Im in need of a 5V regulator that must be rated for 3A. Also, price is a major consideration. Is the LT1085CT my best option? These are a bit pricey and I don't need the adjustable feature. Is there anything else?
When dealing with 3A i would definitely go for a switching regulator
Okay, maybe if I explain my goal in this project that will help. I want to power an arduino as well as 2 USB ports for charging two iPhones. The led display and arduino consume about 200mA while the two iPhones will consume 2A. (total 2.2A, i can do math!)
At first I used a 5V 4A wall wort. After plugging in one iPhone, there was enough of a voltage drop that the second would not charge.
I switched it to a 9V 1.5A wall wort coupled to a LM7805 5V regulator (just to test for a voltage drop) and everything works great. No voltage drop. In theory, once I get a 2.5A+ supply, It should be fine to charge two phones and the circuit. But the LM7805 is only rated for 1.5A.
Is that big switching regulator and a 9V 2.5A supply the best way to power all this?
If you need Linear Regulator with 3A, you may try LT1085
but charging iPhone need higher then 5V, like 5.25V,
for high current like 3A, i would suggest go for a switching regulator.
Seems that the issue is lack of current supplied..
Once you have a supply good enough (be a switchmode ps) or a transformer step down supply.
Then ideally you need a voltage around 7-8v / 3amps, then an adj sm regulator to get your final 5v supply to your usb, but you could as easily use a power transistor and a 0805 .
The local Dollar Tree store has 1A USB car chargers like below for $1.
The local Dollar Tree store has 1A USB car chargers like below for $1.
Thanks, but how will this solve anything.
So I guess it is best to use a switching regulator. Which one to use though? Where can I learn more about a wiring schematic?
So I guess it is best to use a switching regulator. Which one to use though?
I usually start by flipping through my Jameco catalog. Then, maybe Digikey.
The 1st possibiility I found was the [u]LM2576[/u].
Where can I learn more about a wiring schematic?
After you've identified a potential regulator chip. The manufacturer's data sheet will give you recommended circuits.
At first I used a 5V 4A wall wort. After plugging in one iPhone, there was enough of a voltage drop that the second would not charge.
You might need to research the charging requirements for an iPhone. You might need separate regulators (or charging circuits) so that one phone can't drag-down the other voltages. But, I don't think that should happen with an iPhone... I think as standard USB2 port can only supply 500mA, so there might be something "funny" going on.
But the LM7805 is only rated for 1.5A.
With ANY linear voltage regulator, you also have to consider the POWER dissipation (the voltage dropped across the regulator X the current). I'm not sure what the power rating for the 7805 is, but you'd need a heatsink at 1.5A, and you'd have to make sure the voltage drop is not too high. When you get up to around 1A, I agree with what everybody else is saying... Consider a switching regulator.
Has anyone, ever, under any circumstances, gotten 1.5A out of a 7805? 
I put my linear regulator to switching regulator threshold at around 300mA. Any higher than that and it's just more trouble than it's worth.
Still, a few solid amps is no picnic even for switching regulators. If you want to charge tablets, you need around 2A per device. That's a pretty stout load if you're charging two at once. You'll need external switching transistors for most regulators / controllers, big inductors, and good layout. Not an easy task for a beginner, but doable.
Thanks, but how will this solve anything.
The USB car charger charges my cell phone, but it is apparently not a 2A power hog.
edit: iPhone chargers
Have look at these:
as well as the ones listed under "Customers Who Viewed This Item Also Viewed" half way down these web pages.