AT28C64X-25PC Equivalent & Substitute Parts

Part Overview

The AT28C64X-25PC is a 64Kbit parallel EEPROM memory IC manufactured by Microchip Technology, housed in a 28-DIP package with 250 ns access time. This part is classified as obsolete, which necessitates identification of functionally compatible alternatives for ongoing system support and new designs. The obsolete status makes substitute parts essential for procurement and long-term product availability.

Substiute Parts

AT28C64X-25PC

Microchip TechnologyIn Stock: 902AT28C64X-25PC Datasheet

Current PartRFQ

AT28C64B-15PU

Microchip TechnologyIn Stock: 3411AT28C64B-15PU Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the AT28C64X-25PC is determined by the following critical parameters:

• Memory Capacity & Organization: Must maintain 64Kbit capacity with 8K x 8 organization to ensure address and data bus compatibility
• Memory Type & Format: Must be EEPROM with parallel interface to preserve circuit-level functionality
• Package & Pinout: Must use 28-DIP package with identical physical dimensions (0.600", 15.24mm) for PCB compatibility
• Voltage Supply Range: Must support 4.5V ~ 5.5V operation to match system power requirements
• Access Time: Substitute parts with equal or faster access time (≤250 ns) maintain or improve system timing margins
• Write Cycle Time: Substitute parts with equal or faster write cycle time maintain or improve programming speed

The AT28C64B-15PU meets all substitution criteria while offering improved electrical characteristics and active product status.

Parameter Comparison

Engineering Selection Recommendations

The AT28C64B-15PU is the direct substitute for the AT28C64X-25PC based on the following factors:

• Product Status: The AT28C64B-15PU holds active product status, ensuring long-term availability and supply chain continuity compared to the obsolete AT28C64X-25PC
• Regulatory Compliance: The AT28C64B-15PU is ROHS3 compliant, meeting current environmental and regulatory requirements, whereas the original part is RoHS non-compliant
• Electrical Compatibility: Both parts operate within the identical 4.5V ~ 5.5V supply range and maintain the same memory capacity, organization, and parallel interface
• Physical Compatibility: Identical 28-DIP package ensures direct PCB replacement without layout modifications
• Performance Characteristics: The AT28C64B-15PU provides faster read access time (150 ns vs. 250 ns), which improves system timing margins. The extended operating temperature range (-40°C ~ 85°C vs. 0°C ~ 70°C) supports broader application environments

Frequently Asked Questions (FAQ)

Q: Can the AT28C64B-15PU directly replace the AT28C64X-25PC on existing PCBs?

A: Yes. Both parts use the 28-DIP package with identical pinout and physical dimensions. No PCB modifications are required for direct substitution.

Q: What are the key differences between these parts?

A: The AT28C64B-15PU offers faster read access time (150 ns vs. 250 ns), a wider operating temperature range (-40°C ~ 85°C vs. 0°C ~ 70°C), and ROHS3 compliance. The write cycle time is longer (10 ms vs. 1 ms), which may affect programming speed in applications with frequent write operations.

Q: Are the supply voltages compatible?

A: Yes. Both parts operate within the 4.5V ~ 5.5V range, ensuring compatibility with existing power supply designs.

Q: Does the faster access time of the AT28C64B-15PU affect system compatibility?

A: No. Faster access time improves timing margins and is backward compatible with designs specified for the original 250 ns part.

Q: What is the significance of the RoHS compliance difference?

A: The AT28C64B-15PU meets ROHS3 environmental standards, making it suitable for applications subject to RoHS regulations. The original AT28C64X-25PC is RoHS non-compliant and may not be acceptable for regulated markets.

Q: Is the longer write cycle time of the AT28C64B-15PU a concern?

A: The 10 ms write cycle time is acceptable for most EEPROM applications. Applications requiring frequent rapid writes should evaluate the impact on programming throughput.

Q: What is the base product number for both parts?

A: Both the AT28C64X-25PC and AT28C64B-15PU share the base product number AT28C64, indicating they are part of the same memory family with compatible core functionality.