I am prototyping a simple board with several (3 or 2) USB-to-Serial convertors (CP2102), a microcontroller (ATMega32U4), and one USB "output" port to connect using USB cable (in case of only 2 CP2102's). I want to use TI's TUSB2046B USB Hub controller to connect all this devices through a single microUSB input. I don't want to use an external hub to save space and to simplify the final assembly.
The question is about interconnection between USB Hub and on-board devices. The official TI's datasheet is proposed to connect several external components on the each output data lines:
- Series resistor (27 Ohm).
- Capacitor between the TUSB2046B pin and the series resistor (22 pF).
- Pull-down resistor (15 kOhm) after the series resistor
- and a USB ESD protection unit SN75240…
Also datasheet proposes to use a
- Power Management unit (TPS2044).
And also, on the ATMega32U4 side, there should be a
- 22 Ohm series resistor on each data line.
So, what components should I use to connection on-board devices using like a 10 centimetre length data lines?
Of course, I don't need and ESD protection module, but I'm not sure about other components.
There is a particular question about a power management unit. As I understand it tells the USB hub that something is connected to a certain port, and it does not draws too much current. So, I do not need it for on-board devices? Only for my output port, if any?