Thanks for your support.
ADUM4160 use as UFP in my application, it’s only a USB device, my customer is host which supply 500mA max, we use USB2.0(Type A) full speed communication between host and device. The input capacitance is related to the inrush current pulses and overshoot on VBUS. I have some concern about it.
1.If the input capacitance on VBUS is 0.1uF, the overshoot on the VBUS is large when hot swap.
2.If the input capacitance on VBUS is 4.7uF, the overshoot on the VBUS is small, but there will be generated some inrush current pulses on VBUS when hot swap the cable, the current pulses width are less than 10us. the inrush current pulses are more than 1.5A. The inrush current pulses seem to exceed 500mA,The host can supply 500mA max. After 2ms, the inrush current pulses are disappear, does the inrush pulses can meet the USB 2.0 standard?
Is there any requirement about the input capacitance on VBUS in the USB 2.0 standard as a UFP/USB device? The input capacitance on VBUS is 4.7uF. Is this correct? Could you help to confirm.
Look forward to your reply, thank you.
The allowance for capacitance on the power lines is actually quite large. It is there to allow the inrush current without dropping the bus voltage due to large loads being added to the Bus. As you can see from the table in the standard, downstream facing ports are required to have 120uF of bypass and upstream facing ports as much as 10uF
I recommend that you refer to the USB2.0 standard section "188.8.131.52 Inrush Current Limiting" for further information and recommendations.
The way I understanding is that the power distribution is built to absorb these inrush currents without pulling the bus down more than 330mV.