Sunday, July 31, 2011

What am I up to?

Just a sneak peek at what I’m up to lately. Can’t reveal too much information just yet. Will do so in a later update.


Monday, July 18, 2011

National’s New LMZ simple switcher module series.

Currently developing a power supply solution for the Xilinx Spartan 6 LX150 FPGA, and I stumbled across this cool modules from National.

They’re available in 1A-10A capabilities, if 10A is not enough, there are modules out there that can current share, for up to a max of 60A output.

The modules themselves come with an intergrated FET and inductor, meaning you don’t have to make a choice, don’t have to worry about best layout on your board, and it will magically just work.

Very low external parts count, you just need 2 resistors to set the voltage and then a bunch of capacitors and away you go.

Prototype friendly package, the module is housed in what looks like a D2Pak layout (except with a couple more pins), enabling good thermal performance and ease of solderability (compared to say QFN).

Low EFI/EMI, the inductor and FET are shielded inside the module, meaning you wouldn’t need to worry about component placement on the PCB.

There are a whole other bunch of benefits, the only cons being a slightly higher initial cost and no way to tweak say the FET or inductor to a ‘better’ part because they are built in.

Web-bench enabled, this web based app will spit out the schematic, BOM and let you simulate electrical and thermal performance for your spedified inputs and requirements, makes gauging what kinda performance you’ll get in your final design easy.

The list goes on and on and on. Check them out on.

Anyways here’s my PSU design at the moment.


Tuesday, July 12, 2011

Speedtouch ST536v6 Repair

Came home one day to find my modem’s lights were all out. Abit of probing with a multimeter found the adapter to be dead. Thinking that it was just the adapter, I dug out a replacement and put it on. Things went downhill further when something on the board released it’s magic smoke and the modem wouldn’t sync properly (everything was there but the ADSL link light wouldn’t come on steady).

Visual inspection near the vicinity of the smell, I found the receiving buffer, an STmicro TS613I part visibly burnt. Oh well… I don’t really like throwing out stuff, even though I’ve got a couple more spare modems on hand I think I’ll fix this (it’s been working very well for the past 4-5yrs actually).
A search online on my favorite parts suppliers (RS/Farnell etc.) didn’t net me any results, they didn’t carry the specific part. Then I thought I’d try TI, they ship samples out fast and Burr Brown has some insane Opamps I’d like to try.

A search on TI’s keyword based system found me this.

OPA2613, it’s even listed as a TS613 replacement, aha! I thought it’d be a drop in replacement, but it looks like it’d take a slightly lower max voltage. The rest of the specs (noise, slew rate etc.) were looking better then the original part. I ordered a couple of samples and they shipped it out within 2hrs through FedEx International Priority with a tracking number.

3 days later I had the part in hand, I love the super fast shipping, thumbs up to them, and I proceeded to remove the old part, replace it, and then make modifications necessary to make it work reliably.


Here I’ve taken out the fried TS613, I think the part failed after prolonged use because the input voltage drifted over it’s max rating (the voltage source is fed from a LM7812 with a couple of external resistors to set it’s output voltage close to 14v, however one had drifted in value due to the heat or maybe it drifted because of the fried TS613? Wouldn't know for sure.) and I measured 14.5 (not a safe working voltage for sure, datasheet for the OPA posted a max rated working voltage of 12.6), I don’t know why they went with such a small margin for error, and it really seems like they were pushing the envelope (even the TS613 recommends it’s operating supply to be @ +/-6V, making it a total of 12V). I’m guessing they needed the extra voltage to make sure the output wasn’t clipped or something.

Here’s the fried TS613


Prepped the board with some flux and wicked off the excess solder. I had to remove a capacitor off the board for some clearance around the part.


Here’s everything in, OPA2613 and capacitor.


I modified the supply back to 12V (from 14) by removing the 2 external resistors and then tying shorting the GND of the 7812 to the board’s GND.


It now works, I’ve yet to experience any sorta dropout in connection yet. Will update if it does die or something again.

Monday, July 11, 2011

Turn Aquarium Pump into Vacuum (Cheapie pickup tool)


I needed some way to suck small SMD parts up without having to buy a $$$ vacuum station. Already had a cheapie $2.50 pickup tool (with a rubber bladder thingy), but that wasn’t working all that well especially if the component doesn’t have a completely flat surface. The pen will eventually loose vacuum and cause the part to drop, and you don’t want it to drop when you’re not prepared, it’s almost impossible to find it later.

A good friend passed me an aquarium pump to see if it’ll convert over (thing costs less then $5 new). Here it is intact.


Taking it apart reveals a rubber bellow and some kinda diaphram valve system. To make it suck instead of blow you’d just have to rotate the valve around so the sucking side now goes to the port.


Here’s the diaphragm/reed valve system.


I ended up having to cut away a couple of positioning pins, because the new location doesn’t have holes for them to go into, and then using a drop of glue to hold everything square while I tightened the center screw.

It works, I can now suck up parts and not worry about them dropping randomly.