AT28C256-20JC EEPROM Memory IC Equivalent & Substitute Parts

Part Overview

The AT28C256-20JC is a 256Kbit parallel EEPROM memory IC manufactured by Microchip Technology, housed in a 32-PLCC package with 200 ns access time. This component is classified as obsolete, making substitute parts necessary for new designs and ongoing production requirements. The part operates within a 4.5V to 5.5V supply voltage range and supports standard parallel memory interface protocols common in legacy embedded systems and industrial applications.

Key Parameters

Parameter	Value
Memory Size	256Kbit
Memory Organization	32K x 8
Memory Format	EEPROM
Memory Interface	Parallel
Access Time	200 ns
Write Cycle Time	10 ms
Voltage Supply Range	4.5V ~ 5.5V
Package Type	32-PLCC (13.97x11.43)
Operating Temperature	0°C ~ 70°C
Mounting Type	Surface Mount

Substitute Part Grouping Explanation

Substitution eligibility for the AT28C256-20JC is determined by the following critical parameters:

Memory Capacity & Organization: Must maintain 256Kbit capacity with 32K x 8 organization to ensure address and data bus compatibility
Memory Format & Interface: Must be EEPROM with parallel interface to preserve existing circuit topology and firmware compatibility
Package & Pinout: Must use 32-PLCC package with identical physical dimensions (13.97x11.43) for PCB socket compatibility
Voltage Supply Range: Must support 4.5V ~ 5.5V operation to function within existing power distribution systems
Write Cycle Time: Must maintain 10 ms write cycle time for firmware programming compatibility

The AT28C256-15JU-043 qualifies as a direct substitute based on these parameters. While it offers improved access time (150 ns versus 200 ns) and extended operating temperature range (-40°C ~ 85°C versus 0°C ~ 70°C), these enhancements are backward-compatible with the original specification and do not create functional conflicts.

Parameter Comparison

Parameter	AT28C256-20JC (Main Part)	AT28C256-15JU-043 (Substitute)	Compatibility
Memory Size	256Kbit	256Kbit	Identical
Memory Organization	32K x 8	32K x 8	Identical
Memory Format	EEPROM	EEPROM	Identical
Memory Interface	Parallel	Parallel	Identical
Access Time	200 ns	150 ns	Substitute is faster
Write Cycle Time	10 ms	10 ms	Identical
Voltage Supply Range	4.5V ~ 5.5V	4.5V ~ 5.5V	Identical
Package Type	32-PLCC (13.97x11.43)	32-PLCC (13.97x11.43)	Identical
Operating Temperature	0°C ~ 70°C	-40°C ~ 85°C	Substitute has wider range
Product Status	Obsolete	Active	Substitute is in production
RoHS Compliance	Non-compliant	ROHS3 Compliant	Substitute meets current standards

Engineering Selection Recommendations

The AT28C256-15JU-043 is the recommended substitute for the obsolete AT28C256-20JC based on the following engineering criteria:

Product Status: The AT28C256-15JU-043 maintains active production status, ensuring long-term availability and supply chain stability compared to the obsolete main part.

Compliance & Certifications: The substitute achieves ROHS3 compliance, meeting current environmental and regulatory requirements. Both parts maintain identical REACH Unaffected and EAR99 ECCN classifications.

Functional Compatibility: All critical electrical parameters—memory capacity, organization, interface type, voltage supply range, and write cycle time—remain unchanged, ensuring direct functional equivalence without circuit modification.

Performance Enhancement: The improved 150 ns access time provides faster read operations while maintaining full backward compatibility with systems designed for 200 ns operation.

Temperature Range Extension: The wider operating temperature range (-40°C ~ 85°C) accommodates industrial and extended-temperature applications beyond the original specification.

Frequently Asked Questions (FAQ)

Q: Can the AT28C256-15JU-043 be used as a direct replacement without circuit modifications?

A: Yes. The substitute maintains identical memory capacity, organization, parallel interface, voltage supply range, write cycle time, and 32-PLCC package dimensions. No circuit modifications are required.

Q: What is the significance of the improved 150 ns access time in the substitute?

A: The faster access time is a performance enhancement that does not create compatibility issues. Systems designed for 200 ns operation will function correctly with the 150 ns part, as the substitute meets or exceeds all timing requirements.

Q: Does the extended operating temperature range affect compatibility?

A: No. The wider temperature range (-40°C ~ 85°C) is a superset of the original specification (0°C ~ 70°C). The substitute operates correctly within the original temperature limits and extends capability for broader environmental conditions.

Q: Why is RoHS compliance important for this substitution?

A: RoHS3 compliance ensures the substitute meets current environmental regulations and manufacturing standards. This is particularly important for new designs and products subject to regulatory requirements in target markets.

Q: Are there any package or pinout differences between the main part and substitute?

A: No. Both parts use the identical 32-PLCC package with dimensions of 13.97x11.43 mm. Pinout compatibility is guaranteed, allowing socket-level replacement.

Q: What inventory status should be considered when selecting between these parts?

A: The AT28C256-15JU-043 has 959 units in stock with active production status, providing reliable availability. The main part has 1412 units in stock but is obsolete, making future procurement uncertain.

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