Cell Phone Car Charger

The goal of this project is to demonstrate the design, simulation, and construction of an in-car cellphone charger. The entire process will be recorded on video for educational purposes.
 

 

 

Specifications
Input: Car Battery 12V nominal (11.4V-12.9V)
Output: 5V, ~0.5A cell phone charger

Design Parameters
Vin: 12V +/- 2V
Vout: 5V
Iout: up to 1A; +/- 50mA ripple
f_sw: 500kHz

Component Selection
IC: TPS5410: 1-A Wide Input Range Step-Down Swift Converter from TI
I have listed some possible components to use in the charger.

• A simple TI controller with integrated switch. The only problem is it has a 1 Amp current limit and we want 0.7 Amp limit. It also has a max switching frequency of 52 kHz.
• Another TI controller with integrated switch. This one allows use to set a peak current limit I think. Its max switching frequency is 100 kHz.
• Another TI controller with integrated switches. This chip has integrated synchronous switches and allows switching up to 1 MHz. I think something like this one will be the best. It comes in a tiny QFN package so we may want to find something a little bit bigger.
• After much searching, this part seems to be the best one: TI TPS62112 I've order 4 free samples from TI. The main problem is that the QFN packaging might be smaller that we want. I think we might just have to learn to live with it though. I couldn't find a suitable replacement that was any larger.

I found a company that has QFN to DIP adapters. You can send the QFN IC to them and they will solder the part on to their adapter and mail it back. It costs about $9 for the adapter and $9 for them to do the soldering, per IC. The website is here.
Another option might be a QFN socket. This is one possible company.