0.25 -0.5 us delay repeated with 60 Hz frequency


Hm, original spec that I got from Wurth web site does not have it.

Super! I will try to program 328 using UNO and will report.

Peak Forward Current : 1000mA

Probably the pulse condition is written below it.

I'm driving them with industrial ICs LED drivers. The only problem is that the max current that I can get with On Semi ICs is 350 mA. They can run in parallel but having 3 for 1A current is not a very elegant solution.

Would it help if you posted
1: a link to the spec of the ACTUAL LEDs you are using?
2: a link to the spec of the ACTUAL drivers you propose to use?

The link to LED spec is in # 20.
Here is the link to the ICs. https://www.onsemi.com/pdf/datasheet/nsi50150ad-d.pdf

So put 3 leds in series, increase supply voltage and set current to 350mA. Same light output (more or less) as one led @ 1A.

Or use a different led driver.

Btw, you have a timing problem if you want to make pulses of the short duration you're planning for. Datasheet of the driver, page 7:

The switching time is in the order of 100 nanoseconds

Oops. So 62.5ns is out of the question, and anything below 10x the switching period I would consider sketchy to begin with. So for all intents and purposes I wouldn't consider these led drivers for pulses shorter than 1us since they are likely to be unpredictable in terms of regulation (especially if you expect a 100ns pulse to be exactly half as 'bright' as a 200ns pulse etc.). Not to mention that the startup behavior isn't really specified, so you have no way of knowing how these drivers handle such a situation.

I think you're better off devising a linear regulation scheme for this from discrete components. It'll be somewhat tricky though given your <100ns requirement. Even N-channel MOSFETs can become somewhat problematic in use if you need consistent switching speeds in that region (you need to think for a few minutes about an adequate gate driver).

This is why I intend to use 250-500 ns pulses with the LED so my optical pulse < 1000 nc. I don't need shorter pulses for this one. In my LED device I use hundreds of LEDs and my LED boards contain both LEDs and a driver. When I designed it I did not have intentions to overdrive LEDs so I don't actually have room for 3 LED drivers on the board. In theory I can build a simple current driver based on LM317 but the size of the circuit will be bigger than 2 NCI drivers and I doubt it will be regulating as well as NCI driver. Ideally I need 1 A ICs but I could not find one. Another issue here is that I will need 10A power supply (for 10 LED arrays) which is not desirable in this application so I would have to add charging cap so I can use 1A power supply.

67 and 120 nc pulses are for LDs which need a different driver circuit based on avalanche transistor. I have MOSFETs with very low gate capacitance so it should not be a problem. It is a future project anyway.

Hold on, you expect 250-500ns control pulses to generate ~ 1000ns light pulses? Have you established this latency through measurements?
I'm not sure if you got the gist of my comment, but I foresee problems with 250-500ns pulses, and certainly with pulses shorter than 100ns since they are either close to, or even below, the switching speed of the led driver, which apparently is <100ns / 10 MHz. There may be problems with e.g. overshoot and ringing that result in the light output scaling extremely non-linearly with the pulse period.
See also further on page 7:

The LEDs and the CCR switch extremely fast, less than 100 nanoseconds.
It's not entirely clear if this implies that the control frequency is actually 10MHz, or that the switching propagation delay is 100ns, which would imply a far lower control frequency (let's say 1MHz and lower). In my experience, integrated led current drivers tend to work at frequencies of 100kHz - 1MHz. Trying to use pulses under 1us seems rather problematic to me if any kind of consistency is a requirement.

Yeah, but don't :wink: Been there, done that. Besides, I doubt it'll be fast enough for your application, regardless of space requirements etc.

That would help, indeed. Frankly, I'd investigate that route a bit more instead of the led drivers you currently use. I don't think they're quite up to the job you have in mind for them. Not in the future project, but also not in the current 'slow' project that apparently requires 250-500ns pulses. In your place I'd brew a nice cup of tea and spend an afternoon playing around with Spice.

I did not have much luck using UNO as a programmer for Atmega 328. I had similar problem with Chinese made Attiny 85 which had disabled clock. Will try Nano on Saturday and will measure the pulse. I'm not sure if the spice model for the driver is available. I could not find one.

I don't know about the programming problems of Atmega's & Attiny's. All 328P's, 328PB's and Attiny85's I've had from China so far programmed fine over SPI.

I wouldn't even bother looking for it. I think you're better off with a DIY-driver made from discrete components.

Remember, the ONLY heat sink the die has is the wire leads. They have to dissipate 200 milliwats to your circuit board.

My average power is 50mW so it should be OK otherwise I would use SMD s and put them on a heat sink or Al PCB with fan.

Ok, but PEAK power is what is in the LED die.

The code works and so far the shortest pulse I measured on Pin 8 is 250nc!
Thank you very much!