User's Manual

22 P330 Data Sheet / User Guide
DRAFT
Fig. 4-9: J7 User Serial pinouts
4.3 Powering and Grounding the Unit
4.3.1 Powering the P330 through the USB Power Jack vs Locking &
Mezzanine Connectors
The P330 can be powered in three different ways: through the USB power jack, through the Locking
Connector or through the mezzanine connectors. The user should select one and only one means of
powering the unit. While it is physically possible to power the unit through all three means
simultaneously, this is a very bad practice and should be avoided. Connecting multiple power
sources at different voltages can result in damage.
Two different Grounds are provided: Digital Ground and Supply Ground. In principle Digital
Ground should be used for signal lines and Supply Ground should be used for main power ground. In
practice, the main value of the multiple ground lines is to guarantee a low impedance path to ground.
4.3.2 Reverse polarity protection
The power input (VCC_Main) is reverse polarity-protected and can be driven by any voltage between
5.0 and 48 volts.
4.3.3 Two means of Powering the P330
There are two techniques for supplying power to the P330. One can connect and disconnect the
power connectors or one can power the board continuously and use the Power_Enable_H pin on the
J10 User Mezzanine connector to turn on and off the P330 main power regulators. This capability
gives the user the opportunity to do a hard reboot of the P330 board without needing to physically
break a supply connection.
4.3.4 Chassis Ground
The P330 is provided with a chassis ground through one of the six mounting holes. Each of the six
mounting holes is copper plated on the top, bottom, and inside of the hole. The mounting holes are
not covered with silk screen. These holes are not connected to any ground planes or signals of any
sort. The one exception to this rule is connected to Digital_Ground through the parallel combination