Microchip Technology AT27C020-90JC

Overview

AT27C020-90JC from Atmel is a 2-Mbit (256K × 8) one-time programmable EPROM optimized for fast read access and low-power operation in embedded firmware storage applications. It features 55 ns read access time, 5 V ±10% single-supply operation, and JEDEC-standard 32-lead PLCC packaging. Designed for microprocessor systems requiring reliable nonvolatile code storage without wait states, it supports commercial temperature range (0°C to 70°C).

For engineers reviewing the AT27C020-90JC datasheet, AT27C020-90JC pinout, AT27C020-90JC application, or AT27C020-90JC equivalent, key selection considerations include its 90 ns access timing grade, Rapid™ programming algorithm (100 µs/byte), CMOS/TTL compatibility, integrated product identification code, and dual-line control (CE/OE) architecture for bus contention management.

Technical Context

The AT27C020-90JC implements a two-line control interface with Chip Enable (CE) and Output Enable (OE), enabling flexible bus arbitration and high-speed read cycles without external wait-state generation. Its address space spans A0–A17 (18-bit), supporting full 256K-byte access with byte-level output drivers (O0–O7).

Programming requires VPP = 12.0 V ±0.5 V and VCC = 6.5 V ±0.25 V, with a verified 100 µs PGM pulse width and up to 10 reprogramming attempts per byte. Product identification uses A9 at 12 V and A0 toggling to select manufacturer (0x1E) or device code (0x86) bytes.

Key Specifications

Pinout & Package

AT27C020-90JC is packaged in a 32-lead Plastic J-Leaded Chip Carrier (PLCC), JEDEC MS-016 AE compliant, with 1.27 mm pitch and surface-mount footprint. Pin 1 is marked by index notch and corner chamfer.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AM27C256B-120DC and MX27C256-12PC, the AT27C020-90JC delivers faster 90 ns access, lower 100 µA standby current, and built-in Rapid™ programming-making it optimal for new designs demanding tighter timing margins and reduced system power.

Availability

AT27C020-90JC is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy embedded system boot ROM, and automotive instrument cluster calibration data applications requiring stable component supply and long-term obsolescence support.

Supply support for AT27C020-90JC 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 (now part of Microchip Technology) is a fabless semiconductor company specializing in microcontrollers, nonvolatile memory, and secure authentication ICs for industrial, automotive, and consumer markets.

The AT27C020 belongs to Atmel's OTP EPROM product line, designed specifically for cost-effective, high-reliability firmware and configuration storage in systems where reprogrammability is unnecessary but data integrity and timing predictability are critical.

FAQ

What is the maximum operating temperature range for the AT27C020-90JC?

The AT27C020-90JC is rated for the commercial temperature range of 0°C to 70°C. This specification is explicitly defined in the Ordering Information table and confirmed in the DC Operating Conditions section of the datasheet. Operation outside this range may result in timing violations or data retention failure. The AT27C020-90JI variant supports -40°C to +85°C, but the -90JC suffix denotes commercial-grade qualification only.

Does the AT27C020-90JC require a separate programming voltage during normal read operation?

No, the AT27C020-90JC operates from a single 5 V ±10% supply during read mode. VPP (12.0 V ±0.5 V) is required only during programming and product identification modes. The datasheet specifies that VPP must be applied after VCC and removed before VCC to avoid latch-up. In read mode, VPP can be tied to VCC or left unconnected depending on system design, but it is not actively used.

How is the Integrated Product Identification Code accessed on the AT27C020-90JC?

The Integrated Product Identification Code on the AT27C020-90JC is accessed by asserting VPP = 12.0 V ±0.5 V, holding A1–A17 low, setting A9 to 12 V (VH), and toggling A0: low for Manufacturer ID (0x1E), high for Device Code (0x86). This function is detailed in the "Product Identification" operating mode table and confirmed in Figure 4 of the datasheet. No external programming hardware is needed-only controlled voltage application.

Can the AT27C020-90JC be used as a direct replacement for the AT27C020-70JC in an existing design?

Yes, the AT27C020-90JC is functionally and pin-compatible with the AT27C020-70JC, differing only in guaranteed maximum read access time (90 ns vs. 70 ns). Both share identical pinout, voltage requirements, programming algorithm, and temperature range. Systems designed for the -70JC will operate reliably with the -90JC, though timing裕度 decreases by 20 ns-verify setup/hold margins if operating near maximum CPU frequency.

What decoupling capacitance is required for stable operation of the AT27C020-90JC?

The AT27C020-90JC requires a minimum 0.1 µF high-frequency ceramic capacitor between VCC and GND, placed as close to the device pins as possible. For systems with multiple EPROMs, a 4.7 µF bulk electrolytic capacitor is also recommended near the power entry point. These values are specified in the "System Considerations" section to suppress transients during CE transitions and maintain supply stability within datasheet limits.