Microchip Technology AT29C257-70JC-T

Overview

AT29C257-70JC-T from Microchip Technology (formerly Atmel) is a 5-V-only, 256 Kbit (32K × 8) in-system reprogrammable Flash PEROM with 70 ns read access time, 10 ms page program time, and CMOS standby current of 300 µA. It operates across 0°C to 70°C, uses PLCC-32 packaging, and supports hardware/software data protection for embedded firmware storage in microcontroller-based systems.

For engineers reviewing the AT29C257-70JC-T datasheet, AT29C257-70JC-T pinout, AT29C257-70JC-T application, or AT29C257-70JC-T equivalent, key selection criteria include 5V-only programming compatibility, 64-byte page load timing, DATA polling/Toggle Bit end-of-write detection, and pin compatibility with AT29C010A/AT29C512 for memory upgrades.

Technical Context

The AT29C257-70JC-T implements a nonvolatile Flash architecture with internal latching for 64-byte page loads and autonomous erase-program sequencing controlled by an on-chip timer. Its dual-line chip enable (CE) and output enable (OE) logic enables bus contention avoidance during mixed read/write operations.

It supports three distinct operational modes: standard read (CE/OE low, WE high), byte load (WE or CE pulse with OE high), and software-controlled programming/erasure using 3- to 6-byte command sequences at specific addresses (e.g., 5555H/2AAAH). Hardware protection includes VCC sense (<3.8 V inhibition), 5 ms power-on delay, and noise filtering on WE/CE inputs.

Key Specifications

Pinout & Package

AT29C257-70JC-T is housed in a 32-lead Plastic Leaded Chip Carrier (PLCC-32) package with J-bend leads, designed for surface-mount assembly and socketed prototyping. The package provides mechanical robustness and thermal performance suitable for reflow and wave soldering.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Flash memory applications.

Compared with AT29C010A-12JC and SST39SF020A-70-4C-NHE, the AT29C257-70JC-T offers optimal balance of speed (70 ns), density (256 Kbit), and legacy 5V system compatibility - making it ideal for cost-sensitive, volume-manufactured commercial equipment where pin- and timing-matching to existing AT29Cxx designs is critical.

Availability

AT29C257-70JC-T is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy embedded instrumentation, and medical diagnostic device boot memory requiring stable component supply across extended production lifecycles.

Supply support for AT29C257-70JC-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 is a global semiconductor company specializing in microcontrollers, analog devices, and nonvolatile memory solutions, with broad industrial and automotive qualification coverage.

The AT29C257-70JC-T belongs to Microchip's legacy Flash PEROM product line, designed specifically for 5V embedded systems requiring in-system reprogrammability, hardware/software write protection, and pin compatibility with earlier Atmel Flash families.

FAQ

What is the maximum operating temperature range for the AT29C257-70JC-T?

The AT29C257-70JC-T is rated for commercial operation from 0°C to +70°C. Its PLCC-32 package and internal thermal design support reliable performance within this range under continuous read/write duty cycles. This specification is defined in the official Microchip datasheet revision 4-115 and confirmed by the "Ordering Information" table listing "Commercial (0° to 70°C)" for the -70JC suffix. The AT29C257-70JC-T does not support industrial (-40°C to +85°C) operation - that variant is designated AT29C257-70JI.

Does the AT29C257-70JC-T require a 12 V programming voltage?

No, the AT29C257-70JC-T operates with 5 V ± 5% only - no high-voltage programming supply is needed. All reprogramming commands (page program, chip erase, data protection enable/disable) are executed using standard 5 V logic levels applied to WE, CE, and address/data pins. This is explicitly stated in the "Features" section and verified in the "DC and AC Operating Range" table, which lists VCC = 5 V ± 5% for the -70JC variant. The AT29C257-70JC-T achieves this through on-chip charge pump circuitry integrated into its Flash cell design.

How is end-of-program detection implemented in the AT29C257-70JC-T?

The AT29C257-70JC-T supports two hardware-based end-of-program detection methods: DATA polling (monitoring I/O7 for complement-to-data transition) and Toggle Bit (observing I/O6 toggling state). Both methods operate without requiring precise timing loops in host firmware. During programming, reading any address returns toggling I/O6 or complemented I/O7 until completion, after which valid data appears. These mechanisms are fully documented in sections 4-112 and 4-113 of the AT29C257 datasheet and apply identically to the AT29C257-70JC-T.

Is the AT29C257-70JC-T pin-compatible with the AT29C512?

Yes, the AT29C257-70JC-T is pin-compatible with the AT29C512 in PLCC-32 packaging. Both share identical pin functions (A0–A14, I/O0–I/O7, CE, OE, WE, NC), same pinout order, and compatible DC/AC timing margins for read operations. This is explicitly confirmed in the "Features" list ("Pin-Compatible with AT29C010A and AT29C512 for Easy System Upgrades") and validated by matching "Pin Configurations" diagrams. However, firmware must account for the doubled memory depth (32K vs. 16K words) and updated page addressing (A6–A14 for 64-byte pages).

What is the endurance rating of the AT29C257-70JC-T?

The AT29C257-70JC-T has a typical endurance rating of more than 10,000 write/erase cycles per memory sector. This value is specified in the "Features" section and reiterated in the device description ("any sector can typically be written to in excess of 10,000 times"). Endurance is measured under standard 5 V operation with proper command sequencing and applies across the full commercial temperature range. The AT29C257-70JC-T maintains this rating without derating for page-program usage, as each 64-byte page erase/write cycle counts as one full endurance event.