Microchip Technology AT27C040-90JU-T

Overview

AT27C040-90JU-T from Microchip Technology (formerly Atmel) is a 4 Mb (512K × 8) One-Time Programmable EPROM used for non-volatile program storage in legacy microprocessor systems. It features 90 ns read access time, 5V ±10% single-supply operation, CMOS/TTL-compatible I/O, and industrial temperature range (–40°C to +85°C). Its dual-line control (CE/OE) enables bus contention-free interfacing in high-speed embedded controllers.

For engineers reviewing the AT27C040-90JU-T datasheet, AT27C040-90JU-T pinout, AT27C040-90JU-T application, or AT27C040-90JU-T equivalent, this page delivers verified technical context, JEDEC-standard PLCC-32 package details, rapid programming characteristics (100 μs/byte), standby current (≤100 μA), and real-world use cases in firmware boot memory and configuration storage.

Technical Context

The AT27C040-90JU-T implements a fixed-architecture OTP EPROM with 19-bit address bus (A0–A18) and 8-bit bidirectional data bus (O0–O7), supporting byte-level random access without wait states. Its two-line enable logic (CE active-low, OE active-low) decouples chip selection from output gating-critical for shared-bus microcontroller designs.

Programming requires VPP = 13.0 V ±0.25 V and VCC = 6.5 V ±0.25 V during pulse application, with integrated product identification (0x1E manufacturer code, 0x0B device code) enabling automated programmer recognition. The device uses scaled CMOS technology with 200 mA latchup immunity and 2000 V HBM ESD protection.

Key Specifications

Pinout & Package

AT27C040-90JU-T is supplied in a 32-lead plastic J-leaded chip carrier (PLCC-32), JEDEC MS-016 compliant, with gull-wing leads and pin 1 identifier notch. Package dimensions: 12.47 mm × 14.99 mm × 3.35 mm (D × E × A), lead coplanarity ≤0.10 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT27C040-70JU, the AT27C040-90JU-T trades 20 ns slower access for broader voltage tolerance margin and reduced cost; versus AM27C040-90DC, it substitutes surface-mount PLCC for through-hole PDIP-enabling higher board density but requiring retooling for SMT placement.

Availability

AT27C040-90JU-T is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy microcontroller boot ROM, and telecom line card configuration requiring stable component supply across extended product lifecycles.

Supply support for AT27C040-90JU-T 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 support for legacy Atmel memory products. The company specializes in secure, reliable, and long-lifecycle semiconductor solutions for industrial and aerospace markets.

The AT27C040-90JU-T belongs to Atmel's OTP EPROM product line, designed specifically for cost-sensitive, high-reliability firmware storage in systems where code immutability and long-term data retention (>10 years) are critical design requirements.

FAQ

What is the programming voltage requirement for AT27C040-90JU-T?

The AT27C040-90JU-T requires VPP = 13.0 V ±0.25 V applied to the VPP pin during programming, with VCC simultaneously set to 6.5 V ±0.25 V. These voltages must be applied and removed simultaneously per datasheet Section 6.3. Applying VPP without proper VCC sequencing risks device damage or incomplete programming. The AT27C040-90JU-T does not support in-system programming and must be programmed using a dedicated EPROM programmer.

Is AT27C040-90JU-T pin-compatible with other 32-lead PLCC EPROMs?

Yes, the AT27C040-90JU-T uses the JEDEC-standard 32J PLCC footprint (MS-016, Variation AE) and shares identical pinout with industry-standard 4 Mb EPROMs including the AMD AM27C040 and Intel 27C4000 series. Pin functions (A0–A18, O0–O7, CE, OE, VCC, GND, VPP) match exactly. However, verify VPP voltage tolerance and programming algorithms before substitution, as some variants require 12.5 V or different pulse timing.

Does AT27C040-90JU-T support read-modify-write operations?

No, the AT27C040-90JU-T is a One-Time Programmable EPROM and does not support read-modify-write operations. Once programmed, its contents cannot be electrically erased or rewritten. Data integrity is maintained for >10 years under industrial temperature conditions. For field-upgradable memory, consider flash alternatives like the AT45DB041D, but note that these require different interface logic and timing.

What decoupling capacitors are required for stable AT27C040-90JU-T operation?

The AT27C040-90JU-T requires a 0.1 μF high-frequency ceramic capacitor placed between VCC and GND, mounted as close as possible to the device pins. For systems with multiple EPROMs, add a 4.7 μF bulk electrolytic capacitor near the power entry point. This mitigates transient excursions caused by CE switching and ensures VCC remains within ±10% during rapid read cycles-critical for maintaining tACC ≤90 ns compliance.

How is the manufacturer and device identification accessed on AT27C040-90JU-T?

The AT27C040-90JU-T integrates a product identification code accessible via A9 and A0 during special read mode: hold A1–A18 low, apply VH = 12.0 V ±0.5 V to A9, then toggle A0 low for manufacturer ID (0x1E) or high for device ID (0x0B). This feature is used by automated programmers to auto-detect part type and select correct programming algorithms-ensuring reliable first-pass programming of the AT27C040-90JU-T.