Resistor Values for a USB Charger.

[QuestionablyHuman]

I want to build a USB charger for my iPhone. I know that for slow charging speeds on the data pins you need to have 2.0v each, which can be achieved by connecting a 75k resistor to 5v, connecting the data pin to that, and then connecting a 50k resistor from the pin to ground. I want to do fast charging, so one data pin on the USB port needs to be 2.0v and the other needs to be 2.7v. Does anyone know of the correct resistor configuration to achieve that from 5v? It's going to be a dedicated iPhone-only port, so cross-compatibility is not an issue. Any help would be very much appreciated!

 

[davenn]

I want to build a USB charger for my iPhone. I know that for slow charging speeds on the data pins you need to have 2.0v each, which can be achieved by connecting a 75k resistor to 5v, connecting the data pin to that, and then connecting a 50k resistor from the pin to ground. I want to do fast charging, so one data pin on the USB port needs to be 2.0v and the other needs to be 2.7v. Does anyone know of the correct resistor configuration to achieve that from 5v? It's going to be a dedicated iPhone-only port, so cross-compatibility is not an issue. Any help would be very much appreciated!

welcome to EP

google is your friend

have a look through these links
http://www.bing.com/search?q=I-phon...-17&sk=&cvid=3933359F2EB04A7E87731C0124532CF4

 

[QuestionablyHuman]

I've looked through everything and the only thing people seem to do is 2.0v and 2.0v. I really have no idea how to calculate the resistance or resistors needed.