Designer Reference Manual USB08 Evaluation Board
36 Hardware Description MOTOROLA
Hardware Description
2.4.5 Power Supply
Power can be supplied to the USB08 board by using the USB or via t he
voltage regulator IC3. The change between these options is done by
replacing the jumper JP2. If the jumper is placed in position 2–3 (Bus
Powered), the operating power is supplied by VBus and VGND from the
USB.
If a dc voltage between 8 V and 20 V is fed into the power plug X4 in
jumper position 1–2 (Self Powered), the voltage regulator IC3 supplies
5 V in the case. The solder bridge BR4 on the downside of the PCB (see
Figure 2-3) has to be in position 1–2. Alternatively, if the bridge BR4 is
in position 2–3, a stabilized 5-V power supply can be used to feed VDD
directly.
The voltage regulator IC3 is specified with 1 ampere. Although no
special cooling measures are intended, IC3 is more than sufficiently
dimensioned. The input current of the board, even in the worst case, is
clearly smaller than 100 mA.
A USB hub supplies at least 100 mA. Therefo re, the power su pply of the
board via the USB is possible without any problem. The USB08 board
power input specification should be registered in the device d escriptor of
the USB device (see Section 4. Universal Serial Bus (USB) Interface ).
2.5 Board Layout Figure 2-2 and Figure 2-3 show the components and parts layout, as
well as a general picture of the board.
On the component side, Figure 2-2:
•The jumpers, plugs, push buttons, and LEDs are marked.
•The USB cable is fixed on the board with a cable strap, and the
four line ends are soldered directly to the X5 connection points
(without patch cord). This kind of connection is usual for
low-speed USB devices.
A detailed layout plan of the USB08 board with the names of all
components is shown in Figure 2-3.