I would like to make an universal USB charger. I have a 5V, 2A max generator and I can not find any electronic assembly to create a Dedicated Charging Port able to charge Samsung, Apple and other devices.
I read the entire USB Battery Charging Specification and in my case, I need to meet Dedicated Charging Port tests.
a) Have a 200 ohms resistance between D+ and D-
b) Have a leakage current from D+/D- ≤ 300 Kohms tied to a voltage between 0 & 3.6V
c) Have a capacitance from D+/D- of 1nF
d) Have VBUS discharge functionality
But It appears that most things do not even met these specification as shown in this other topic: USB downstream port examples.
So which one to choose?