I'm planning to build a USB OTG cable for a Nexus tablet mounted in the car. It's a Y cable, which takes 12V input from the car, sends 5V out to the tablet, and 5V out to an OBDLink SX device. The USB data pins will connect the tablet to the OBDLink, and the 'sense' pin on the micro USB side is shorted to ground with a 100k resistor to trigger the Nexus into host mode. I know these cables are cheap on Amazon, but I want to customize the lengths to make it look clean.

This tablet likes a 5.2V input and I can't find any fixed regulators of that spec. So my question is how to use an adjustable one, for example LD1084V.
Input voltage can vary between 11-15V. Output voltage needs to be fixed at 5.2V.
The datasheet says Vo = Vref * (1 + R2/R1) and Vref = 1.25 (varying between 1.237 - 1.263)

So if I make R1 = 7.5K and R2 = 23.7K then the output voltage should stay within 5.15 - 5.25V. I've just never used an adjustable regulator, so do I have this all right?

 

One more question: How can I solder a through hole USB receptacle to a perf board? All the data sheets I can find show uneven hole spacing that won't fit a regular board. It's 2mm between the center pins and 2.5mm between the others Example: http://cnctech.us/pdfs/1002-001-01000.pdf

 

Your best bet will be to use an already available converter. Unfortunately a car's electrical system never really stays in the 11 - 15 volt range. Check out load dumps and transient voltage to see what I mean. Other than that there are lots of solder together USB cable ends online to make your own cables.

 

One more question: How can I solder a through hole USB receptacle to a perf board? All the data sheets I can find show uneven hole spacing that won't fit a regular board. It's 2mm between the center pins and 2.5mm between the others Example: http://cnctech.us/pdfs/1002-001-01000.pdf

Use a piece of copper clad PCB and make s sandwich of it and the perfboard. Scratch in the receptacle pin locations and drill through both boards. Remove the sacrificial copper clad, and insert the receptacle. A bit of solder will fill the drilled holes and keep everything in place.