AT27C256R-45PC Equivalent & Substitute Parts

Part Overview

The AT27C256R-45PC is a 256Kbit EPROM (Erasable Programmable Read-Only Memory) in 28-DIP packaging manufactured by Microchip Technology. This part operates with a 45 ns access time and is designed for parallel memory interface applications requiring non-volatile storage. The AT27C256R-45PC is classified as obsolete, making identification of compatible substitutes essential for system maintenance, repair, and legacy equipment support.

Substiute Parts

AT27C256R-45PC

Microchip TechnologyIn Stock: 1583AT27C256R-45PC Datasheet

Current PartRFQ

AT27C256R-70PU

Microchip TechnologyIn Stock: 6959AT27C256R-70PU Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the AT27C256R-45PC is determined by strict equivalence in the following parameters:

• Memory capacity (256Kbit) and organization (32K x 8)
• Memory format (EPROM - OTP technology)
• Parallel interface architecture
• Supply voltage range (4.5V ~ 5.5V)
• Physical package (28-DIP with 0.600" pitch)
• Through-hole mounting compatibility

The AT27C256R-70PU qualifies as a direct substitute based on matching all core electrical and mechanical specifications. The primary difference is access time (70 ns versus 45 ns), which represents a performance trade-off acceptable in most legacy applications where the original part is no longer available.

Parameter Comparison

Engineering Selection Recommendations

The AT27C256R-70PU is the qualified substitute for the AT27C256R-45PC based on the following factors:

• Both parts share identical memory capacity, organization, and parallel interface specifications
• Both operate within the same supply voltage range (4.5V ~ 5.5V)
• Both use the same 28-DIP through-hole package with matching pinout and mechanical dimensions
• The AT27C256R-70PU is currently in active production status, ensuring availability for replacement applications
• The AT27C256R-70PU carries ROHS3 compliance certification, meeting modern environmental and regulatory standards
• The extended operating temperature range of the substitute (-40°C ~ 85°C) provides broader environmental compatibility compared to the original part (0°C ~ 70°C)

The 25 ns difference in access time (70 ns versus 45 ns) represents a performance degradation that is acceptable in legacy system applications where the original part is no longer manufactured.

Frequently Asked Questions (FAQ)

Q: Can the AT27C256R-70PU be used as a direct replacement for the AT27C256R-45PC?

A: Yes. Both parts are 256Kbit EPROM devices with identical memory organization (32K x 8), parallel interface, supply voltage requirements (4.5V ~ 5.5V), and 28-DIP package specifications. The parts are pin-compatible and mechanically interchangeable.

Q: What is the significance of the access time difference between these parts?

A: Access time specifies the delay from address setup to valid data output. The AT27C256R-45PC provides 45 ns access time, while the AT27C256R-70PU provides 70 ns. In most legacy applications, the slower access time of the substitute does not impact system performance. Applications with strict timing requirements should evaluate system-level timing margins before substitution.

Q: Are there any compliance differences between these parts?

A: The AT27C256R-45PC is RoHS non-compliant, while the AT27C256R-70PU is ROHS3 compliant. Both parts are REACH unaffected and carry the same ECCN and HTSUS classifications. The substitute part meets current environmental and regulatory standards.

Q: Does the operating temperature range difference affect substitution?

A: The AT27C256R-70PU operates across -40°C ~ 85°C, compared to the original part's 0°C ~ 70°C range. This extended range provides greater environmental flexibility and does not restrict substitution in applications using the original temperature specification.

Q: Are the package dimensions identical?

A: Yes. Both parts use 28-DIP packaging with 0.600" (15.24mm) pitch. The physical dimensions, pin spacing, and through-hole mounting requirements are identical, ensuring direct PCB compatibility without layout modifications.