27256

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M27256 - 256K (32K x 8) UV Erasable PROM

Overview

The M27256 is a high-performance 262,144-bit ultraviolet (UV) erasable and electrically programmable read-only memory (EPROM) organized as 32K x 8 bits. This component is designed for applications requiring non-volatile memory storage with the flexibility of reprogrammability. The M27256 features a single 5V power supply, making it compatible with a wide range of digital systems. Its UV erase capability allows the device to be reset and reprogrammed multiple times, providing versatility during development and testing phases.

The M27256 is housed in a durable ceramic or plastic package with a transparent quartz window, enabling UV exposure for erasure. It offers fast access times, low power consumption, and high reliability, making it suitable for industrial, automotive, and consumer electronics applications.

Features

• High-Capacity Storage: 262,144-bit memory organized as 32,768 words x 8 bits.
• Single 5V Power Supply: Simplifies system design and reduces power requirements.
• UV Erasable: Full memory array can be erased via UV light exposure for reprogramming.
• Fast Access Time: Available in speed grades as low as 150ns, ensuring compatibility with high-speed microprocessors.
• Low Power Consumption: Active current of 30mA (typical) and standby current of 100μA (max), enhancing energy efficiency.
• Programmable Control: Features a two-line control (CE and OE) for easy interfacing with microprocessors.
• Wide Operating Temperature Range: Industrial-grade versions support -40°C to +85°C.
• Durable Packaging: Available in 28-pin ceramic or plastic DIP with quartz window for UV erasure.
• High Reliability: Endurance of at least 1,000 program/erase cycles.

Applications

The M27256 is widely used in systems requiring firmware storage, code updates, and non-volatile data retention. Key applications include:

• Embedded Systems: Firmware storage for microcontrollers and microprocessors.
• Industrial Control: Program storage for PLCs, motor controllers, and automation systems.
• Automotive Electronics: Engine control units (ECUs) and infotainment systems.
• Consumer Electronics: BIOS storage in computers, gaming consoles, and set-top boxes.
• Telecommunications: Code storage in routers, switches, and base stations.
• Legacy Systems: Upgradable memory for retro computing and vintage hardware.

Electrical Characteristics

The M27256 operates under the following electrical specifications:

• Supply Voltage (V_CC): 5V ±10%
• Active Current (I_CC): 30mA (typical), 100mA (max)
• Standby Current (I_SB): 100μA (max)
• Input/Output Voltage Levels: TTL-compatible (V_IL = 0.8V max, V_IH = 2.0V min)
• Output Drive Capability: 2.0mA (min) at logic high, 4.2mA (min) at logic low
• Access Time (t_ACC): Ranges from 150ns to 250ns depending on speed grade
• Chip Enable to Output Delay (t_CE): 70ns (max)
• Output Enable to Output Delay (t_OE): 40ns (max)

Programming and Erasure

The M27256 supports the following programming and erasure procedures:

• Programming Voltage (V_PP): 12.5V (required during programming)
• Programming Algorithm: Byte-by-byte programming with 50ms pulses per byte.
• UV Erasure: Requires exposure to UV light (2537Å wavelength) at 15W-sec/cm² dosage. Full erasure typically takes 15-20 minutes under a UV lamp.
• Data Retention: Guaranteed for 10 years at 55°C after programming.

Package Information

The M27256 is available in multiple package options:

• 28-Pin Ceramic DIP (Cerdip): Windowed package for UV erasure (JEDEC standard).
• 28-Pin Plastic DIP (PDIP): Cost-effective option with UV window (less common).
• 32-Pin PLCC: Surface-mount variant (less common for EPROMs).

Pinout Configuration (28-Pin DIP):

• Pins A0-A14: Address inputs (15 lines for 32K addressing).
• Pins O0-O7: Data outputs (tri-state during programming).
• CE (Pin 20): Chip Enable (active low).
• OE (Pin 22): Output Enable (active low).
• V_PP (Pin 1): Programming voltage (12.5V).
• V_CC (Pin 28): +5V power supply.
• GND (Pin 14): Ground.

Conclusion

The M27256 is a versatile and reliable UV-erasable EPROM, offering a balance of performance, density, and reprogrammability. Its compatibility with 5V systems, low power consumption, and robust packaging make it a preferred choice for legacy and embedded applications. Engineers can leverage its fast access times and ease of integration for firmware storage in demanding environments.

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