FS: The MicroDrive SLR Boost Driver

[Hiemal]

The MicroDrive SLR is a small boost driver designed for small spaces, and low current ripples.

Front:

Back:

Pinout:

This driver only gives out about 40 mA of ripple when pushing over 1.8 amps of current, boosting from 4 volts to 5 volts.

It features:

overheating protection, causing the output to strobe.

Disconnection protection, preventing the driver from self destructing under disconnection conditions

Extremely low ripple currents, due to the large amount of capacitance on the output.

Super soft start signature of all of my drivers. Zero spikes from startup on this driver.

Continuous ground, none of that isolation or weird wiring nonsense.

Super Small Size, measures only 8.64 mm by 8.82 mm.

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These boards are adjustable from 300 mA, to above 2 amps depending on input/output voltage ratios. For a blue diode, the driver should be capable of about 2 amps output.

This is a rough estimate, but when you're pushing above 1.5 amps it generally requires a heatsink. If there is no heatsink connected the output will begin to strobe signalling it needs to cool before use again.

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Note:
When adjusting the driver use a fine touch and small screwdriver; if the output drops a large amount turn the potentiometer back a little and disconnect and reconnect the battery. This is a feature of the driver that prevents overvoltage conditions. This goes for when you're adjusting from low to high and high to low. You have NOT killed your driver.
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Still not convinced?

Here's a video of the driver showcasing the capabilities.

Any bizarre fluctuations shown on the oscilloscope are due to me hooking up connections/changing things on the board. There is NO danger to any laser diode you connect.


I currently have 0 of these in stock. Once again, they are adjustable from 300 mA to 2 amps. I'm asking $18 per board, plus $2 shipping anywhere in the continental US.

I will be making more of these, in bulk when I get the chance, these are just pre boards to gauge interest.

Thank you for looking!

 

[rhd]

EDIT: Cool! Watched the video with sound. Looks good You should post some screenshots of the scoping.

 

[crazyspaz]

Vid doesn't work (you have to use just the tags, the string of characters after the = in the youtube link). I may snag one from you

 

[rhd]

Looking at your design, it occurs to me that you should see if you can find the AX5525 IC. I've never been able to find them actually for sale, but if you can find them, they're the same package and they look pin compatible with your design, and would allow you to kick the current up even higher. They have a switch current of 5.5A, so that would be enough to handle 2.3A output throughout a wide range of the typical lithium ion discharge curve.

You might even want to consider the AX5523, which only has 4A switch current, but might still be a step up (maybe not, I'm not sure what you're using now. The AX5523 is a little easier to find.

 

[Hiemal]

Looking at your design, it occurs to me that you should see if you can find the AX5525 IC. I've never been able to find them actually for sale, but if you can find them, they're the same package and they look pin compatible with your design, and would allow you to kick the current up even higher. They have a switch current of 5.5A, so that would be enough to handle 2.3A output throughout a wide range of the typical lithium ion discharge curve.

You might even want to consider the AX5523, which only has 4A switch current, but might still be a step up (maybe not, I'm not sure what you're using now. The AX5523 is a little easier to find.

I tried looking at various common suppliers and yeah, can't find the AX5525.

Vid doesn't work (you have to use just the tags, the string of characters after the = in the youtube link). I may snag one from you

Thanks, I fixed the video!

 

[Hiemal]

So some scope pictures...


Soft Start:

OverTemp Protection Strobing:

No connection, to show the scope's noise:

And the ripple (you have to mentally subtract the noise, but it's about 25-30 mA or so)

Keep in mind this was with an output of 1.8 amps. Meaning a ripple percentage of only 1.38%, if i did the math correctly.

 

[The Lightning Stalker]

I like how you draw little arrows on there.
Can they boost to 7V, and if so, how much
current?

 

[Hiemal]

I like how you draw little arrows on there.
Can they boost to 7V, and if so, how much
current?

I haven't done a formal measurement but yes, they can boost to 7 volts. At what current, should be about 1.2 amps or so, I'll do some testing tomorrow to figure out a specific number for you.

 

[rhd]

For anyone who doesn't know, reflowing such tiny boards takes a lot more time than reflowing nice big 12x9 boards like a flex drive. The fact that these are being sold for $17 is impressive!

 

[The Lightning Stalker]

Yea, it looks like he is using 0603 in some
places. Those can be a pain, though not
quite as bad as mixed 0603 and thru-hole with
tinned traces.

 

[Hiemal]

They're not actually that difficult to make, though I appreciate the words of praise. :yh:

Yes, they are 0603 caps mixed with some 0805's. Oh, and one teensy 0402 resistor. It's hard to see but it's above the potentiometer on the back. Always have a few issues trying to get that sucker aligned.

It's a welcome change from QFN and pinless packages though, I do have to say.

 

[Hiemal]

Went ahead and did some measurements like I promised Lightning, and it looks like it should be capable of about 1.1-1.2 amps of current to 7 volts. I couldn't get the v-drop exactly on 7 volts, (I was getting 1.4 amps on 6.5 volts and 1 amp on 7.7 volts) unfortunately, so it's an estimate.

 

[Jstr]

^very impressive. That is with an input voltage of 4.2, I assume? How is the ripple when boosting that much? Is it suitable for driving a 405? If so, I would definitely be interested in a couple. (would only need ~700 mA though)

 

[Hiemal]

^very impressive. That is with an input voltage of 4.2, I assume? How is the ripple when boosting that much? Is it suitable for driving a 405? If so, I would definitely be interested in a couple. (would only need ~700 mA though)

I actually went back and remeasured the battery, and through my testing it had dropped to 3.8 volts.

With a fresher battery at 4.1 volts, it can deliver about 1.35 amps at 7.7 volts boosting, with a ripple of about 40 mA.

it'll definitely be able to drive a 405 nm with no problems, and the ripple'll be lower, about 20-30 mA.

 

[The Lightning Stalker]

What is the ripple like @300mA - 500mA?
The PLP520-B1 likes to run 7V @ 500mA, but
a 40mA ripple might kill it.

 

[Hiemal]

So I actually had to redo the number of tests I had done, primarily because of bizarre parasitics and whatnot. The little switching supply I had on my test load was actually adding little spikes to the ripple and to fix it a 9 volt battery directly powering everything vs. a 18650 boosted.

And also, funnily, my multimeters actually add a deal of noise too, so I had to do some fancy handiwork to get around all of these sources of noise. I tried seeing if I could use my scope's internal filters to get around it but I got worried it would just remove the actual ripple I wanted to measure too. So, no filter, and some basic math.

So, new measurements.

Boosting from 3.8 volts to 5.01 volts at approx 1.98 amps, I get a ripple of what SHOWS to be 30 mA.

The noise however adds 10 mA to this from all of the sources, so in actuality the ripple is 20 mA.

Boosting from 3.8 volts to 7 volts, at 500 mA, I get a ripple of what APPEARS to be 22 mA. Again, noise is 10 mA, so about 12 mA of ripple. So, very low noise and great for 405 nms and whatever other high v-drop diodes you wanna connect.

Also, oddly, when I add a 0.1 uF cap across the inputs of my test load it removes some of the ripple/noise but when I add it DIRECTLY to the board, there's no change. I think the wires are actually adding some parasitics that increase the noise/ripple and the cap removes it.

The board also does NOT like boosting above 7.7 volts at high currents. A ton of ripple and oscillations start flying around everywhere. Everything below that, peachy.

Would I feel comfortable saying hook it up to sensitive diodes? Sure. Just be careful with your current settings and maybe shoot for like, 5-10 mA below what you were going to use to account for ripple.