AT29C256-20JC Equivalent & Substitute Parts

Part Overview

The AT29C256-20JC is a 256Kbit parallel FLASH memory IC manufactured by Microchip Technology, housed in a 32-PLCC package with 200 ns access time. This device is classified as obsolete, making substitute components necessary for new designs and production continuity. The part operates within the 4.5V to 5.5V supply range and is suitable for applications requiring non-volatile parallel memory storage in legacy systems.

Key Parameters

Parameter	Value
Memory Size	256Kbit
Memory Organization	32K x 8
Memory Interface	Parallel
Access Time	200 ns
Write Cycle Time	10ms
Voltage Supply	4.5V ~ 5.5V
Package Type	32-PLCC (J-Lead)
Operating Temperature	0°C ~ 70°C
Memory Type	Non-Volatile FLASH

Substitute Part Grouping Explanation

Substitution of the AT29C256-20JC is determined by the following critical parameters:

Package Compatibility: Both parts must use 32-PLCC (J-Lead) surface mount packaging to ensure mechanical and electrical pin compatibility
Voltage Supply Range: Substitute parts must operate within 4.5V to 5.5V to maintain system compatibility
Memory Interface: Parallel interface is mandatory for direct functional replacement
Operating Temperature Range: 0°C to 70°C compatibility ensures thermal envelope alignment
Non-Volatile FLASH Technology: Memory type and format must remain consistent

The SST39SF010A-55-4C-NHE meets all substitution criteria while offering enhanced specifications including higher memory capacity (1Mbit), faster access time (55 ns), and active product status with current manufacturing support.

Parameter Comparison

Parameter	AT29C256-20JC	SST39SF010A-55-4C-NHE
Memory Size	256Kbit	1Mbit
Memory Organization	32K x 8	128K x 8
Memory Interface	Parallel	Parallel
Access Time	200 ns	55 ns
Write Cycle Time	10ms	20µs
Voltage Supply	4.5V ~ 5.5V	4.5V ~ 5.5V
Package Type	32-PLCC (J-Lead)	32-PLCC (J-Lead)
Operating Temperature	0°C ~ 70°C (TC)	0°C ~ 70°C (TA)
Product Status	Obsolete	Active
RoHS Compliance	Non-compliant	ROHS3 Compliant

Engineering Selection Recommendations

The SST39SF010A-55-4C-NHE is the qualified substitute for AT29C256-20JC applications. Selection is based on:

Product Status: The substitute maintains active manufacturing status, ensuring long-term availability and supply chain continuity
Regulatory Compliance: ROHS3 compliance of the substitute aligns with current environmental and regulatory requirements, whereas the original part is non-compliant
Electrical Compatibility: Identical voltage supply range (4.5V ~ 5.5V) and parallel interface enable direct functional replacement
Package Compatibility: Both devices use 32-PLCC (J-Lead) packaging, maintaining mechanical fit and pin assignment alignment
Performance Enhancement: The substitute provides superior access time (55 ns vs. 200 ns) and faster write cycle time (20µs vs. 10ms), delivering performance improvement without design modification

Frequently Asked Questions (FAQ)

Q: Can the SST39SF010A-55-4C-NHE directly replace the AT29C256-20JC in existing designs?

A: Yes. Both devices share identical package type (32-PLCC), voltage supply range (4.5V ~ 5.5V), operating temperature range (0°C ~ 70°C), and parallel memory interface. Pin compatibility is maintained, allowing direct substitution without circuit modification.

Q: What is the primary reason for substituting the AT29C256-20JC?

A: The AT29C256-20JC is classified as obsolete. The SST39SF010A-55-4C-NHE is an active product with current manufacturing support, ensuring availability for new production and long-term supply chain stability.

Q: How do memory capacity differences affect substitution?

A: The SST39SF010A-55-4C-NHE provides 1Mbit capacity versus 256Kbit in the original part. This increased capacity is backward compatible for applications requiring the original 256Kbit footprint, as the substitute can address the full original memory space while providing additional capacity.

Q: Are there compliance differences between these parts?

A: Yes. The AT29C256-20JC is RoHS non-compliant, while the SST39SF010A-55-4C-NHE is ROHS3 compliant. For applications subject to RoHS regulations, the substitute is the required choice.

Q: What performance improvements does the substitute offer?

A: The SST39SF010A-55-4C-NHE delivers 55 ns access time compared to 200 ns, and 20µs write cycle time compared to 10ms. These improvements enhance system performance without requiring design changes.

Q: Is the 32-PLCC package identical between both parts?

A: Both parts use 32-PLCC (J-Lead) surface mount packaging. Physical dimensions are compatible: AT29C256-20JC measures 13.97x11.43mm, while SST39SF010A-55-4C-NHE measures 11.43x13.97mm (rotated orientation). Pin assignment and electrical connectivity remain identical.

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