USB host and device re-configure

[kudjung]

Hi All,

We have a controller that can be configured as either Host and Device in software, not an OTG, but it can configure either way in software.
We want to implement the feature on our usb port so that i can be configured as either Host or Device.

The problem is on the different Vbus cap requirement for Host and Device.
Host require more than 120 UF but Device require less than 10 UF.

Any one can suggest a circuit that I can switch appropriate capacitor in and out of the USB VBUS. Note that it's to be pretty low impedance and has necessary protection since this is a usb port.

Thanks in advance.
KJ.

 

[FvM]

I don't see that host VBUS generally requires 120 µF capacitor, that sounds like a specific application circuit for your device. Having a large capacitor connected to VBUS is rather unwanted, proper overcurrent protection is preferred for USB hosts. Nevertheless, if your design is committed to the said 120 µF capacitor, MOSFET switches are surely an option.

 

[kudjung]

Hi FvM,

The 120 UF cap is recommended by the usb spec. So you think this is not necessarily.
Yes, FET switch is probably and option.

Thanks,
KJ