AT29C256-70PC Equivalent & Substitute Parts

Part Overview

The AT29C256-70PC is a 256Kbit parallel FLASH memory IC manufactured by Microchip Technology, housed in a 28-DIP package with 70 ns access time. This component is classified as obsolete, making equivalent or substitute parts necessary for new designs or production continuity. The part operates within a 4.5V to 5.5V supply voltage range and supports through-hole mounting applications requiring non-volatile FLASH memory storage.

Substiute Parts

AT29C256-70PC

Microchip TechnologyIn Stock: 1561AT29C256-70PC Datasheet

Current PartRFQ

AT27C512R-70PU

Microchip TechnologyIn Stock: 6889AT27C512R-70PU Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the AT29C256-70PC is determined by the following critical parameters:

• Package Compatibility: Both parts must use 28-DIP (0.600", 15.24mm) through-hole packaging to ensure mechanical and electrical socket compatibility
• Memory Interface: Parallel interface requirement must be maintained for signal compatibility
• Access Time: 70 ns specification must be met or exceeded (lower values acceptable)
• Voltage Supply: 4.5V ~ 5.5V operating range must be supported
• Memory Organization: The substitute must provide sufficient address and data line compatibility

The AT27C512R-70PU qualifies as a substitute based on matching package type, parallel interface, access time specification, and voltage supply range. While the AT27C512R-70PU offers higher memory capacity (512Kbit vs. 256Kbit), this represents a functional superset suitable for applications requiring the original part's specifications.

Parameter Comparison

Engineering Selection Recommendations

The AT27C512R-70PU is available as an active product with current manufacturing support, whereas the AT29C256-70PC is obsolete. The substitute part maintains electrical compatibility through identical access time (70 ns), voltage supply range (4.5V ~ 5.5V), and package form factor (28-DIP).

The AT27C512R-70PU provides ROHS3 compliance, addressing regulatory requirements that the original part does not meet. The extended operating temperature range (-40°C ~ 85°C) of the substitute exceeds the original specification (0°C ~ 70°C), providing broader environmental suitability.

The memory technology differs between parts: the original uses FLASH memory while the substitute uses EPROM - OTP (One-Time Programmable). This distinction affects programming methodology and reprogrammability characteristics. The higher memory capacity (512Kbit vs. 256Kbit) of the substitute accommodates applications requiring expanded storage without additional component changes.

Frequently Asked Questions (FAQ)

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

A: Yes, from a package and electrical interface perspective. Both parts use 28-DIP through-hole packaging, support parallel memory interface, operate at 4.5V ~ 5.5V, and provide 70 ns access time. However, the memory technology difference (FLASH vs. EPROM - OTP) and increased capacity require verification that the application's programming and memory access patterns are compatible with the substitute.

Q: What is the primary difference between FLASH and EPROM - OTP memory technologies?

A: FLASH memory (AT29C256-70PC) supports in-circuit reprogramming and erasure. EPROM - OTP (AT27C512R-70PU) is one-time programmable, meaning once programmed, the data cannot be erased or reprogrammed without specialized equipment. This distinction is critical for applications requiring field updates or multiple programming cycles.

Q: Does the higher memory capacity of the AT27C512R-70PU create compatibility issues?

A: The 512Kbit capacity (64K x 8 organization) of the substitute is a functional superset of the 256Kbit capacity (32K x 8) of the original part. Applications using only the lower address space will function correctly. However, circuit designs must account for the additional address lines if the full capacity is to be utilized.

Q: Are there compliance differences between these parts?

A: Yes. The AT27C512R-70PU is ROHS3 compliant, while the AT29C256-70PC is RoHS non-compliant. For applications subject to RoHS regulations, the substitute part satisfies compliance requirements. Both parts are REACH unaffected.

Q: What is the operating temperature range difference?

A: The AT29C256-70PC operates from 0°C to 70°C, while the AT27C512R-70PU operates from -40°C to 85°C. The substitute provides a wider temperature envelope, suitable for applications requiring extended environmental operating conditions.