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Voltage Regulator in an IC form-factor?

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Hippogriff

Hippogriff

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Hi,

Some time ago I started a thread on here wanting to know if there was an 'alternative' to transistors... by that I really meant, a different package, and I ended up finding out about the IC form factor. I was really pleased as I was able to replace 3 resistors and 3 transistors with a single IC that did the same job for me.

I am now wondering if I can do the same with a voltage regulator and the two capacitors I need to get 12v down to 5v. At the moment, I'm using the three pronged 7805 and two little capacitors with some wires... I was curious, is there an IC package of this entire thing... probably at least a 6 pin thing... that would take in 12v on one pin and push out 5v on another pin that can then go to the power pin of my PIC?

That would be cool... I'd remove several more components and lots of soldering effort. Not been able to find anything that fits the bill yet, though, all Google returns are the 3 pronged form factors with the big metal bit on top that acts as a heatsink (I think) and, I understand, that is maybe why what I'm looking for doesn't even exist.
 
You can check out the NTE923D it's a dip package adjustable regulator, but, you'll need support components to configure it.
You didn't mention how much current you need, the 923 can be configured with a pass transistor for high current if needed.
 
Ah, the NTE923D is something akin to what I think I'm looking for - thanks. That appears a very 'smart' device, though. Is there something you might class as a bit dumb, that just takes in a voltage, say 12 or more, and outputs a steady 5v to power a PIC?

Current-wise, it'll not be much, as the RGB LED strip I'll be controlling from the PIC will be connected straight to the 12v coming in from the power adapter anyway.

I've kept searching and found this...

**broken link removed**

...but it still seems to need a chunk of external components to get it doing its work.

P.S. - learned a new term, "buck converter", nice.
 
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I am confusing myself a little now... I've seen quite a few 8 pin-DIP options, fixed 5v output, look like what I want. But they seem to require 4 external components to just do a step down to 5v. My idea was that I wanted to move to an IC to reduce the component count... but with a 7805 tripod thing I only have 2 external components, i.e. 2 little capacitors.

Linear Technology, Micrel, National Semiconductor, Maxim etc. all seem to play in this space, but all their products appear essentially identical.

The reason why I'm confusing myself is that their datasheets seem to make a big deal out of the fact that only 4 external components are required, as though it's some major selling point. They see this (or are putting it across) as a plus, when I see it as a bit of a minus... I don't want to solder 8 pins and 4 external components.
 
A 7805 with 2 capacitors is as few components as you can get, Capacitors are too large to fit in an IC. The other regulators you were looking at are switching regulators, They are much more efficiant but require more components. Only 4 extra components is pretty good !
 
Yeah, it's not the size per se... it's the fact that I like things to be neat and 7805s with capacitors are not neat. Just like my previous comments re. transistors. I am more concerned about neatness and simplicity (i.e. reducing the number of discrete components that all need soldering) than cost in this instance, so if there was a solution and it was a few Quid, I might go for it. However, as Brevor says, I might be looking for something that doesn't exist - I will go and check out the MAX667 right now, though.
 
Large capacitors defy integration on a chip, thus they are almost always external to the IC needing them.

The thing to understand is that IC's are normally built on a single chip of silicon. If it can't be integrated on the chip, then it has to be external to the chip. The only time such devices are put internal to the package are in Hybrid type devices, and those are usually significantly more bulky and expensive then ICs. They are normally only used in expense, hi-rel systems such as military or space, although I believe there are a few, relatively low-cost, hybrid switching regulators that are built for commercial use.
 
The MAX667 looks kinda cool... tho' it's not obvious where to buy it from at the moment... Google provides me loads of links about what it is, but not where to buy it from... will recommence the search tomorrow from the usual suspects.
 
Quick update - I just purchased 4 x ADP667AN / ADP667 pin compatible with MAX667 from a Polish eBayer. Pretty cheap, seemingly, worth a punt... hope it works out.

The datasheet for the ADP667 still reckons "It can be used to give a fixed +5V output with no additional external components..." but I reckon there's still a need for a 10µF capacitor, even if I'm going with the +5V, as shown on the first page.

ADP667AN pdf, ADP667AN description, ADP667AN datasheets, ADP667AN view ::: ALLDATASHEET :::

It'd be cool if I didn't even need that...
 
If you don't need much current for the 5V, look at a 78L05. Same foot print as a small T0-93 transistor package. But, you will still need those two pesky external caps. How about posting your schematic, and letting the experts here make recommendations based on your particular circuit.

Ken
 
OK, my four ADP667s arrived today from a Polish eBayer... took a while, but they were cheap. I've been poring over the datasheet - I want the simplest configuration it seems - a steady 5v output from its OUT (pin 2)... I'll be using a power supply of 12v into IN (pin 8) and I'm not doing anything complicated so GND (pin 4), SHDN (pin 5) and SET (pin 6) can all be connected to ground. OUT (pin 2) can go to a capacitor.

**broken link removed**

Now, what I'm perplexed by is whether my IN (pin 8) also needs to connect to ground, via a capacitor? That diagram seems to infer it does... but I'm not sure what rating of capacitor, or whether it's even true that it is needed. Some of the other diagrams, i.e. figure 3 on the same page of the datasheet, don't show that on the IN pin - they just show a source voltage coming in, nothing more.

I wonder if anyone knows whether I can get away using this ADP667, to provide 5v, with just the one 10µF capacitor on the OUT pin (pin 2)? Also, does the IN pin (pin 8) need to be provided with 12v from the source and then go straight to 0v too?

Any guidance appreciated before I break these. ;)
 
2 external caps and a 3 terminal regulator sounds about as low-component-count as you're going to get. you may be a neat freak, but some passive components are required for EVERYTHING. also be aware that neatness and circuit performance don't always go hand in hand. for instance a power supply for an audio amp can be nicely and neatly laid out, but must have a single point ground, which meamd a nice neat straight ground buss is out of the question. the higher in frequency, the more neatness is a hindrance. SMT components help the situation some, but if you look at the DSP board on a modern AV receiver or the main board for a blu-ray player, you'll see that the closer you are to the CPU chip, the higher the component density, especially capacitors. even if you were able to get useful sized of capacitors mounter inside a chip, you still need some on the outside to cancel lead inductances. also be aware that because a 3-terminal regulator uses an internal op amp, the output impedance of the regulator rises with frequency, and so as frequency rises, the regulator's ability to deal with noise is reduced. this is the reason the caps are required.
 
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Sure is interesting commentary... ;) ...but, you've got to admit, it's not really that much direct help for my question about the ADP667 and 5v.
 
Hippogriff said:
OK, my four ADP667s arrived today from a Polish eBayer... took a while, but they were cheap. I've been poring over the datasheet - I want the simplest configuration it seems - a steady 5v output from its OUT (pin 2)... I'll be using a power supply of 12v into IN (pin 8) and I'm not doing anything complicated so GND (pin 4), SHDN (pin 5) and SET (pin 6) can all be connected to ground. OUT (pin 2) can go to a capacitor.

**broken link removed**

Now, what I'm perplexed by is whether my IN (pin 8) also needs to connect to ground, via a capacitor? That diagram seems to infer it does... but I'm not sure what rating of capacitor, or whether it's even true that it is needed. Some of the other diagrams, i.e. figure 3 on the same page of the datasheet, don't show that on the IN pin - they just show a source voltage coming in, nothing more.

I wonder if anyone knows whether I can get away using this ADP667, to provide 5v, with just the one 10µF capacitor on the OUT pin (pin 2)? Also, does the IN pin (pin 8) need to be provided with 12v from the source and then go straight to 0v too?

Any guidance appreciated before I break these. ;)
Click to expand...

what you're seeing on the input is a battery symbol, not a capacitor.
 
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