Why do ICs require additional components instead of building them in?

Thread Starter

summersab

Joined Apr 8, 2010
146
So, stupid question from a non-EE, but why do certain ICs require additional components (many of which are fixed values) instead of building them in? For instance, I was recently using a MCP1702-1202E. It's a 1.2V 250mA voltage regulator. In the spec sheet, it states that 1.0 µF to 22 µF capacitors are required on the input and output pins, but a 1.0 µF capacitor is generally sufficient. I understand that for certain applications, this capacitor may need to be tweaked, but why couldn't there be a version of this IC that included the 1.0 µF capacitors instead of requiring that I solder on two extra pieces? There are a lot of other examples of this where I wonder why I have to add extra parts that have fairly standard values per the spec sheets, and it just makes me wonder (and causes my eye to twitch slightly). Other than, "Certain applications may require that these components be outside the norm," is there a good reason why there can't just be a "norm" version for standard applications?
 

Papabravo

Joined Feb 24, 2006
13,965
If all components could be fabricated on an IC they probably would be done that way. Sad to say capacitors and inductors are very hard to fabricate and take inordinate amounts of chip real estate. That is why they are external. Maybe you thought they were doing it just to annoy you, but I assure you that is not the case.
 

Thread Starter

summersab

Joined Apr 8, 2010
146
No, I wasn't assuming any conspiracy theories (e.g. they did it just to be obnoxious, it was done in order to increase the sales of component manufacturers in some sleazy deal, or they were helping out the PCB business by artificially requiring that engineers use more components and thus more space). I just really wondered WHY. I suppose your answer makes the most sense, but dang, I wish I could pop in a voltage regulator (or other component) that did its job without needing to look up spec sheets and order additional components. It just seems unnecessary.
 

crutschow

Joined Mar 14, 2008
25,131
They put everything on the chip that can be reasonably fabricated in the semiconductor process used to make the IC chip.
But the chip is the only thing they normally put inside the package.
Large capacitors, resistors, and inductors do not fall into that category, so they are added external to the chip package, since that's cheaper to do.
Certain analog devices, such as DACs and ADCs may have thin-film deposited resistors fabricated on the surface of the chip where many high accuracy (and possibly laser trimmed) resistors are needed, but that adds significant cost to the chip fabrication.
In theory they could add other parts inside the package but few would want to pay the large increase in cost that would entail.
 

RichardO

Joined May 4, 2013
2,271
It is done sometimes. The example that comes to mind is a part Maxim makes that takes their MAX232 RS-232 level shifter and puts the charge pump caps it needs in the IC package. This makes the part more expensive for a couple of reasons -- It requires a more expensive package with extra processing and the demand is lower for this specialized part.
 
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