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

RF Analyzer
N9912A

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 ground plane on the A5
system board.
• The ground for the backlight LED's is connected to the ground plane on the A3 front panel interface
board.

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 board, controlled by the System
Monitor on the A5 system board, and used on the A3, A4, and A5 boards.
• Digital 3.3 volts—generated from Unreg DC on the A3 front panel interface 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.
• Analog supply voltages—seven separate voltages generated from Unreg DC on the A5 system board,
on/off functions controlled by the System Monitor on the A5 system board.
• LCD backlight voltage—generated on the A3 front panel interface board from the digital 5 volt supply
voltage.
• Power for the System Monitor circuit—3.3 volt circuit powered from Ext DC or Batt +, whichever is
greater. Used on A5 system board only.
• Unreg DC—from Ext DC or Batt +, 21 volts max.
• Ext DC—from external Power AC Adapter, nominal 15 volts, acceptable up to 19 volts.
• 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 "Power Management Circuitry" on page 5-10

Power Control and Management

Power States
The On/Off Button is used to switch between On, Off, and Standby power states:
Service Guide N9912-90003
for more information.
Theory of Operation
Grounding and Power
5-17