Microchip Technology AT27C1024-90VC

Overview

AT27C1024-90VC from Microchip Technology (formerly Atmel) is a 1-Mbit one-time programmable EPROM organized as 64K × 16 bits, operating at 5V ±10%, with 90 ns read access time, CMOS/TTL-compatible I/O, and dual-line control (CE/OE) for bus contention avoidance in microprocessor systems.

For engineers reviewing the AT27C1024-90VC datasheet, AT27C1024-90VC pinout, AT27C1024-90VC application, or AT27C1024-90VC equivalent, this page delivers verified timing specs, PDIP/VSOP package mapping, Rapid™ programming behavior, product identification code support, and industrial temperature operation details critical for firmware storage and legacy system upgrades.

Technical Context

The AT27C1024-90VC implements a high-density OTP EPROM architecture with address decoding for A0–A15 and bidirectional 16-bit data outputs O0–O15. Its two-line enable scheme (CE active-low, OE active-low) enables precise output gating without bus contention during high-speed reads.

It supports Rapid™ programming with 100 µs/word typical pulse width at VPP = 13.0 V and VCC = 6.5 V, and includes integrated product identification via A9 voltage sensing (12.0 V ±0.5 V) and A0 toggling to select manufacturer or device code words.

Key Specifications

Pinout & Package

AT27C1024-90VC is supplied in a 40-lead Plastic Thin Small Outline Package (VSOP), 10 mm × 14 mm, JEDEC MO-142 CA compliant, with gull-wing leads and pin 1 indicator marked on top surface.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar OTP EPROM applications.

Compared with AT27C1024-90VC, the PDIP variant offers socket flexibility but larger board area, while the PLCC variant improves thermal performance at the cost of more complex assembly - all three share identical memory organization, timing, and programming behavior.

Availability

AT27C1024-90VC is available at Aetrix Electronics and suitable for industrial control, legacy system restoration, telecom infrastructure, and automotive calibration applications requiring stable component supply across extended product lifecycles.

Supply support for AT27C1024-90VC includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Microchip Technology acquired Atmel in 2016 and maintains full technical and manufacturing continuity for the AT27C1024 family, including long-term support for industrial and automotive variants.

The AT27C1024 series was designed as a high-reliability, pin- and function-compatible upgrade path from 512K EPROMs, targeting firmware storage in resource-constrained 16-/32-bit embedded systems where non-volatility, speed, and longevity are critical.

FAQ

What is the maximum read access time specified for AT27C1024-90VC?

The AT27C1024-90VC has a maximum read access time (tACC) of 90 ns under industrial temperature conditions (-40°C to +85°C) and 5 V ±10% supply. This value is guaranteed across all operating modes when CE and OE are both asserted low, and it directly determines whether WAIT states are needed in host microprocessor interfaces running at 5 MHz or below. The "-90" suffix in the part number explicitly denotes this speed grade.

Does AT27C1024-90VC require a separate programming voltage, and what is its value?

Yes, AT27C1024-90VC requires VPP = 13.0 V ±0.25 V during programming, applied to the VPP pin while VCC is raised to 6.5 V ±0.25 V. This elevated voltage enables Fowler-Nordheim tunneling for reliable one-time programming of the floating-gate cells. The device must never be programmed with VPP = VCC; strict sequencing (VCC before VPP, VPP before removal) is mandatory to prevent damage.

Can AT27C1024-90VC be used as a direct replacement for AT27C516 in existing designs?

Yes, AT27C1024-90VC is explicitly designed as a direct upgrade from the 512K AT27C516, sharing identical pinout in PDIP and PLCC packages and matching DC/AC characteristics except for doubled density (64K×16 vs. 32K×16). In VSOP, pin mapping differs slightly due to package-specific layout, so board-level verification is required - but logic interface, timing, and programming flow remain fully compatible.

What is the purpose of the A9 and A0 pins during product identification mode for AT27C1024-90VC?

During product identification, A9 is biased to 12.0 V ±0.5 V (VID) while A0 is toggled between low and high to select either the Manufacturer Identification Word (A0 = VIL) or Device Code Word (A0 = VIH). Both A1–A15 must be held low. This feature allows automated programmers to verify correct device insertion and firmware algorithm selection without external marking or manual configuration.

How does the dual-line control (CE and OE) architecture benefit system design with AT27C1024-90VC?

The independent CE and OE inputs in AT27C1024-90VC allow precise control over chip activation and output driver enablement. CE gates internal array power and address decoding, while OE controls only the output buffers - enabling bus sharing, partial memory disable, and glitch-free transitions during DMA or multi-master arbitration. This eliminates contention risks common in single-enable EPROMs and simplifies timing closure in high-speed 16-bit data buses.