Grounding And Power; Grounding; Voltages And Power Supplies - Keysight N9912A Service Manual

Theory of Operation

Grounding and Power

Grounding and Power

Grounding

Each printed circuit board has a single ground plane. The ground planes on the
A4 RF board and A5 system board are connected via the common shields at
multiple points. The ground plane on the A3 front panel interface board is
connected to the ground plane on the A5 system board.
There are no separate grounds in the analyzer. There is no "star" ground point
in the analyzer.
Batt Neg and Ext DC neg are connected to the A5 system board ground plane.
The A2 LCD assembly has two separate grounding circuits: the LCD power and
control circuits and the backlight LED's.
— The LCD power and control circuits share a ground that is connected to the
— The ground for the backlight LED's is connected to the ground plane on the

Voltages and Power Supplies

The following power supplies exist within the analyzer:
— Digital 5 volts—generated from Unreg DC on the A3 front panel interface
— Digital 3.3 volts—generated from Unreg DC on the A3 front panel interface
— Analog supply voltages—seven separate voltages generated from Unreg DC
— LCD backlight voltage—generated on the A3 front panel interface board
— Power for the System Monitor circuit—3.3 volt circuit powered from Ext DC
— Unreg DC—from Ext DC or Batt +, 21 volts max.
— Ext DC—from external Power AC Adapter, nominal 15 volts, acceptable up
— Batt + —from main battery, nominal 12 volts.
All voltages except Ext DC, Batt +, and the System Monitor power can be
turned on/off within the analyzer. Refer to
page 5-10
5-16
ground plane on the A5 system board.
A3 front panel interface board.
board, controlled by the System Monitor on the A5 system board, and used
on the A3, A4, and A5 boards.
board, on/off functions controlled by the System Monitor on the A5 system
board, and used on the A2 LCD assembly and A3, A4, A5, and A6 boards.
on the A5 system board, on/off functions controlled by the System Monitor
on the A5 system board.
from the digital 5 volt supply voltage.
or Batt +, whichever is greater. Used on A5 system board only.
to 19 volts.
for more information.
"Power Management Circuitry" on
Keysight N9912A Service Guide