A long-time market leader in EPROM technology, Microchip offers 5V, 3V and Battery-Voltage™ (2.7V) EPROMs for a variety of applications. Microchip has one of the broadest ranges of one-time programmable (OTP) EPROMs, with densities ranging from 256-Kbits to 8-Mbits, speeds as fast as 45ns, and package options that including PDIP and PLCC. The devices are widely used for embedded program code storage in applications such as: cordless phones, video game players, printers, graphics cards, instrumentation, automotive, medical devices, telecommunications, networking, industrial control equipment, and hard disk drives.
Key Features:


  • Lower power — Microchip’s innovative design techniques provide fast speeds that rival 5V devices while retaining the low power consumption of a 3V power supply.
  • Two-line control — All devices feature two-line control (CE, OE) to give designers the flexibility to prevent bus contention.
  • Additional features — The AT27Cxxx and AT27LVxxx series both have additional features to ensure high quality and efficient product use, including Rapid Programming Algorithm and Integrated Product Identification Code.


Parallel EEPROM

Parallel EEPROM


Microchip is the world’s leading manufacturer of parallel EEPROM devices. Parallel EEPROMs enable stored data to be updated byte-by-byte or by full sector, providing design flexibility. The parallel interface devices offer faster read times than serial Interface protocols. Microchip provides a complete selection of densities (64-Kbit to 4-Mbit), operating voltages, and device packages. Microchip’s Battery Voltage™ (2.7V), low voltage (3V), and 5V devices are used extensively across a broad spectrum of products, including telecommunications, avionics, and military applications.


Key Features:


  • Save on components — The devices are accessed like a static RAM for the read or write cycle, without the need for external components.
  • Monolithic EEPROM — Microchip offers the only 4-Mbit monolithic parallel EEPROM (AT28C040) for use in military and commercial avionics applications.
  • Extra features — The devices offer extra features that include internal error correction, an optional software data protection mechanism, and space for device identification.


Memory Product Comparison
Serial and Parallel Flash

What is SuperFlash® Technology?


SuperFlash® technology is an innovative and versatile type of NOR Flash. SuperFlash technology uses a proprietary split-gate cell architecture which provides superior performance, data retention, and reliability over conventional stacked gate Flash.


SuperFlash® Technology Overview


Serial and parallel flash memory products are an excellent choice for applications requiring superior performance, excellent data retention and high reliability.




  • Broad offering of Serial SPI, SQI™, and Parallel NOR Flash products
  • Industry fastest program and erase times
  • Excellent reliability and data retention
  • Low power consumption
  • Small package offerings
  • Integrated security and memory protection features


Parallel vs. Serial SPI vs. Serial SQI™ Flash Devices


NOR Flash is available with either a serial or parallel bus interface. The choice of which bus to use is often dictated by the required data rates of the application as well as the amount of available I/O on the microcontroller and the board space available. With the ongoing demand for smaller and cheaper products, more designs are now being switched to a serial interface to reduce board space and component price.


Parallel   Serial SPI
Data Throughput       High           Medium
Pin Count                     32+            8+
Package Size                Large         Small
Power Consumption  Medium    Low
Cost                                High          Low

Today’s microcontrollers are often bond pad-limited. This means that the size of the die is limited by the space needed for bond pads rather than for the microcontroller gates / circuitry. Eliminating bond pads results in a smaller die, increasing the amount of die on a wafer and resulting in reduced cost per die. Additionally, more pins increase the assembly and packaging costs of both the microcontroller and the memory. This is why there has been a major shift from using parallel Flash to using serial Flash. However, switching to fewer pins means lower data throughput. In order to offset this, a quad I/O serial interface is being used in the latest serial devices to create SQI™ Flash devices.



Serial Flash
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Parallel Flash
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Serial EEPROMs


Microchip’s Serial EEPROM products are compatible with four serial bus types and support densities that range from 128 bits up to 1 Mbits. These bus types include the standard two wire I2C, three-wire Microwire, four wire SPI and the new single I/O, UNI/O® bus. As Microchip’s EEPROMs are compatible with the de facto industry standards, they can be used as drop-in replacements for competitor devices in most cases. By supporting a wide operating voltage range from 1.7 volts up to 5.5 volts and a wide temperature range from -40°C to 125°C almost all applications are supported. For new designs, Microchip’s value-added features include smaller footprints, lower power consumption, lower voltage levels (down to 1.5V), faster bus rates and higher endurance levels help ensure truly robust designs of the highest quality.
Microchip has been at the forefront of Serial EEPROM innovation – Along with ensuring highest quality products, today we offer a new family of single I/O UNI/O® EEPROM devices, the lowest voltage EEPROMs at 1.5V, the fastest bus speed on the SPI at 20 MHz and provide the industry’s lowest operating current which ensures lower power consumption. Microchip also recently launched a family of MAC address chips each of which are pre-programmed with unique EUI-48™ and EUI-64™ node addresses.


  • I²C Serial EEPROM Family
  • UNI/O® Serial EEPROM Family
  • Microwire Serial EEPROM Family
  • SPI Serial EEPROM Family
  • Single-Wire Serial EEPROM Family


MAC address chips products Parametric Search Serial EEPROM
Serial EERAM

Serial EERAM


EERAM combines the reliability of an EEPROM with the performance of an SRAM. It is a nonvolatile SRAM with a shadow EEPROM backup.


I²C™ Serial EERAM Family


4Kbit 47×04 

16Kbit 47×16

What is EERAM?


EERAM is a standalone SRAM memory with shadow EEPROM backup that helps retain the contents of the SRAM memory when system power is lost. The EERAM uses a small external capacitor to provide the energy needed to store the contents of the SRAM on to the EEPROM when system power is lost. Unlike NVSRAM, no external battery is needed. EERAM offers unlimited erase and write cycles to the memory and FRAM-like functionality at a fraction of the price.

How does EERAM Work?


The internal circuitry of the EERAM constantly monitors system power. Upon power-down or the inadvertent loss of system power below the trip voltage (VTRIP) the contents of the SRAM is securely transferred to the EEPROM array using energy stored in an external capacitor that is connected to the VCAP pin (pin 1). On power-up, the EERAM’s Auto-Store feature enables the contents of the EEPROM to be transferred back to the SRAM array when the system voltage goes back above VTRIP. The EERAM offers unlimited writes to the SRAM array and over 1M erase/write cycles to the EEPROM.


4Kbit 74×04
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16Kbit 47×16
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Serial SRAM

Serial SRAM


Serial SRAM is a standalone volatile memory that offers designers an easy and inexpensive way to add more RAM to their application. These 8-pin low power, high performance SRAM devices have unlimited endurance and zero write times, making them ideal for applications involving continuous data transfer, buffering, data logging, audio, video, internet, graphics, and other math and data-intensive functions. These devices are available from 64 Kbit up to 1 Mbit in density and support SPI, SDI and SQI™ bus modes.




Serial NVSRAM offers non-volatile RAM storage and is ideal for applications that need to write very often to the memory. This device is significantly lower cost than other non-volatile RAM devices and the data is backed using an external battery. This 8-pin, SPI device supports unlimited instantaneous writes to the memory array, making it ideal in applications such as meters, data loggers, data recorders, black boxes. These devices are available in 512 Kbits and 1 Mbit densities.


Getting Started with Serial SRAM




Microchip’s Serial SRAMs offer an easy and inexpensive way to add RAM to an application. With small, 8-pin packages and the SPI interface (which only requires 4 I/Os) these devices give designers added flexibility with regard to their RAM needs. The Serial NVSRAM devices offer the industry’s least expensive non-volatile SRAM or FRAM solution. These low power NVSRAM devices offer unlimited, instantaneous writes to the memory array while automatically backing up data in the event of a power shutdown using an external battery.


RAM Expansion Options:


There have traditionally been two ways to increase an application’s RAM:


  • Use a larger microcontroller. This option is less attractive if you must buy a larger, more expensive micro just to get more RAM.
  • Use external parallel RAM. But, parallel RAM uses large packages and typically requires at least 16-20 I/Os.


Serial SRAM now offers the flexibility to add RAM to a design without the disadvantages of a large micro or parallel RAM and uses the simple 4-pin SPI interface. These devices also offer improved performance with the SDI and SQI interface that offers up to a 4x improvement in data rates.


Serial SRAM Bus Modes – SPI, SDI and SQI


Serial SRAM devices are designed to work on the standard SPI interface at 20 MHz. On the 512 Kb, 1 Mb devices – the SO, SI (pin 2, pin 5) along with SIO2, SIO3 (pin 4, pin 7) are designed to work as bi-directional I/O pins.


In SQI mode, all 4 pins (pins 2, 4, 5, 7) are configured to read or write at any given time effectively ensuring 4 bits are transferred across the bus in a single clock cycle – this, in effect, multiplies the data rate by 4. So for example, a task that takes 40 clock cycles to complete in standard SPI mode can now be completed in 40/4 = 10 clock cycles. This feature is extremely useful when large amounts of data need to be transferred quickly.


In SDI Mode, only 2 of the pins are configured as bi-directional I/O pins (pin 2, pin 5), allowing you to get a maximum of 2x data rates. Our standard 512 Kb and 1 Mb SRAM devices can be used in SDI and SQI modes.


The same device in the same footprint can be used for SDI and SQI.



Serial SRAM Family


16Kbit 23×640
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256 Kbit 23×256
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512 Kbit 23xx512
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1 Mbit 23xx1024
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Serial NVSRAM Family


512 Kbit /23LCV512
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1 Mbit / 23LCV1024
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