Microchip’s recently developed UNI/O bus gives designers more flexibility when designing applications that require external memory. UNI/O EEPROMs only require one signal line to the microcontroller to carry both the clock and data signals thus creating a method to connect an EEPROM to a micro using only one I/O pin. Microcontroller I/O pins are valuable resources. By only requiring one of these pins, UNI/O EEPROMs free up other I/O pins to be used for value added features. This can increase system value using the same basic design. Or it might be possible to lower the system cost by moving to a smaller microcontroller. Another advantage of this bus is that these devices are available in very small 3 lead packages. One pin for clock and data and the other 2 pins for voltage and ground. This can mean a lower system cost and smaller designs.

Finally, UNI/O serial EEPROMs have been designed with advanced features such as a status register, advanced right protect options, and page rights and these devices have the standard EEPROM advantages that we talked about earlier. One million arrays right cycles, 1.8 to 5.5 volt operation, extended temperature options and low power. With that let’s take a look at Microchip’s complete serial EEPROM product line.

Here is our product road map. Lets first look at I2C products in the left most column. Note that the available densities are listed along the vertical Y axis. All products in this family start with a 24 prefix. It has a very wide density range from 128 bits to 1 megabit. The standard family has a maximum bus speed of 400 khertz and our larger densities have one megahertz versions. We also have several 1 and 2 kbit specialty products used for applications like computer monitors and dim memory sticks.

Next is our UNI/O EEPROM family which is available in 1 through 16 kbit options. It has a voltage range of 1.8 to 5.5 volts at a maximum speed of 100 khertz. Remember that these new products require only one connection to the master.

Now we will look at the microwire family. This family is also available in 1 through16 bit devices as limited by the microwire protocol. The part numbering schemes start with a 93 prefix and ends with a 46 for 1 one kbit, 56 for 2 kbit, and so forth. Although it has a narrow or density range microwire is faster than I2C and UNI/O parts at 3 megahertz. And remember this family has 4 signals, so it requires 4 micro I/Os as opposed to the 2 wire I2C bus and the single wire UNI/O bus.

Lastly here is the SPI product family which also requires 4 I/O pins. Like the I2C family, SPI has a very wide density range from 1 kbit to 1 megabit. But it also has much faster speeds up to 10 megahertz. Our 512 kbit and 1 megabit devices have a 20 megahertz maximum bus speed. But SPI speed and advanced data protection schemes do add to the dy size. So SPI devices are a bit more expensive that similar devices in the other protocols.

This slide shows some of the more common EEPROM packages. All package photos are correctly scaled relative to each other. Under each package is its name and its footprint dimensions. I have also noted the maximum density that can fit into each package. The most popular package is the 8 lead SOIC. It has a 5 by 6 millimeter footprint and can hold up to 512 kbits. The TSSOP and MSOP packages are also popular and are smaller and thinner than the SOIC. Each can hold up to 256 kbits.

Our smallest packages are next. The 2 by 2 mm SC70 package is our smallest option available in 1 and 2 kbit devices. The 3 by 3 mm SOT23 package in 3, 5 and 6 lead versions can hold up to16 kbits. The 2 by 3 mm TDFN package is also very small and is less than .8 mm thick making it an excellent choice for height limited applications. It can hold up to 64 kbits. Finally just about all our products are available in dy and wafer form.

So let’s compare the 4 buses. Here is a chart that shows some key features of each protocol. Density range, speed, security options, number of microcontroller I/O pins required, and package options. Under the heading for each bus, I have ranked that feature with one to three stars with 3 stars being the best.

As we have discussed earlier, I2C and SPI have the widest choices in density. All the way up to one megabit. So both these buses are in 3 stars in the density category. The microwire and UNI/O buses have a comparatively limited density range of 1 through 16 kbits. So they only get one star.

Next is speed. SPI has the fastest available bus speed followed by microwire. I2C and UNI/O bus are the slowest.

Now let’s look at security. The SPI and UNI/O protocols have the widest range of security options featuring both software and hardware data protection schemes. I2C features only hardware right protect and microwire has the fewest data protection options. The UNI/O bus is clearly the best in terms of I/O pins used since it only requires one microcontroller pin. I2C devices usually requires 2 I/Os and microwire and SPI parts require at least 4. I2C microwire and UNI/O bus also score well in the small package category. SPI parts require slightly larger packages in most densities. So what’s the best bus?

That of course depends on the needs of the application. If speed is the most important factor, SPI or microwire is the way to go. If speed at high density is most important microwire drops out and SPI is the clear choice. I2C is the most popular bus probably because of its wide density range, small packages and modest I/O requirements. And if you are pin limited or space limited, the UNI/O device may be the best answer.

As you can see there are a lot of choices. We offer the flexibility to optimize your design based on your application goals. Regardless of which protocol you choose it is fairly simple to make the connection to a microcontroller. Many micros have specific ports for each of the buses or general I/O ports can be used. We have a couple dozen app notes with code on our website explained how to connect devices of each bus type.

Let’s take a moment to recap our agenda. First we talked about Microchip’s long history of manufacturing non volatile memory. Then we talked about the general features of EEPROMs. Small packages, low power, high endurance, byte level flexibility, and operation under a wide range of temperature and voltage conditions. Then we compared the features and advantages of each of the 4 major buses including a look at our roadmap.

Now let’s take a look at the tools we offer for our memory products. Our major EEPROM tool is the MPLAB starter kit for serial EEPROM products. It is not just a memory programmer but a debugging tool. You can use the programming and read functions to write to or read from any Microchip device. The tool features byte, block and array functionality and you can transfer data to and from external files. It’s a very helpful and expensive debug tool. Our customers like its robustness, its user interface and its simplicity.

I have already talked about our second major tool, the total endurance modeling software. Recall it understanding endurance can be crucial. In this free downloadable software, you can enter application specific data to model the expected endurance event application. Finally we offer a large number of Verilog models on our website for download.

We are just about to the end of this seminar and we have really just hit the highlights of this product line. There is a lot more information available on our website. For more information on the different bus protocols, check out our product data sheets. These have excellent functional description including timing diagrams, command descriptions and electrical specifications. We also have many app notes that explain how to connect an EEPROM to a micro using all 4 buses. Finally we have more EEPROM web seminars including ones about our MPLAB starter kit, endurance with the tutorial on the total endurance software, small package options, usage recommendations for each bus and details of the new UNI/O product line. All these can be found on our memory home page at www.Microchip.com/memory. This wraps up today’s seminar.

In closing I would like to reiterate the following advantages of Microchip’s EEPROM product line. We offer a full line of serial EEPROM products in all 3 major bus types. And don’t forget our UNI/O line of single I/O EEPROM products. We offer competitive pricing. We understand that cost is an important component of product selection. All our EEPROM products have industry leading quality and endurance. We are also the industry leader in small packaging options including a broad range of products in the SOT23 and 2 by 3 DFN packages. Finally we understand how important delivery is to our customers. Because we own our own facs and our own test facility we have historically had excellent delivery performance especially during up cycles when memory product availability tends to become tight. Thanks for your time. Please take a look at some of the other excellent seminars we have prepared for you or take a look at some of our memory information on our website.

Watch or read:
Serial EEPROM Overview Part 1 of 2
UNI/O technology saves pins on low pin count microcontrollers