Over the years, I've come across chips that are invaluable for turning around systems quickly and with a minimum of hassle. One of the frustrating things I've dealt with is that finding these chips is difficult, and there's always neat new ones to hunt down. It's always amazing how easy the "right" IC will make an otherwise difficult job. Once you've got a pretty nice toolchest, it's suprising the types of tasks you can undertake and accomplish.

As I review and experiment with new chips, check back here to see what's new.

Have a favorite IC application? Send it along!

Dallas Semiconductor DS1302 Real Time Clock (RTC) (pdf)

Real time clocks are useful for timestamping data collection and scheduling events on a periodic basis. A lot of micros have built in support for RTC functionality, but few have all the features of a dedicated real time clock - leap year skipping, battery backup, capacitor charging support, and calendering. I've found the DS1302 to be a great little IC, available in convenient 8-DIP and 8-SOIC packages. It works well combined with the Panasonic series #XX gold backup capacitors. You can find a set of library functions for working with this IC included with the xMega board.

Maxim MAX7219 Display Driver (pdf)

This is a great LED display driving solution. I prefer to use 7-segment displays where possible for their low cost and high brightness and readability. They come with more software overhead if you are managing your brightness and update levels with the microcontroller directly.

The MAX7219 deals with all of these complexities and even removes the need for resistors; all you need is a bypass capacitor and a single feedback resistor to set the maximum (peak) current to the LED. Communication is easy through and SPI interface. Another neat feature is a built in cascading function; you can drive 16 7-segments with a single enable line and address them all directly with two IC's chained together.

Maxim MAX479 Precision Opamp (pdf)

The MAX479 is a great single-supply precision amplifier. I've used it in a number of thermocouple interface applications and instrument preamplifier configurations. Even configured in a single stage, this chip delivered great performance for amplifying near-amblient thermocouple signals. It's only drawback is price, but you knew that was coming, didn't you?

Burr-Brown OPA4344 Precision Opamp (pdf)

This quad opamp is a little more expensive than a standard LM324, but offers great performance from a single supply and operates to both supply rails. It makes a great buffer or preamplifer chip when 0-5V performance range is needed on a +5V supply.

LM324 General-Purpose Single Supply Opamp (pdf)

Not much to say about this staple IC; They cost a quarter, run from single or dual supplies, are stable to 30V, and can drive to the 0V rail. Their only disadvantage is they're limited to their positive rail - 1.5V. If you're working with the atmel chip with the analog reference in the 2.56V mode, they're a great low-cost signal buffering IC. Texas Instruments makes an especially robust version of the 324 that has 2kV ESD protection built in. (LM324K)

If you're serious about experimenting with opamps, or do any amount of data acquisition or measurement, buy a rail of these. At $0.25/IC, available in 14-DIP and a variety of other packagers, they're a great bargin.

LM358 General-Purpose Single Supply Opamp (pdf)

The primary advantage I've found to this IC is it's widely available in 8-DIP for prototyping smaller circuits, and shares a low cost and wide production base with the LM324.

LM1815 Variable Reluctance Sensing IC (pdf)

Variable reluctance sensors are widely used in the automotive world for doing engine timing from a toothed wheel - it provides a very robust, accurate way to determine things like crankshaft rotation angle from top dead center. They're also usd to detect zero crossings, as tachometers and in general position sensing applications.

The difficulty is in cleaning up the the signal to where's it's easily interpreted by a micro. The LM1815 solves this problem completely - connect up your sensor, and get a clean interrupt ready pulse back.

Maxim MAX233 / Analog Devices ADM233 Level Tranciever (pdf)

Everyone is framiliar with the MAX232 level tranciever. The problem is it requires external 1uF capacitors and can eat up a a lot of board space. The solution to that is the Max233; there's a second-source part from Analog Devices, the ADM233 that is lower cost. I've found the MAX233 to be a great preformer, working in very noisy environments where other chips gave up. It's nicely matched to prototype micro projects where a serial link is needed.

4N25 Optoisolator IC (pdf)

Optoisloating is a very handy trick if you need to work with nasty signals. It's an efficient way to provide isolation in conjunction with a small DC/DC converter as well. 4N25 chips have an LED on one side, and an exposed BJT on the other. Adding a pull-up resistor gives you your logic signal out. They're inexpensive vailable in convenient 6-DIP packages.

Sharp PC815 Photodarlington IC (pdf)

If you need a little more gain from your optoisolator, these are the ticket. The only problem is the added gain comes at the expense of speed. They're available in 1, 2, 3, and 4 optoisolator configurations, PC815, PC825, PC835 and PC845 respectively.

ULN2003A Darlington Array (pdf)

Sometimes you find a chip you keep finding new applications for. This is one of my favorites; the ULN2003 packs 7 darlington transistors with built-in base resistors and a protection diode. This allows the chip to be directly interfaced to TTL logic, no muss, no fuss. I've used this guy to build LED display driver arrays, general purpose open collector outputs, and driving arrays of mechanical relays. The fact it's less than a dollar makes it even better.

LM34 Temperature Sensing IC (pdf)

Put 5V in, get 10mV/F out. There's not much more to say about this guy. You get better resolution on the farenheit scale than celcius, so there's no advantage to using it's LM35 version if you're feeding the data into a micro. If you're working with lower-resolution ADCs (8, 10 bit), use a single supply opamp to apply a gain of two or three to increase your effective resolution.

Something else to keep in mind - while this chip needs to be driven with a bipolar supply to read negative voltages, you can read down to 0F with a single supply. This will get you well below freezing, which is fine for most applications.

LM19 Temperature Sensing IC (pdf)

There's one big problem with the LM34 style sensors, and that's they don't like to read negative voltages on a single supply. Luckily, National Semiconductor has solved that one for us: The LM19 reports the temperature in degrees Kelvin! Since nothing can approach absolute zero, or zero Kelvin, this is a pretty clever hack. It does lose a little accuracy over the LM34, but I've used this sensor in several outdoor applications without any problems.

AD595/AD594 Thermocouple Interface ICs (pdf)

It goes without saying that engineers love thermocouples. They're very inexpensive sensing elements, they're available in all sizes from micro-fine wire to thick pads. They can read room temperature or 1200 degrees celcius. Like most things in engineering, it's never that easy though. For large temperature readings, it's very easy to get good results with a precision opamp and a pile of gain. For smaller signals, that can require some patience, and often you want cold junction compensation.

The AD594/595 solve all those problems by taking a thermocouple input, either type J or K depending on the IC - type T is supported with a known error - and turning it into a LM34 style 10mV per degree output. The only thing to remember is that in order to read below zero, the IC requires that you drive it with a negative voltage - and this will then require an offset to be added in order to sample with your ADC.

TIP122/125 Darlington Transistors (pdf)

When I was in university, I was taught BJT's were an old technology and MOSFETs were the way of world. Then I got out into industry and started working in industrial, nasty environments and learned exactly how sensitive MOSFETs can be to ESD, load spikes, and other transient nastiness.

If you need a IC that will drive several amps at low frequency, this chip in a TO-220 package is almost bulletproof. Just remember to add a kickback protection diode if working with inductive loads, e.g. relay drivers. It's even inexpensive - around $0.50/pc.