5V (3 to 5A) switcher regulator (single chip) exist?

Thread Starter

GopherT

Joined Nov 23, 2012
8,012
Does anyone know of a stand-alone chip (no external inductor or diode required). Essentially the same as a 7805 linear but much less heat with switching setup.

Input is 8.4v lithium battery to the regulator and output 5V of 2 to 3 amps.

TO-220 or smaller package is preferred.
 

#12

Joined Nov 30, 2010
18,167
I have one that's good for half an amp, but its a small circuit board with the inductor and control chip soldered on it. It plugs into a place for a 7805, but it doesn't have the current you need and it isn't a single chip in a TO-220 package. I believe it is impossible to, "print" enough inductor on silicon to do what you asked for. Maybe there's a way to do it in PWM, but I haven't seen one.:(
 

dendad

Joined Feb 20, 2016
3,154
You will need an inductor to store the energy to make the switcher work. And some external capacitors. By "stand-alone chip" do you mean an IC or will a module work for you?
The LM2576 of the previous post needs the external parts.
There are a number of these sort of boards...
http://www.ebay.com.au/itm/LM2596S-Step-Down-Power-Supply-Module-DC-To-DC-Voltage-Regulator-Buck-Converter-/141806544502?hash=item2104542676:g:~QsAAOSwl9BWJfYR

Or you could go a bit more up-market with...
http://www.tracopower.com/products/browse-by-category/detail/dc-dc-converters/non-isolated-step-down-regulators/
I use some Traco TSR 1-2450 units in some of my products.
There are ways of adding these in parallel for more current by using eg, 0.1R series resisters on each output to balance the current.
But a n IC "chip" to do it alone is probably not an option.
 

Thread Starter

GopherT

Joined Nov 23, 2012
8,012
I have one that's good for half an amp, but its a small circuit board with the inductor and control chip soldered on it. It plugs into a place for a 7805, but it doesn't have the current you need and it isn't a single chip in a TO-220 package. I believe it is impossible to, "print" enough inductor on silicon to do what you asked for. Maybe there's a way to do it in PWM, but I haven't seen one.:(
Thanks, I should have been more clear about - module vs chip. Module would be fine. I'm just looking for super small - I was called into a project for robotics week competition at the last minute - they were drawing 3 Amps from a 7805 and it was shutting down. The bot is ok for high school. I just wanted to keep as much of their original as possible but, we will just reconfigure some other stuff to decrease current draw - bring the motors (70mA each) to unregulated and flash fewer IR emitters a time.

We 'll get it figured out. Thanks guys.
 

dendad

Joined Feb 20, 2016
3,154
They look really good!
And not to bad a price either. At least in x K quantities.
Mouser = $4.53 in lots of 250, on 6 weeks lead time.
 

crutschow

Joined Mar 14, 2008
23,742
It's able to get buy with a small inductor in the package since the PWM switching voltage is 2MHz and the required inductance value is inversely proportional to the switching frequency..
 

AnalogKid

Joined Aug 1, 2013
8,221
If the only problem with the original 7805 circuit is output current capability, what about adding 2 resistors and going with an LM350? No inductors expressed or implied, same mounting, and the heat load is exactly the same as what you have now with the 7805.

ak
 

Thread Starter

GopherT

Joined Nov 23, 2012
8,012
If the only problem with the original 7805 circuit is output current capability, what about adding 2 resistors and going with an LM350? No inductors expressed or implied, same mounting, and the heat load is exactly the same as what you have now with the 7805.

ak
Thank you! I completely forgot about the LM350 as a 3-pin TO-220 package. Sometimes I get knee deep in a problem and reasonable solutions are forgotten (especially with a panicked teacher and disappointed students looking over my shoulder). I just checked - I have two of the old TO-3 tin can packages and a nice unused TO-220 package buried in my parts boxes. The motors were re-routed to non-regulated last night (easy). The LM7805 was still overheating after about 45 seconds and causing some problems. Anyhow, I think a few resistors can be hung directly on the LM350 and the part can be inserted at a 90-degree angle to swap the output and adj pins in positions 2 and 3 (pin 3 (Adj) inserted in the middle position) - at least that is how envision it could fit onto the board for now.

Thanks again.
 

cmartinez

Joined Jan 17, 2007
6,621
FWIW, I've been using these for years. There are also 1 and 2 amp versions out there, for your consideration.

EDIT: hey... I think I might have just posted something useful... finally :)
 
Last edited:

Thread Starter

GopherT

Joined Nov 23, 2012
8,012
I thought you wanted a switching regulator. :confused:
A higher current linear regulator won't affect the heat problem.
I do not have a thermometer so I was not sure if the issue was over temp or over current. Hopefully it was over current and the 3A capabilities of the LM350 will take care of it. If not, it is a heat issue and we are back to the option of removing regulation for more of the project, or a switcher.



upload_2016-3-14_12-27-13.png
 

crutschow

Joined Mar 14, 2008
23,742
I do not have a thermometer so I was not sure if the issue was over temp or over current. Hopefully it was over current and the 3A capabilities of the LM350 will take care of it. If not, it is a heat issue and we are back to the option of removing regulation for more of the project, or a switcher.
The current limit in the LM78XX series works instantly.
If it takes 45s to limit the current, then it's a heat problem, not a current problem.
 
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