SLLSFC6B November 2021 – July 2022 ISOUSB111
Figure 10-1 shows an application for isolating a host or a hub using ISOUSB111. In this example, on the microntroller side, V3P3V1 and VBUS1 are together connected to an external 3.3-V supply. On the connector side, the VBUS from the USB connector is connected to VBUS2 and the V3P3V2 supply is generated using the internal 3.3-V LDO.
Decoupling capacitors are placed next to ISOUSB111 according to the recommendations provided in the Power Supply Recommendations section. An isolated DC-DC converter (such as the SN6505) is to provide power to the VBUS using the 3.3-V local supply. Note that, for a host or hub, the USB standard requires a 120-μF capacitor to be placed on the VBUS so as to be able provide in-rush current when a downstream peripheral is attached. In addition, a 100-nF capacitor is recommended close to the VBUS pin to handle tranisent currents.
ESD diodes with low capacitance and low dynamic resistance, such as PESD5V0C1USF, may be placed on D+ and D- lines. A ferrite bead, with dc resistance less than 100 mΩ, may be optionally placed between VBUS pin of the connector and the VBUS pin of ISOUSB111, as shown in the figure, to suppress transients such as ESD.