AT27C256R-90PI Equivalent & Substitute Parts

Part Overview

The AT27C256R-90PI is a 256Kbit parallel EPROM (Erasable Programmable Read-Only Memory) manufactured by Microchip Technology in a 28-DIP package with 90 ns access time. This part is classified as obsolete, making substitute components necessary for new designs and ongoing production support. The AT27C256R-90PI operates across the industrial temperature range of -40°C to 85°C and requires a 4.5V to 5.5V supply voltage. Due to its obsolete status and non-RoHS compliance, identifying compatible alternatives is essential for system continuity and regulatory adherence.

Substiute Parts

AT27C256R-90PI

Microchip TechnologyIn Stock: 994AT27C256R-90PI Datasheet

Current PartRFQ

AT27C256R-70PU

Microchip TechnologyIn Stock: 6959AT27C256R-70PU Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the AT27C256R-90PI is determined by the following critical parameters:

• Memory Capacity & Organization: 256Kbit, 32K x 8 configuration
• Memory Technology: EPROM - OTP (One-Time Programmable)
• Interface Type: Parallel interface
• Package Compatibility: 28-DIP form factor with identical pin configuration
• Voltage Requirements: 4.5V ~ 5.5V supply range
• Operating Temperature Range: -40°C ~ 85°C
• Access Time: Equal to or faster than 90 ns

The AT27C256R-70PU qualifies as a direct substitute because it maintains identical memory capacity, organization, interface, package, voltage, and temperature specifications while offering improved access time (70 ns versus 90 ns). Faster access time ensures backward compatibility with systems designed for the 90 ns variant.

Parameter Comparison

Engineering Selection Recommendations

The AT27C256R-70PU is the qualified substitute for the AT27C256R-90PI based on the following factors:

Product Status: The AT27C256R-70PU maintains active product status with verified programmability, whereas the main part is obsolete. This ensures long-term availability and supply chain continuity.

Compliance & Certifications: The substitute achieves ROHS3 compliance, addressing regulatory requirements that the original part does not meet. Both parts maintain REACH Unaffected and EAR99 ECCN classifications.

Performance Compatibility: The 70 ns access time of the substitute is faster than the 90 ns specification of the main part, ensuring full backward compatibility. Systems designed for 90 ns operation will function correctly with the faster substitute without modification.

Electrical & Mechanical Equivalence: Identical voltage supply range, operating temperature range, memory capacity, organization, interface type, and 28-DIP package ensure direct pin-for-pin compatibility with no circuit redesign required.

Frequently Asked Questions (FAQ)

Q: Can the AT27C256R-70PU be used as a direct replacement for the AT27C256R-90PI?

A: Yes. The AT27C256R-70PU is a direct substitute. Both parts share identical memory capacity (256Kbit), organization (32K x 8), parallel interface, voltage requirements (4.5V ~ 5.5V), operating temperature range (-40°C ~ 85°C), and 28-DIP package. The faster 70 ns access time of the substitute ensures compatibility with systems designed for the 90 ns variant.

Q: What is the primary difference between these two parts?

A: The main differences are access time (70 ns versus 90 ns), product status (active versus obsolete), and RoHS compliance (ROHS3 compliant versus non-compliant). The faster access time and active status make the AT27C256R-70PU the preferred choice for new designs and production continuity.

Q: Are there any package or pinout differences?

A: No. Both parts use the 28-DIP (0.600", 15.24mm) package with identical through-hole mounting. Pin configuration and mechanical dimensions are equivalent, allowing direct socket replacement without PCB modification.

Q: Will the faster access time of the substitute cause any compatibility issues?

A: No. Faster access time is backward compatible. Systems designed for 90 ns operation will function correctly with the 70 ns substitute without timing violations or circuit modifications.

Q: What certifications apply to the substitute part?

A: The AT27C256R-70PU is ROHS3 compliant, REACH Unaffected, and classified as EAR99 for export control purposes. These certifications align with current regulatory requirements for electronic components.