USB Audio 2.0 Reference Design, XS1-L1 Edition Hardware Manual (1.0) 10/18
10
Power
The board is a high-power bus-powered USB device. This means all the power used
by the board is derived from the nom5V VBus supply from the USB connector
and that the device will use more than 100mA from the VBus line when configured.
The board will use approximately 150mA when fully configured and operating.
Simple Low drop out (LDO) linear regulators are used to generate the global 3.3V
supply and the 1.8V supply required by the USB3318 USB transceiver.
A low noise LDO regulator is used to generate the analogue supply for the Audio
CODEC. The CODEC offers higher audio performance at higher supply voltages so the
voltage for this supply is set at 4.3V. This allows some headroom between the 4.5V
minimum VBus voltage and the approx 100mV dropout of the LDO + RC pre-filter.
A low cost buck switching regulator is used to generate the 1.0V core supply for
the XS1-L1. A ferrite bead is used on the +5V VBus input to prevent switching noise
propagating down the USB cable.
When the board is correctly connected to a USB source the USB Power LED is illumi-
nated.
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