HD3SS3220: Capacitors on Tx/Rx

Hi Yamaguchi,

You should not place the AC coupling capacitors on Txp/Txn. The AC coupling capacitors are placed such that HD3SS3220 common is biased by the USB Host and not the USB device or other components connected on the other side (Tx2p/Tx2n, Rx2p/Rx2n).

Hello Sir,

I also have similar question about HD3SS3220 DFP EVM .

- Is these pull down 100K ohm necessary ?  Can I remove it ?

- Datasheet suggest AC coupling Cap is 0.1uF but EVM is 0.47uF , may I know why ?

Many thanks !

Hi,

The AC coupling capacitors of 0.1 uF should be used on the TX pin. The pull down resistors are need to bias the common mode voltage to a appropriate levels. This may be necessary depending on your application. Could you provide a simple block diagram of your application?

Hello Malik,

This application is Desktop PC main board ( DFP only )

Shall we still reserve pull down 100k resistor ? Or just follow Fig.11 connection Tx output AC 0.1uF Cap only ?

Many thanks !