http://ameblo.jp/maseki-owarai/entry-10638023846.html
D+に2.8V(33kΩ,47kΩ),D-に2.0V(22kΩ,33kΩ)を分圧することでiPhoneに対応しているようだ。
http://junkhack.wordpress.com/2011/02/10/%E5%8D%983%E9%9B%BB%E6%B1%A02%E6%9C%AC%E3%81%A7iphone%E3%82%92%E5%85%85%E9%9B%BB-%E3%81%9D%E3%81%AE5/
http://www.ladyada.net/make/mintyboost/icharge.html
The four resistors create a voltage at each of the data lines thats not 3.3V but rather 2.8 and 2.0 (or so) volts. The problem is that when you do this, the iPhone starts to draw as much as 1Amp
