I would like to design a 2-port bus-powered hub into an iPhone dock product, using the TI 6-MHz 2-port ref. schematic as a starting point. I am not planning to use an EEPROM.
One downstream port will be internally wired to the USB pins on the iPhone 30-pin dock connector, the other port will be available for another user device (when the upstream port is connected to a host). The goal is to have the iPhone charge itself when the hub is bus-powered by a host, and also charge itself when an iPhone wall charger is plugged into the upstream port (no host).
The Apple charger provides +5-VDC and has resistive dividers that set DP to +2.0-VDC, and DM to +2.8-VDC. These voltages queue the iPhone about its charging rate. The TUSB2036 would see these fixed DC voltages on DP and DM when the wall charger is plugged into the upstream port. Will the TUSB2036 and reference circuit still provide +5-VDC to the downstream ports without a host and with these bias voltages on DP and DM? Is there a circuit change needed to accomplish what I need?
Terry Smith
