SMD LED Camera Flash

Howdy! I'm Dominic, and although I'm a digital and 3d artist, I'm not exactly a novice at EE, but I'm not an expert. I'm working on a project right now, and I'm kind of venturing outside of my comfort zone. Problem is, the circuits are getting more complex and the components are getting smaller, so I'm looking for some help with designing them, pretty please of course.

So the first circuit up is an SMD camera flash, which I'm sure it's going to be so incredibly simple, but I just haven't found the right circuit to model it after yet. I'm debating what LED's I'm going to ultimately choose, but I have a couple in mind

# https://www.superbrightleds.com/moreinfo/surf...samsung-natural-white-5630-smd-led/1385/3189/
# https://www.superbrightleds.com/moreinfo/comp...ds/samsung-cool-white-5630-smd-led/1383/3187/

There's two ways to go about this. I have one other circuit modifying 2.2V from one source and if possible I'd like to use this power. The only catch is that I can't cause the 2.2V to drop, so it has to stay 2.2V all the time. Or I can just use a coin cell, but then that's less cool.

The 2.2V source is wired to a small board with a resistor and a pushbutton. The button is pushed causing a drop in power and signaling the device to take a picture. Basic, but now you understand why the power can't drop; it'll defeat the purpose.

So if there's a way to use a capacitor to pull and store that power on a new circuit and then use it to power the LED as a flash (and possibly hold the flash for a couple seconds), that's the goal.

So what would I have to do?

Thank you guys so much!

Hi, take a look at this:
http://www.analog.com/en/power-management/display-and-lighting/adp1655/products/product.html

For flash you probably want the cool white as it resembles daylight the best, if you also use it as a light, the 4000K is a nice neutral color.

So basically it's the entire control circuitry rolled in an IC? Just add an inductor, caps, and two less? Nice. Only thing is I'm barely going to be scraping 50mA at 3.3v, so do you think this is still a good option? I have to use as little energy as possible

I've been playing with the 555 last couple days, and I found a monostable design that would work fantastic. Only thing is I want the led to flash twice (like most camera flashes do to aid in focus before shooting), and I have no idea how to do that with the 555.

What do you think?

Yes, it's all the engineering already done for you on a chip. Also very small on the pcb. Current and flash times can be programmed via the i2c pin. Just hook it up to the controller you're using. The flash currents are isolated so it's not going to create a drop on your input voltage. But that's all in the datasheet. I don't think a 555 is going to compete with any of that, unless you're not using a microprocessor/controller and I understood wrong.

No microprocessor. It has to basically be a more or less analog circuit.

At the level you are working at, that chip will be no help, it is a very small solder bump part.
They do have an evaluation board however, but if you are not using a micro, you will need to take another approach. The dual flash system might work with two 555 parts.
Cheers,
Richard

This is what I came up with. I'm just going to use a single 555 in monostable, but thiswill be just fine. I've discovered a two flash system may not be the best approach due to variables I can't control in the system. Thanks!

And I'm upconverting the 2.2v to 5v with the LT3427 IC. Do you think that's a good chip to use?

I take it that you don't want to be doing a PCB just yet. The LT3427 is in a DFN package, very difficult to work with if you haven't done much electronics construction. If the chip is available on a demo board OK, otherwise you will need an alternative part.
You may have to go to the various integrated circuit manufactures web sites and look for demo boards for their products, and try and find something that would do what you want.

Well I've actually put some PCB's together before, so it's not my first rodeo. I just don't usually work with IC's.

The datasheet actually shows you the proper placement and construction for this specific chip which is totally awesome.

Hi Dominic, you won't be able to work with this chip unless you have access to a reflow oven,or can get the soldering done by a local PCB manufacturer, the pad under the chip is not accessible. In the long run, you may want to do this, but for prototyping it could be a difficult exercise, all the best,
cheers,
Richard

Oh I"m definitely aware of that issue. I have access to what I need to get it done :)

The other chip I was looking at was the NCP1402. It has a much lower amperage, however, so by my estimates I'd be pulling about 50mA max. The LTC3427 though would leave me with a considerably higher current. But I could very well be wrong and the NCP1402 could be fine for what I'm doing. Ideas? Thoughts?

Decide which are the most critical parameters, find that information in the respective data sheets, and see which part meets your needs best. A TSOP or SOT part
is easier to work with, you should be able to hand solder the parts onto a PCB yourself, which makes prototyping much easier.