2.5V @ 1A from 12V - Page 1
Forum section: electronics / projects

author: brainwash
author_rank: Frequent Contributor
timestamp: August 02, 2013, 12:32:34 am
content: I have to make a few (2-5) of these boards and wondering what are the most simple and reliable options are available.The requirements are 2.5V, 1A continuous, 1.5A peak, ripple <150mV, supply 11.8-13V. Efficiency does not really matter.I guess LM317 or similar are out of the question since they will have to dissipate almost 10W.The previous design was based on a AP1501 5V 3A DC buckregulator followed by AIC1084 5A 2.5V LDO, but those (factory) boards have a pretty high failure rate. Ok, it's actually an assembly problem but it made me wonder what are the recommended options for achieving this output.

author: krivx
author_rank: Frequent Contributor
timestamp: August 02, 2013, 12:37:23 am
content: An lm317 with an external pass transistor will do it if you just need something quick and simple. The TI datasheet has an examplehttp://www.ti.com/lit/ds/symlink/lm117.pdf

author: ampdoctor
author_rank: Frequent Contributor
timestamp: August 02, 2013, 01:51:59 am
content: So if I understand the question properly, you need 2.5v from approx 12v unregulated dc supply going into a regulator? Unless there's a lot of missing pertinent information, I would think that your entire supply needs to be seriously re-evaluated. If you're pretty much stuck with it as is, and depending on the application, you might consider as another alternative using a 317 or whatever, and regulate the dc down to 9v or a little less. At this point you can start dumping voltage across a couple of series RC filters. Yes I know it would use substantially more real estate and be more expensive, however for a quick and dirty solution it should be pretty damn reliable, so just thought I'd toss that option on the pile as well.

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: August 02, 2013, 01:55:47 am
content: Check out this short article on a 24-12 – 5 volt @ 3 amp module I got from eBay. Something like this is probably your best bet.A Look at Switching DC-DC Converters

author: brainwash
author_rank: Frequent Contributor
timestamp: August 02, 2013, 02:30:22 am
content: Ok, I missed on clarifying a few points:- it has to work from 12V, that the external PSU. How it gets from 12V to 2.5V is not really important, it can be in two stages like the current design- I have a few LM2596 modules, supposedly rated at 2A. They get really hot, I have not tried testing them for 24h.- the 12V input is not a car, it's just something like a laptop power supply but there are a few intermittent loads on that railI am really open to all suggestions and reading each post, so thank you for your contributions.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 02, 2013, 02:54:00 am
content: If efficiency really doesn't matter, maybe a linear regulator with a power resistor handling the bulk of the dissipation?

author: amyk
author_rank: Super Contributor
timestamp: August 02, 2013, 02:56:02 am
content: 2.5V and 1A is around the supply voltage and current of DDR RAM, so you could take a look at e.g. MAX8551.