DC-DC Converters - Sources?

timmeh87 · Post by **timmeh87** » Wed Mar 08, 2006 5:39 pm

ok. i think we need to go over the samples thing again:

TI makes many different kinds of products. among these there are DC-DC converters. the ones TI makes come in many shapes an sizes. some of them are preassembled, and ready to hook into your circuit with three pins. others come as a small microchip that you are responsible for for making a circuit board for. if you dont have at least 15 hours of free time on your hands and a few years electronics background, dont even try to use the "harder" ones.

X-factor, im assuming you got that one based on something i said to you or someone else in an earlier thread (i foget exactly where). i warned people that that one was very difficult to implement, it is the kind that you have to make your own circuit board for. also, i mentioned it in a post where lithium batteries were being discussed. this converter, as it states on the main page that you order it from, cannot handle more than 5.5v input. my reccomendation to you is to hang onto it incase you ever might need it 10 years down the road, but order one of the easier ones for you project.

everyone: how do you tell what a part is and what it does? READ THE DATASHEET. my brother did it, xfactor did it, and i bet a lot of other kids are doing it: ordering parts from TI without even knowing what they are, or how to use them. PLEASE read the datasheet, and fully understand what you are ordering. know what inputs and outputs it requires, and what external parts you will need for it. know what each pin does, and what you will connect it to. think about how you will use it. basically act like you actually have to pay for it. if at any point you realize that it wont work for you, then dont order it in the first place. i really, really dont want TI to stop giving out samples. another electronics company recently started charging shipping on samples because too many orders were being placed.

im not specifically mad at anyone here (dont worry xfactor, we're cool). im just very concerned about the future freeness of my samples.

Post by **Gamelver** » Wed Mar 08, 2006 7:29 pm

lol, looking out for number one, eh

?

seriously, though, it is important to read the datasheet first!

XFactor · Post by **XFactor** » Wed Mar 08, 2006 7:43 pm

I get what you mean timmeh. We're cool; i guess i never knew how sensative TI would be to this sort of thing (although i have only ordered one part, i get how they would cease free shipment given a huge influx of orders). I love overnight shipment too, very very much......

G-force, not to sound redundant but i want to get this right: i looked up how much the PT78HT233V was in stock and it was zero. Can i go with the PT78HT233H and still have it just as easy? What are the "tabs" your refering to with the V model?

S q u e e ! · Post by **S q u e e !** » Wed Mar 08, 2006 7:56 pm

The "tabs" are two prongs that come out of the back to help it mount to the circuit board.

XFactor · Post by **XFactor** » Wed Mar 08, 2006 8:55 pm

Is this the right cap to put on the output?
http://www.weisd.com/store2/NTENEV100M10BA-B.html

Are some capacitors more efficient or is that not a factor here?

S q u e e ! · Post by **S q u e e !** » Wed Mar 08, 2006 9:25 pm

Not if your battery is above 10v

daguuy · Post by **daguuy** » Wed Mar 08, 2006 9:34 pm

not if the output is above 10v

it'll work. caps just hold a charge/get rid of ripples and stuff. there's no efficiency invlolved (i think)

XFactor · Post by **XFactor** » Wed Mar 08, 2006 9:35 pm

No, it'll be a 7.4v so i think i'm good here. Only i don't think i'll order off this website since shipping is like $8 and the unit itself costs like $0.23

I understand that this converter is used to "step down" (hence the name) the voltage to 3.3v to run on the second line. However, which conveter would you use to power your 12v line? Is it more complicated to manufacture?

daguuy · Post by **daguuy** » Wed Mar 08, 2006 9:38 pm

the 12v line already has a regulator (7805) that steps it down to 5v and works with as low as 7.2v

XFactor · Post by **XFactor** » Wed Mar 08, 2006 10:11 pm

Sweet. All I need to do now is get the converter i just ordered as well as a battery. I am thinking of one that has 4800mAH which should be plenty for 2.5 hours; however, i am also putting (because i want to keep the case slim, i am getting smaller heatsinks) a fan into the unit, so i was also considering a 6000mAH battery to compensate for the energy lost by the fan.

BTW, is the LED mod really needed? I have a PSone screen and i didn't know if this (the mod) was just to make it look pimp.

Post by **marshallh** » Wed Mar 08, 2006 10:19 pm

The LED mod really helps to save power. The screen's draw goes down from 750mA to 350mA, a savings of 500 milliamperes. That's pretty significant in a portable.

XFactor · Post by **XFactor** » Wed Mar 08, 2006 10:43 pm

I am trying to understand: the mod lowers the brightness of the screen while at the same time providing a more efficient (and power saving) lighting source (from the LEDs)? Do the LEDs act as the backlight for the screen because it's brightness has been lowered?

daguuy · Post by **daguuy** » Wed Mar 08, 2006 10:45 pm

it's really simple. the old backlight took a ton of power but was really bright. the LED mod replaces the powerhog light with some more efficient LEDs, lowering the brightness a bit but raising the battery life a lot

Aquador · Post by **Aquador** » Thu Mar 09, 2006 6:12 pm

Ok, I got the converter, now, even though it says that the minimum input voltage is 9 in the datasheet, 7.2 will be fine?

Neildo_64 · Post by **Neildo_64** » Thu Mar 09, 2006 6:32 pm

Yes, 7.2V should work. It says 9V but some of the users here at the forum have tried it (including me) and it works at 7.2V.