eanema
Member level 2
There is a huge number of PC projects that steal power from the USB port with out paying attention to the current limits set out by the USB standard. The problem is that my phone, as well as many other professional USB devices *do* consider the maximum current draw.
I am wondering if there is an IC that is designed to sit on a 'USB charger' (as in a USB port sitting on an AC wall adapter) that will tell the device that it is OK to take as much power as the device requests? Through an enumeration process may be?
I have read that on certain devices like the iPhone g3 you can use voltage dividers to apply specific voltage on the data lines to signal the device that it is OK to take power. Apparently the Motorola phones have a 5th pin in the USB port that can be controlled to tell it to take power.
The problem with these configurations is that they are not universal. If all these devices will charge off the USB port when properly enumerated, then to charge them you simply must enumerate them.
Is there an IC that will do this with out using a full blown USB host IC?
I am wondering if there is an IC that is designed to sit on a 'USB charger' (as in a USB port sitting on an AC wall adapter) that will tell the device that it is OK to take as much power as the device requests? Through an enumeration process may be?
I have read that on certain devices like the iPhone g3 you can use voltage dividers to apply specific voltage on the data lines to signal the device that it is OK to take power. Apparently the Motorola phones have a 5th pin in the USB port that can be controlled to tell it to take power.
The problem with these configurations is that they are not universal. If all these devices will charge off the USB port when properly enumerated, then to charge them you simply must enumerate them.
Is there an IC that will do this with out using a full blown USB host IC?