Microchip Technology AT27C400-90JC

Overview

AT27C400-90JC from Atmel is a 4-megabit one-time programmable EPROM (OTP EPROM) organized as 256K × 16 or 512K × 8, with 90 ns read access time, 5V ±10% supply, and PLCC-44 packaging. It supports word-wide or byte-wide configuration via BYTE/VPP pin and operates across industrial temperature range (–40°C to +85°C). Used for firmware storage in 16-/32-bit microprocessor systems requiring nonvolatile, low-latency code execution.

For engineers reviewing the AT27C400-90JC datasheet, AT27C400-90JC pinout, AT27C400-90JC application, or AT27C400-90JC equivalent, key selection criteria include its 90 ns read timing, dual organization flexibility, 100 µA max standby current, JEDEC-standard PLCC-44 package, and Rapid™ programming at 50 µs/word - critical for embedded boot memory and legacy system upgrades.

Technical Context

The AT27C400-90JC implements a CMOS-based OTP EPROM architecture with two-line control (CE/OE), enabling bus contention-free operation in high-speed systems. Its BYTE/VPP pin selects between 256K × 16 (O15/A-1 as data output) and 512K × 8 (O15/A-1 as address A-1) configurations, allowing dynamic interface adaptation to 8-bit or 16-bit data buses.

It features integrated product identification (manufacturer ID 0x1E1E, device ID 0xF4F4), accessed via A9 = 12.0 V and A0 toggling, and supports rapid programming with 50 µs CE pulses and up to 10 retries per word. Standby current is specified at ≤100 µA with VPP = VCC, and active current ≤40 mA at 5 MHz.

Key Specifications

Pinout & Package

AT27C400-90JC is packaged in a 44-lead Plastic J-Leaded Chip Carrier (PLCC), JEDEC MS-018 AC compliant, with 1.27 mm pitch and 16.5 mm × 16.5 mm body size. Pin 1 identified by corner notch; both GND pins (pins 23 and 32) must be connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT27C400-90JC, the AT27C400-90JI offers identical functionality in SOIC for automated assembly, while AM27C400-90DC provides second-source availability at the cost of programming infrastructure changes and loss of electronic ID traceability.

Availability

AT27C400-90JC is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy embedded boot ROM replacement, and automotive diagnostic tool memory requiring stable component supply and long-term obsolescence management.

Supply support for AT27C400-90JC 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

Atmel Corporation was a U.S.-based semiconductor company specializing in microcontrollers, nonvolatile memory, and programmable logic, acquired by Microchip Technology in 2016.

The AT27C400 series was designed as a high-reliability, drop-in OTP EPROM replacement for legacy 27C-series devices, targeting industrial control, instrumentation, and automotive diagnostic systems requiring guaranteed data retention and JEDEC-standard packaging.

FAQ

What is the maximum standby current specification for AT27C400-90JC?

The AT27C400-90JC has a maximum standby current of 100 µA under CMOS conditions (CE = VCC ± 0.3V) with VPP = VCC. This value is measured at VCC = 5V and TA = 25°C, and applies to industrial temperature range operation. The AT27C400-90JC achieves this low quiescent draw through optimized CMOS design and dual-rail isolation, making it suitable for battery-buffered systems where power conservation is critical during idle states.

Does AT27C400-90JC support both 8-bit and 16-bit data bus interfaces?

Yes, the AT27C400-90JC supports both 8-bit and 16-bit data bus interfaces via the BYTE/VPP pin. When BYTE/VPP = VIH, the device operates in 256K × 16 word-wide mode with O0–O15 active. When BYTE/VPP = VIL, it operates in 512K × 8 byte-wide mode, using O0–O7 for lower byte and O15/A-1 as address A-1. This dual-mode capability allows the same AT27C400-90JC to serve in either architecture without redesign.

What programming voltage is required for AT27C400-90JC?

The AT27C400-90JC requires VPP = 12.0 V ± 0.5 V during programming, applied to the BYTE/VPP pin. VCC must be simultaneously present at 6.5 V ± 0.25 V, and VCC must be applied before and removed after VPP. This precise voltage sequencing is mandatory for reliable programming; applying VPP without proper VCC bias risks incomplete cell programming or device damage. The AT27C400-90JC does not support in-system programming and requires dedicated EPROM programmers.

Is AT27C400-90JC pin-compatible with older 27C400 variants?

Yes, the AT27C400-90JC maintains full pin compatibility with industry-standard 27C400-family EPROMs in PLCC-44 packaging, including identical pin functions, spacing, and electrical signaling (TTL/CMOS-compatible I/O). Its 44J footprint matches JEDEC MS-018 AC, ensuring direct socket replacement in legacy systems. However, AT27C400-90JC introduces Rapid™ programming and integrated ID code - features not present in earlier 27C400 versions - without altering pin behavior or timing in read mode.

What is the purpose of the O15/A-1 pin on AT27C400-90JC?

The O15/A-1 pin on AT27C400-90JC is a dual-function terminal whose role depends on BYTE/VPP state. In word-wide mode (BYTE/VPP = VIH), it serves as the O15 data output bit. In byte-wide mode (BYTE/VPP = VIL), it becomes address input A-1, extending addressing to select upper or lower byte within each 16-bit word. This pin enables the AT27C400-90JC to deliver flexible memory mapping without additional address lines, reducing system complexity in mixed-bus architectures.