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

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shrick
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shrick wrote:
I have the c682 coilcraft inductor. At the bottom it has 2 contact plates on each side and a black pad in the centre. I presume the black pad is the termal pad? Richard mentions one has to reflow the thermal pad? On the pcb underneath the black/thermal pad theres silkscreen, no place for reflowing? What is meant by reflowing the thermal pad of the inductor to the pcb?

Mmm, I realize now the thermal pad is that of the buck IC, not the inductor. Apologies! Please ignore my comment.

Rufusbduck
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Some SMD parts have solder pads not exposed or visible with the part in place and these can’t be soldered using an iron but need a hot air reflow system, a reflow oven, or some way to heat the entire thing up to the solder melting temp. For some things you can use a hot plate and carefully monitor it but two sided pcb’s can get tricky if it has such parts on both sides. Otherwise you could reflow the difficult part first and then solder the remaining parts with an iron.

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Scott

shrick
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I’ve been struggling for some time now (2-3 weeks) to get my MTN-MAXlp HP build stable. I have already communicated directly with Richard around my issue, but I still don’t have a solution. It seems like Richard has had great success with this driver up to now. So, I’m taking a chance here, maybe somebody had a related issue.

My first driver build was fine. The only problem I had was that the mode switching was too slow, so I changed PLDN 19.1k to 4.7k. After this, the driver was great. I’ve configured it for 5.5 amps output running XM-L2 U4 – 4 modes, starting on Turbo. All was great, including the 478kcd!

I then built my 2nd driver, EXACTLY the way I’ve built the 1st one (including the same program). The issue now arose -> I could not switch/change modes. I only had max output, no matter how fast or slow I tried to change modes, no go. Just max output.

I then decided to build a 3rd driver. Once again, exactly the same build, the same program, the same issue! I then took this driver, reprogrammed it a few times setting a lower turbo mode, just to see if the driver will turn on at a lower amperage, which it did. The problem seems to be mode switching only, its start off at the correct mode. I’ve probably reflowed the MMU around 15 times during the diagnostic process, every time the same symptoms. I’ve replaced that MMU at the end with a fresh / new one (I’m so paranoid at the moment) – still the same issue.

I’ve fiddled around with the PLDN resistor going up & down with the resistance – did not help.

Has anybody experienced what I’m experiencing now? I’d very much appreciated any help.

pyro1son
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Could there be a short in the traces of the board that means that it just goes into DD?

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shrick
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pyro1son wrote:
Could there be a short in the traces of the board that means that it just goes into DD?

I do get lower amperage readings after reprogramming turbo mode with lower values…

RMM
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Also, there is no way that there are that many bad boards, and I have been building them with boards from the same batch.  I admit that I am a bit stumped as well. Frown

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RotorHead64
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I just assembled one of these today (3.5a w/guppydrv) and it works great. The timing is definitely different but not in a bad way. My problem is I can’t get it into configuration mode. If I tap to fast it never changes modes, to slow and it just cycles thru. M-L-Med-H. For me it’s fine the way it is but I can’t help but wonder what’s wrong?

wight
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I’m just checking here… but did you assembled one of the drivers in this thread or the MTN17dd you mentioned recently?

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

RotorHead64
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wight wrote:
I’m just checking here… but did you assembled one of the drivers in this thread or the MTN17dd you mentioned recently?

Yes this one. 17mm MTN-MAXlp. The other post was for MTN17dd…

wight
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Just checking!

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

RMM
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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.

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RotorHead64
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I did measure before it got stuck on. It’s a 36k

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

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

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

RMM
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wight wrote:
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.

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RotorHead64
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Thanks a bunch.

RotorHead64
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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.

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RotorHead64 wrote:
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.  

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RotorHead64
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Yeah I keep trying but… I don’t get it, I know it’s there but I can’t catch it. Facepalm

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RotorHead64 wrote:
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? 

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RMM
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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

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RotorHead64
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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.

RMM
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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? 

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RotorHead64
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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?

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

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RotorHead64
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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.

RMM
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Glad you got it working!  smilesmilesmile

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.  

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RMM
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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.

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

RMM
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Flintrock wrote:

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

That is correct.  You can't see it or hear it, but it is PWM.

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