27C256B Technical Summary

27C256B - 256 Kbit (32K x 8) UV Erasable and Electrically Programmable Read-Only Memory (EPROM)

Overview

The M27C256B is a high-performance 256 Kbit EPROM organized as 32K x 8 bits. This UV erasable and electrically programmable read-only memory is designed for applications requiring non-volatile memory storage with the flexibility of field programmability. The device features a single 5V power supply and is housed in a standard 28-pin package, making it compatible with a wide range of systems.

With access times as fast as 45ns, the M27C256B is suitable for high-speed microprocessor-based systems. The device offers low power consumption in both active and standby modes, making it ideal for power-sensitive applications. The memory array can be erased by exposure to ultraviolet light, allowing the device to be reprogrammed for design iterations or firmware updates.

Key Features

High-density storage: 256 Kbit (32,768 words x 8 bits) organization
Single power supply: 5V ±10% operation
Fast access time: 45ns, 55ns, 70ns, and 90ns speed grades available
Low power consumption:
- 30mA active current (typical)
- 100μA standby current (typical)
Programmable: Electrically programmable with 12.75V programming voltage
Erasable: UV erasable with 15-20 minutes exposure to UV light
Wide temperature range: Commercial (0°C to +70°C) and Industrial (-40°C to +85°C) versions available
CMOS technology: For improved noise immunity and lower power consumption
Three-state outputs: For direct connection to system bus
Program inhibit: Allows programming of individual bytes
Program verification: Built-in functionality for programming verification

Applications

The M27C256B is suitable for a wide range of applications requiring non-volatile memory storage with the ability to update firmware or data in the field. Typical applications include:

Microcontroller-based systems
Industrial control systems
Automotive electronics
Medical equipment
Telecommunications equipment
Computer peripherals
Embedded systems
Firmware storage for BIOS and other system software
Game cartridges and arcade machines
Legacy system maintenance and repair

Electrical Characteristics

Absolute Maximum Ratings

Supply Voltage (VCC): -0.6V to +7.0V
Programming Voltage (VPP): -0.6V to +14.0V
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:
- Commercial: 0°C to +70°C
- Industrial: -40°C to +85°C

DC Characteristics (TA = 25°C, VCC = 5V ±10%)

Input Leakage Current (II): ±1.0μA (max)
Output Leakage Current (IOZ): ±1.0μA (max)
Standby Current (ISB): 100μA (max)
Operating Current (ICC): 30mA (max at 5MHz)
Input Low Voltage (VIL): 0.8V (max)
Input High Voltage (VIH): 2.0V (min)
Output Low Voltage (VOL): 0.45V (max at IOL = 2.1mA)
Output High Voltage (VOH): 2.4V (min at IOH = -400μA)

AC Characteristics

Address Access Time (tAA): 45ns, 55ns, 70ns, or 90ns (depending on speed grade)
Chip Enable Access Time (tACE): 45ns, 55ns, 70ns, or 90ns
Output Enable Access Time (tOE): 20ns (max)
Chip Enable to Output in Low-Z (tLZ): 0ns (min)
Chip Disable to Output in High-Z (tHZ): 25ns (max)
Output Enable to Output in Low-Z (tOLZ): 0ns (min)
Output Disable to Output in High-Z (tOHZ): 25ns (max)