a single address page (A6–A12), and load timing must be managed to avoid incomplete transfers.

The device further supports write progress detection via DATA Polling (using I/O7) and the Toggle Bit feature (using I/O6), allowing real-time monitoring of internal programming status. Access to a reserved 64-byte device identification area is possible by applying a high voltage (12V) to A9, a convenient option for asset tracking and inventory management.

Data Security Features in AT28C64B-15JU

Recognizing the vulnerability of nonvolatile memory during system power transitions or noise events, the AT28C64B-15JU offers comprehensive data protection:

Hardware data protection includes a supply voltage sense circuit that disables programming below 3.8V, power-on write delay, write-inhibit functions via control pin states, and input noise filtering to reject short pulses on CE/WE.

Software Data Protection (SDP) is user-programmable and employs a specific three-byte command sequence to enable or disable protection. When activated, SDP reliably prevents unintended writes, even through power-cycle events, and can be selectively bypassed for authorized programming via command sequence.

These essential safeguards should be incorporated into system-level design to maintain information integrity, especially in environments with unstable or noisy power supplies.

Package Types and Pin Layouts for AT28C64B-15JU

AT28C64B-15JU is primarily available in a standard 32-lead PLCC configuration with JEDEC MS-016, Variation AE compliance. This package offers compact dimensions (13.97 x 11.43 mm) and robust lead coplanarity suitable for automated assembly. Other packaging formats in the AT28C64B series include PDIP, SOIC, and TSOP, providing flexibility for different system layouts and mounting requirements. Engineers should reference the JEDEC specifications for detailed pin mapping when designing PCB footprints, noting that some package positions are assigned as “No Connect” for optimal compatibility.

Electrical Specifications and Environmental Requirements of AT28C64B-15JU

The AT28C64B-15JU supports an industrial temperature operating range (-55°C to +125°C under bias), with storage capability up to +150°C. Absolute maximum voltages for inputs and outputs are ±0.6V around ground and up to 6.25V for inputs, ensuring resilience in harsh electrical environments. For device identification and some special functions, A9 can tolerate up to 13.5V. Active supply current during operation is 40mA, while standby draws less than 100μA.

Standard DC and AC parameters meet typical nonvolatile memory benchmarks, with fast read and write transition timings and tolerance for address/data transitions exceeding 1MHz. Timing diagrams and electrical response graphs are available in the full datasheet to assist engineers with detailed timing and system integration planning.

Alternative and Substitute Models for AT28C64B-15JU

When considering cross-platform implementations or lifecycle management, engineers may look to these alternatives within the Microchip Technology/Atmel portfolio and the broader EEPROM market:

AT28C64B series in alternate packages (PDIP, SOIC, TSOP) for different mounting requirements.

AT28HC64BF series, which offers faster write cycle times and similar parallel memory organization.

Other manufacturers’ 64Kbit parallel EEPROMs with compatible access timings, pinouts, and operating voltages, subject to verification of timing specifications, reliability metrics, and data protection features.

Before selecting a replacement, compatibility in terms of operational voltage, timing, and protection mechanisms should be evaluated, especially for legacy system upgrades or multi-sourcing strategies.

Conclusion

The AT28C64B-15JU stands out as a high-performance, reliable parallel EEPROM solution for engineering teams demanding fast access, robust endurance, and flexible integration. Its feature set—spanning fast access, high data protection, and diverse packaging choices—makes it ideal for industrial, instrumentation, and embedded designs. Careful analysis of its functional and electrical attributes, as well as consideration of direct replacements or upgrades, will ensure engineers and procurement teams make sound choices in sourcing and designing with the AT28C64B-15JU.