AT28HC256-90SA Equivalent & Substitute Parts

Part Overview

The AT28HC256-90SA is a 256Kbit parallel EEPROM memory integrated circuit manufactured by Microchip Technology in a 28-SOIC surface mount package. This device is classified as obsolete and is no longer in active production. The part operates with a 90 nanosecond access time and supports standard 4.5V to 5.5V supply voltage operation across an extended temperature range of -40°C to 125°C.

Due to its obsolete status, locating replacement inventory from original sources becomes increasingly difficult. Identifying equivalent substitute parts ensures design continuity and maintains access to compatible memory solutions with equivalent or improved electrical characteristics.

Substiute Parts

AT28HC256-90SA

Microchip TechnologyIn Stock: 682AT28HC256-90SA Datasheet

Current PartRFQ

AT28HC256F-90SU

Microchip TechnologyIn Stock: 939AT28HC256F-90SU Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the AT28HC256-90SA is determined by strict equivalence across the following critical parameters:

Memory Capacity and Organization: The substitute part must provide 256Kbit capacity in a 32K x 8 organization to maintain direct functional compatibility with existing circuit designs.

Interface and Protocol: The parallel interface requirement is non-negotiable. The substitute must support identical address and data bus configurations without requiring circuit modifications.

Package and Pinout: The 28-SOIC surface mount package with 0.295" width (7.50mm) ensures mechanical and electrical compatibility with existing PCB layouts. Pin-to-pin compatibility is mandatory.

Electrical Specifications: Supply voltage range of 4.5V to 5.5V and access time of 90 nanoseconds establish the baseline performance envelope. Substitute parts meeting or exceeding these specifications maintain system-level compatibility.

Technology Platform: EEPROM technology classification ensures consistent non-volatile memory behavior and write cycle characteristics required for the application.

The AT28HC256F-90SU qualifies as a direct substitute based on full alignment with these parameters.

Parameter Comparison

Engineering Selection Recommendations

The AT28HC256F-90SU is the qualified substitute for the obsolete AT28HC256-90SA based on the following engineering criteria:

Functional Equivalence: Both parts share identical memory capacity, organization, interface type, and access time specifications. Pin-to-pin compatibility is maintained, enabling direct replacement without circuit redesign.

Product Lifecycle Status: The AT28HC256F-90SU maintains active production status with Microchip Technology, ensuring long-term availability and supply chain reliability. The original AT28HC256-90SA is obsolete, making the substitute the only viable path for continued component sourcing.

Regulatory Compliance: The substitute part achieves ROHS3 compliance, meeting current environmental and regulatory requirements. The original part is non-compliant with modern standards.

Performance Characteristics: The substitute demonstrates improved write cycle time (3ms versus 10ms), providing faster programming capability. The operating temperature range of -40°C to 85°C covers standard industrial and commercial applications. Applications requiring the full -40°C to 125°C range of the original part must evaluate temperature-specific requirements against the substitute's specification.

Electrical Compatibility: Identical supply voltage range and access time ensure seamless integration into existing designs without signal integrity or timing modifications.

Frequently Asked Questions (FAQ)

Q: Can the AT28HC256F-90SU be used as a direct replacement for the AT28HC256-90SA without PCB modifications?

A: Yes. Both parts use the 28-SOIC package with identical pinout and electrical interface specifications. No PCB layout changes are required for mechanical or electrical compatibility.

Q: What is the difference in write cycle time between these parts?

A: The AT28HC256-90SA specifies a 10ms write cycle time, while the AT28HC256F-90SU specifies 3ms. The substitute provides faster write performance. Applications with timing-critical write operations benefit from this improvement.

Q: Does the operating temperature range difference affect substitution?

A: The AT28HC256-90SA operates from -40°C to 125°C, while the AT28HC256F-90SU operates from -40°C to 85°C. For applications requiring operation above 85°C, the substitute does not meet the thermal specification. Standard industrial and commercial applications operating within 0°C to 70°C experience no functional impact.

Q: Are the supply voltage requirements identical?

A: Yes. Both parts require 4.5V to 5.5V supply voltage. No power supply modifications are necessary when substituting the AT28HC256F-90SU for the AT28HC256-90SA.

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

A: The AT28HC256-90SA is RoHS non-compliant, while the AT28HC256F-90SU is ROHS3 compliant. For new designs or applications subject to environmental regulations, the substitute meets current compliance requirements. Existing designs using the original part are not affected by this difference.

Q: Is the 90 nanosecond access time maintained in the substitute?

A: Yes. Both parts specify 90ns access time. System timing and signal propagation characteristics remain unchanged when substituting the AT28HC256F-90SU.

Q: What packaging format is used for both parts?

A: Both the AT28HC256-90SA and AT28HC256F-90SU are supplied in 28-SOIC surface mount packages with 0.295" width (7.50mm). Packaging is identical, supporting direct board-level replacement.