ZED-F9P-Integration Manual
UBX-18010802 - R02
5 Hardware description Page 74 of 114
Advance Information
USB suspend is not supported.
USB bus powered is not supported.
It is important to connect V_USB to ground when the USB interface is not used in an
application.
Figure 48: V_USB connected ground if not used
There are additional hardware requirements if USB is designed in to be used:
In Self Powered Mode the receiver is powered by its own power supply. V_USB is used to detect the
availability of the USB port, i.e. whether the receiver is connected to a USB host.
• Pin 38, V_USB needs to be powered by a separate LDO enabled by module VCC and supplied by
the USB host.
• A pull down resistor is required on the output of this V_USB LDO
• V_USB (pin 38) requires a 1 uF and a 100 nF capacitor right next to the pin to ensure correct
V_USB voltage detection
• Pin 39 is USB_DM. Pin 40 is USB_DP
Figure 49: ZED-F9P V_USB supply
R11 = 100 k
Ω
is recommended.
In USB self-powered mode, the power supply (VCC) can be turned off and the digital block is
not powered. In this case, since VBUS is still available, the USB host would still receive a signal
indicating that the device is present and ready to communicate. This should be avoided by disabling
the LDO (U1) using the enable signal (EN) supplied by the ZED-F9P VCC LDO. Depending on the
characteristics of the LDO (U1) it is recommended to add a pull-down resistor (R11) at its output
to ensure VDD_USB is not floating if the LDO (U1) is disabled or the USB cable is not connected i.e.
VBUS is not supplied.
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