AT29C256-90PC Equivalent & Substitute Parts

Part Overview

The AT29C256-90PC is a 256Kbit parallel FLASH memory IC in 28-DIP packaging manufactured by Microchip Technology. This device operates with a 90 ns access time and supports 4.5V to 5.5V supply voltage across a 0°C to 70°C operating temperature range. The product is classified as obsolete, making substitute components necessary for new designs and ongoing system support where original stock is unavailable.

Substiute Parts

AT29C256-90PC

Microchip TechnologyIn Stock: 1388AT29C256-90PC Datasheet

Current PartRFQ

AT27C512R-70PU

Microchip TechnologyIn Stock: 6889AT27C512R-70PU Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the AT29C256-90PC is based on the following critical parameters:

• Package Compatibility: Both main and substitute parts must use 28-DIP (0.600", 15.24mm) through-hole packaging to ensure direct socket compatibility
• Voltage Supply Range: Substitute parts must operate within 4.5V to 5.5V to maintain system compatibility
• Memory Interface: Parallel interface is required for pin-level compatibility
• Non-Volatile Memory Type: Substitute must retain data without power

The AT27C512R-70PU qualifies as a substitute based on matching package, voltage supply range, and parallel memory interface. While the substitute offers higher memory capacity (512Kbit vs 256Kbit) and faster access time (70 ns vs 90 ns), these represent functional improvements rather than incompatibilities.

Parameter Comparison

Engineering Selection Recommendations

The AT27C512R-70PU is an active product with ROHS3 compliance, addressing the obsolescence status of the AT29C256-90PC. Both devices share identical package geometry, voltage supply specifications, and parallel memory interface, enabling direct socket substitution in 28-DIP through-hole applications.

The substitute provides extended operating temperature range (-40°C to 85°C versus 0°C to 70°C) and improved access time (70 ns versus 90 ns), representing functional enhancements. The higher memory capacity (512Kbit versus 256Kbit) requires address line utilization verification in the target application.

Selection of the AT27C512R-70PU is appropriate for applications requiring active product status and modern compliance certifications. Applications with strict memory size constraints or legacy firmware dependencies must evaluate address decoding requirements.

Frequently Asked Questions (FAQ)

Q: Can the AT27C512R-70PU directly replace the AT29C256-90PC in existing designs?

A: Direct socket replacement is possible due to identical 28-DIP package geometry and through-hole mounting. Voltage supply (4.5V to 5.5V) and parallel interface requirements are met. Address line utilization must be verified, as the substitute provides 64K x 8 organization versus the original 32K x 8.

Q: What are the key differences between FLASH and EPROM memory types in this substitution?

A: The AT29C256-90PC uses FLASH technology with 10 ms write cycle time. The AT27C512R-70PU uses EPROM - OTP (One-Time Programmable) technology. Both are non-volatile and support parallel interfaces. Programming methodology and cycle characteristics differ between technologies.

Q: Does the extended operating temperature range of the substitute affect compatibility?

A: The substitute's operating range (-40°C to 85°C) encompasses the original specification (0°C to 70°C). This represents an expansion of operating conditions and does not create incompatibility for applications within the original temperature range.

Q: How does the faster access time (70 ns vs 90 ns) impact system integration?

A: The substitute's 70 ns access time is faster than the original 90 ns specification. Systems designed for 90 ns access time will operate correctly with the faster substitute. No timing adjustments are required.

Q: What compliance considerations apply to this substitution?

A: The AT29C256-90PC is RoHS non-compliant. The AT27C512R-70PU is ROHS3 compliant. Applications subject to RoHS requirements must use the substitute. Legacy systems without compliance mandates may use either device based on availability and functional requirements.

Q: Are there inventory or availability differences between these parts?

A: The AT29C256-90PC is classified as obsolete with 1325 pieces in stock. The AT27C512R-70PU is an active product with 6837 pieces in stock, providing superior long-term availability for ongoing production and support.