Single-function analog ICs solve problems without giving headaches

Article By : Bill Schweber

There’s a need for single-function analog ICs to crisply solve specific problems...

High levels of system functionality reached the analog-IC world many years ago. After all, why just have an A/D converter when you can instead have an IC with other needed functions such as sensor-signal conditioning, a programmable gain amplifier (PGA), memory for buffering or even data logging, various interfaces (SPI, I2C, others), and matched passives such as gain-setting resistors. It makes a lot of sense.

Nonetheless, there’s also a need for single-function analog ICs, predominately op amps or one of their many siblings such as instrumentation amplifiers (in amps) or isolation amplifiers (iso amps). There are many reasons for this diversity, but one is that no single op amp is ideal, and each one represents a tradeoff or compromise among many performance factors.

What I admire about many of these single-function analog ICs, however, is their ability to crisply solve a specific problem, do nothing else, and get out of the way. Interesting, there’s a digital-IC called “glue logic” that several years ago was often needed to make incompatible digital ICs work together by interposing a needed function such as a basic flip-flip or gate. The various 7400-series families of logic devices were widely used for this. Of course, the need for glue logic has decreased significantly as highly integrated digital ICs “glue” their many internal functions together as part of their design.

On the analog side, though, there’s still a role for small-scale, single-function ICs. For example, Maxim Integrated just released a set of ultra-tiny comparators – cousins of the op amp – in a variety of “flavors.” Their series of eight very similar nano power, four-bump comparators in ultra-tiny packages (just 0.73 mm × 0.73 mm) is certainly a good fit for this problem-solving role.

Why eight different comparators? Although each one is “just” a basic, no-frills device, each also has a different combination of inverting or noninverting inputs and open-drain or push-pull outputs, as shown in Figure 1. As a result, you can select the comparator that drops in and implements a planned-for and needed function, as well as one that can be squeezed in to remedy an unforeseen “oops” design situation. I can almost hear someone at a design-team meeting saying, “ummmm…we have a bit of a nasty problem with that signal between those two ICs” and someone else responding “hey, if we could just squeeze a comparator in there, we could knock that problem down easy.”

Maxim Integrated schematic drawings of tiny comparatorsFigure 1 The octet of tiny comparators offers different combination of input and output structures to make it easier to drop them in where needed without requiring support components. (Image source: Maxim Integrated)

The nice thing about simple, single-function ICs such as these (they are designated as MAX40002 through MAX40005 and MAX40012 through MAX40015) is that they don’t ask for a lot from the user. They are pretty much self-supporting, without the need for fancy I/O, level shifters, extra protection, sophisticated power requirements or sequencing, initialization software, or other factors that might otherwise make them hard to actually use. The goal of these analog components such as these is to get in there, solve the problem, and be quiet (figuratively and literally).

Have you ever used a basic analog part to fix or correct a circuit problem or system misunderstanding with relative ease? How did you realize what the solution was? Were you considered a “hero” afterwards, or was the problem too embarrassing to acknowledge?

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