17mm/22mm MTN-MAXlp - Low-Profile 1A-4A Programmable Buck Driver + 22mm MTN-MAX

Just checking!

Can you measure what pulldown resistor value you have? 19.1K or 36K? Sounds like I might have given you a 36K which is my preferred resistor for that driver, but with guppydrv you might need the 19.1K.

I did measure before it got stuck on. It’s a 36k

If you’ve got a 19.1K, I’d put that on there and give it a try.

Or if not maybe get away with stacking another 36k?

That would work as well, if you have one. I am going to send him a few resistors.

Thanks a bunch.

Finally had a chance to play with this today so I changed the pull-down resistor to 19.1k. I am still unable to enter configuration mode. When the 36k was on before I could have sworn it had 4 modes. ML-L-M-H. Now it’s 3 modes. It seems as if the timing is quicker than before. It still stays in 1 mode if you go to fast.

The timing, even with the correct resistor, is a bit tricky. You can't just tap the switch as fast as possible like on most drivers. There is sort of a rhythm to it. It usually takes me a few tries before I get it.

Yeah I keep trying but… I don’t get it, I know it’s there but I can’t catch it. :–5

Did you ever get it going?

Hopefully if I get some time later this week I will post up some new variants that I've been working on for a while, that are finally ready to go:

  • Updated 17mm MTN-MAXlp HP
    • Increased efficiency
    • In-system-programmable
  • Updated 22mm MTN-MAX
    • Increased efficiency and stability; fixed a few small bugs
  • New 26mm & 27.5mm MTN-MAX

No I've done all I know to do but can't get into programming. The timing just isn't quick enough or something. I have been meaning to ask you if I should stack a 36k on there and try it.

I have been burning thru some primarys with it though. It's a 3.5 amp so in high it steps down in like 3 sec (with fresh batteries) but it's still more than 500lm and lasts a long time so I'm happy with that. That's not the way I intended to run it all the time but I just wanted to know how it would handle them. It gets really warm for the first 20 min or so but after that it's fine.

I would be worried a bit about pushing those primaries that hard. Rule of thumb is 1.5A maximum continuous, so you're pushing them a bit harder than that probably. Be careful!

When you switch modes, do you feel like you have to tap the switch really fast, or do you have to wait a moment before it will switch?

I have to wait a moment to get it to switch.

Yeah I was worried about it too and have been paying close attention to the batteries. They're not really getting hot. It's the driver heating. I was thinking that when it steps down (almost immediately) it wouldn't be pulling the max from the batteries?

If you have to wait, then stack another resistor on top of the existing and try it.

I now have 2 19k resistors stacked. 9550 ohm? The mode changes are quicker and I am able to enter configuration mode and select the mode group. Seems to work like it should now. Thanks Richard. I do believe I’ll be getting a couple more of these soon.

Glad you got it working!

I usually haven't had that much of a hard time with guppydrv ones, but it does take a bit of timing to get it.

OK, finally got time to get the new 4L 17mm and 2L 22mm uploaded and shared. Should I keep everything in this thread and just update the OP, or should I start something newer and tidier?

17mm 4L v1.1 w/ ISP Programming (of course, more details to come)

22mm 2L v1.12

You will notice that besides the ISP on the 4L, there is a new part on the board. I also need to update some of my component recommendations, especially those regarding inductors.

In the end these drivers are still pulse width modulate for lower modes right? As in the LED sees on/off pulses right?