STMicroelectronics M27C256B-70XF1

Overview

M27C256B-70XF1 from STMicroelectronics is a 256 Kbit (32K × 8) UV-erasable EPROM in FDIP28W ceramic window package, operating at 5V ±10%, with 70 ns access time, 30 mA active current, and 100 µA standby current. It features dual-line control (E/G), electronic signature (20h/8Dh), and supports programming at 12.75 V with 100 µs/word pulse width - used for firmware storage in legacy microprocessor systems requiring field-erasable non-volatility.

For engineers reviewing the M27C256B-70XF1 datasheet, M27C256B-70XF1 pinout, M27C256B-70XF1 application, or M27C256B-70XF1 equivalent, key selection criteria include UV erasure capability, TTL-compatible timing, two-line output enable architecture, A9-based electronic signature verification, and FDIP28W package compatibility with UV exposure fixtures.

Technical Context

The M27C256B-70XF1 implements a classic NMOS EPROM architecture with address latching via A0–A14 (15-bit), parallel 8-bit data I/O on Q0–Q7, and independent chip enable (E) and output enable (G) controls enabling low-power array partitioning. Its two-line control logic ensures bus contention avoidance and minimizes active power during partial memory access.

Programming requires precise 12.75 V ±0.25 V on VPP, 6.25 V ±0.25 V on VCC, and 11.5–12.5 V on A9 for electronic signature readout. Erasure relies on 2537 Å UV light at ≥15 W·s/cm² dose (15–20 min at 12,000 µW/cm²), with FDIP28W's quartz window enabling direct die exposure.

Key Specifications

Pinout & Package

FDIP28W (28-pin ceramic frit-seal DIP with UV-transparent window); dimensions: 36.9 mm × 15.2 mm × 4.3 mm (L × W × H), lead pitch 2.54 mm, window aperture centered over die.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AM27C256B-70DC, M27C256B-70XF1 provides field-erasable flexibility at the cost of ceramic packaging and UV handling requirements; versus AT27C256B-70PU, it offers tighter VPP control for enhanced programming yield in precision environments.

Availability

M27C256B-70XF1 is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy automotive ECU boot ROM, and military radio configuration memory requiring stable component supply across extended product lifecycles.

Supply support for M27C256B-70XF1 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in automotive, industrial, and power management ICs with vertical manufacturing capabilities.

The M27C256B belongs to ST's legacy EPROM product line, designed specifically for microprocessor-based systems requiring field-erasable non-volatile storage in harsh or long-lifecycle environments.

FAQ

What UV wavelength and exposure dose are required to fully erase M27C256B-70XF1?

Full erasure requires short-wave ultraviolet light at 2537 Å wavelength with a minimum integrated dose of 15 W·s/cm². Using a standard 12,000 µW/cm² UV lamp, the device must be placed within 2.5 cm of the source for 15–20 minutes. Room fluorescent lighting (3000–4000 Å) can cause partial erasure over months; opaque window labels are recommended for long-term storage.

Can M27C256B-70XF1 be programmed using a standard 5 V-only programmer?

No. Programming requires three distinct voltage rails: VCC = 6.25 V ±0.25 V, VPP = 12.75 V ±0.25 V, and A9 = 11.5–12.5 V for electronic signature verification. Standard 5 V programmers lack the regulated 12.75 V VPP supply and precise A9 biasing, risking incomplete programming or cell damage.

How does the two-line control (E and G) reduce power consumption in multi-chip memory systems?

E (Chip Enable) gates power to the entire array - when high, ICC drops to 100 µA regardless of address or data activity. G (Output Enable) only disables output drivers while keeping internal circuitry active. In multi-chip systems, E is decoded per device while G is shared, ensuring only one device draws 30 mA active current while others remain in ultra-low-power standby.

Is the FDIP28W package RoHS-compliant?

No. The FDIP28W package contains leaded solder (Pb-based frit seal) and is exempt from RoHS under Annex III (category 7a - high-melting temperature type solders). STMicroelectronics discontinued RoHS-compliant replacements for this package; alternatives require redesign to PLCC32 or TSOP28 OTP variants without UV capability.