*Actual throughput at the system level could be lower due to overheads.
**PCIe trace length in FN990 Family: about 15 mm.
USB 3.1 Interface
The FN990 Family modules include super-speed USB 3.1 Gen 2 with high-speed USB 2.0
backward compatibility. It complies with the Universal Serial Bus Specification, revision 3.1,
and can be used for control and data transfers as well as for diagnostic monitoring and
firmware update.
The USB port is typically the main interface between the FN990 Family module and
application hardware. USB 3.1 needs AC coupling series capacitors on the TX lines in both
directions.
To interface USB 3.1 with the application board controlling the modem, it is necessary to
install a 220 nF capacitor on the USB_SS_RX_P/M lines of the FN990 Family. The series
capacitors are already placed on USB_SS_TX_P/M lines inside the FN990 module.
Figure 13: Connection for USB Interface
Note: The USB signal traces must be carefully routed: minimize trace lengths,
number of vias, and capacitive loading. The impedance value should be as close as
possible to the 85 Ohm differential.
Table 33: USB Interface Signals
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