M27V256 256 Kbit EPROM Technical Summary

Overview

The M27V256 is a low-voltage 256 Kbit (32K x 8) Erasable Programmable Read-Only Memory (EPROM) designed for applications requiring non-volatile storage. This component features a two-line control interface and operates at a reduced voltage, making it suitable for power-sensitive designs. The M27V256 offers reliable data retention and high-speed read access, making it ideal for embedded systems, firmware storage, and other applications where persistent memory is required.

With its industry-standard pinout and robust architecture, the M27V256 provides a cost-effective solution for legacy systems as well as modern designs requiring EPROM functionality. The device supports standard EPROM programming methods and can be erased via exposure to ultraviolet (UV) light, allowing for reprogramming during development cycles.

Key Features

• Memory Capacity: 256 Kbit organized as 32K x 8 bits
• Low Voltage Operation: Supports reduced voltage requirements for power-efficient designs
• Two-Line Control Interface: Simplified control scheme for easy integration
• High-Speed Access Time: Fast read operations for improved system performance
• UV Erasable: Can be fully erased with ultraviolet light for reprogramming
• Extended Temperature Range: Suitable for industrial applications
• Standard EPROM Programming: Compatible with conventional EPROM programmers
• Long Data Retention: Typically 10 years or more at specified conditions

Applications

The M27V256 is suitable for a wide range of applications including:

• Embedded system firmware storage
• Industrial control systems
• Automotive electronics
• Medical equipment
• Legacy system maintenance and upgrades
• Development and prototyping environments
• Educational electronics projects
• Telecommunications equipment

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (VCC): -0.6V to +7.0V
• Input Voltage: -0.6V to VCC + 0.6V
• Output Voltage: -0.6V to VCC + 0.6V
• Storage Temperature: -65°C to +150°C
• Operating Temperature: -40°C to +85°C (industrial grade)

DC Characteristics

• Supply Current (Active): 30 mA max @ 5 MHz
• Supply Current (Standby): 100 µA max
• Input Leakage Current: ±1 µA max
• Output Leakage Current: ±1 µA max
• Input Low Voltage: 0.8V max
• Input High Voltage: 2.0V min

AC Characteristics

• Address Access Time: 200 ns max
• Chip Enable Access Time: 200 ns max
• Output Enable Access Time: 100 ns max
• Read Cycle Time: 250 ns
• Write Pulse Width: 100 ms min (programming)

Functional Description

The M27V256 operates in three primary modes: read, standby, and programming. In read mode, the memory contents are accessed by providing a valid address and asserting the appropriate control signals. The standby mode significantly reduces power consumption when the device is not actively being accessed. Programming mode allows new data to be written to the memory cells using standard EPROM programming techniques.

The device features a two-line control interface consisting of Chip Enable (CE) and Output Enable (OE) signals. This simplified control scheme reduces system complexity while maintaining flexibility. The memory array is organized in a standard 32K x 8 configuration, with each byte individually addressable.

Programming and Erasure

The M27V256 supports standard EPROM programming methods. Programming is performed by applying a higher voltage (typically 12.5V) to the VPP pin while pulsing the control signals. Each byte must be programmed sequentially, with verification steps between programming pulses to ensure proper data integrity.

Erasure is accomplished by exposing the quartz window of the package to ultraviolet light with a wavelength of 2537 Å. Complete erasure typically requires 15-20 minutes of exposure to an UV lamp with an intensity of 12,000 µW/cm². After erasure, all bits will read as logic '1' (FFh).

Package Information

The M27V256 is available in several package options:

Standard Package Options

• PDIP (Plastic Dual In-line Package): 28-pin, 600 mil width, with transparent quartz window for UV erasure
• PLCC (Plastic Leaded Chip Carrier): 32-pin, square package with window
• TSOP (Thin Small Outline Package): 28-pin, surface mount option

Package Dimensions

• PDIP-28: 36.32mm x 15.24mm x 4.95mm (max)
• PLCC-32: 14.0mm x 14.0mm x 4.57mm (max)
• TSOP-28: 18.4mm x 8.1mm x 1.2mm (max)

Pin Configuration

The 28-pin PDIP package uses the following pinout:

• Pins A0-A14: Address inputs
• Pins O0-O7: Data outputs
• CE: Chip Enable (active low)
• OE: Output Enable (active low)
• VPP: Programming voltage input
• VCC: Power supply (5V ±10%)
• GND: Ground

Reliability and Quality

The M27V256 meets stringent quality and reliability standards:

• Endurance: Minimum 100 programming cycles
• Data Retention: 10 years minimum at 85°C
• ESD Protection: >2000V on all pins (Human Body Model)
• Latch-up Protection: >100 mA

Ordering Information

The device is available in several speed grades and temperature ranges. The complete ordering code includes:

• Device type (M27V256)
• Speed grade (e.g., -20 for 200 ns access time)
• Temperature range (I for industrial)
• Package type (e.g., P for PDIP, L for PLCC)

Example: M27V256-20PI indicates a 200 ns access time, industrial temperature range device in PDIP package.

Conclusion

The M27V256 256 Kbit EPROM provides a reliable, low-voltage memory solution for a wide range of applications. Its combination of standard EPROM functionality, simplified interface, and robust packaging options make it an excellent choice for both new designs and legacy system support. With its proven technology and dependable performance characteristics, the M27V256 continues to be a valuable component in the embedded systems landscape.