AT29C256-90PI Equivalent & Substitute Parts

Part Overview

The AT29C256-90PI is a 256Kbit parallel FLASH memory IC manufactured by Microchip Technology, housed in a 28-DIP package with 90 ns access time. This device is classified as obsolete, making substitute components necessary for new designs and ongoing production requirements. The part operates across a supply voltage range of 4.5V to 5.5V and supports operating temperatures from -40°C to 85°C.

Substiute Parts

AT29C256-90PI

Microchip TechnologyIn Stock: 7859AT29C256-90PI Datasheet

Current PartRFQ

AT27C512R-70PU

Microchip TechnologyIn Stock: 6889AT27C512R-70PU Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the AT29C256-90PI is determined by the following critical parameters:

• Package Compatibility: Both main and substitute parts must use 28-DIP (0.600", 15.24mm) through-hole packaging to ensure mechanical fit on existing PCBs
• Memory Interface: Parallel interface requirement must be maintained for signal compatibility
• Voltage Supply Range: 4.5V ~ 5.5V compatibility ensures electrical interoperability
• Operating Temperature Range: -40°C ~ 85°C specification must be met or exceeded
• Access Time: The substitute part AT27C512R-70PU provides 70 ns access time, which is faster than the original 90 ns specification, ensuring timing compatibility in applications designed for the AT29C256-90PI

The AT27C512R-70PU qualifies as a substitute based on matching package, interface, voltage, and temperature specifications. While the substitute uses EPROM technology (versus FLASH in the original), both are non-volatile memory types with parallel interfaces suitable for this application category.

Parameter Comparison

Engineering Selection Recommendations

The AT27C512R-70PU is available as an active product with ROHS3 compliance, addressing the obsolescence status of the AT29C256-90PI. The substitute maintains identical package, voltage, temperature, and interface specifications. The faster 70 ns access time of the substitute provides improved timing margin for existing circuit designs. The increased memory capacity (512Kbit versus 256Kbit) does not create compatibility issues in applications where address space is not fully utilized.

Selection of the AT27C512R-70PU is appropriate for applications requiring continued supply of functionally equivalent memory components with improved compliance status and active product availability.

Frequently Asked Questions (FAQ)

Q: Can the AT27C512R-70PU directly replace the AT29C256-90PI on existing PCBs?

A: Yes. Both parts use identical 28-DIP packaging with 0.600" (15.24mm) spacing, enabling direct through-hole mounting on existing circuit boards without PCB modifications.

Q: Are the electrical specifications compatible?

A: Yes. Both parts operate at 4.5V ~ 5.5V supply voltage and -40°C ~ 85°C temperature range. The substitute's 70 ns access time is faster than the original 90 ns specification, ensuring timing compatibility.

Q: What is the difference between FLASH and EPROM memory types?

A: Both are non-volatile memory technologies. FLASH memory (AT29C256-90PI) supports in-circuit erasure and reprogramming. EPROM - OTP (AT27C512R-70PU) is one-time programmable. For applications requiring reprogramming capability, memory technology differences must be evaluated against specific use requirements.

Q: Does the larger memory size of the substitute create compatibility issues?

A: No. The AT27C512R-70PU provides 512Kbit capacity (64K x 8 organization) compared to the AT29C256-90PI's 256Kbit (32K x 8). Applications using only the lower address space of the substitute will operate without issues. Address decoding logic must accommodate the additional address lines if full memory capacity is to be utilized.

Q: What is the significance of the RoHS compliance difference?

A: The AT29C256-90PI is RoHS non-compliant, while the AT27C512R-70PU is ROHS3 compliant. For applications subject to RoHS regulations or customer requirements, the substitute provides compliance alignment with current environmental standards.

Q: Is the AT27C512R-70PU currently available?

A: Yes. The AT27C512R-70PU is classified as an active product with verified programmability and current inventory availability, addressing the obsolescence status of the AT29C256-90PI.