74 Keysight FieldFox Handheld Analyzers Service Guide
Theory of Operation
Grounding and Power
5-
Power Control and Management
Power States
The On/Off Button is used to switch between On, Off, and Standby power
states:
Off
Only the System Monitor and battery control circuits are powered up (if power
is available from the battery or external power).
If the battery is charging, the LED below the On/Off Button slowly flashes
orange with increasing intensity, otherwise this LED is off.
Some battery power is required in the “Off” state. A fully charged battery will
discharge completely in four to six weeks when left in the analyzer.
On
This is normal operation. The On/Off Button LED is steadily lit green.
Standby
Only the digital power supplies are on. The CPU is in a low power state,
maintaining RAM content. The On/Off Button LED flashes yellow briefly every
two seconds.
During normal operation, unexpectedly disconnecting power to the analyzer
(such as removing the main battery when the analyzer is not connected to
external power) should not cause any problems. Simply re-apply power. No
firmware problems are expected. Of course, this does not apply during a
firmware upgrade.
Smart Power Management
The analyzer uses extensive “load switching” to minimize power dissipation.
This is termed Smart Power Management (SPM). There are two motivations for
power management:
— to extend battery run time
— to prevent overheating
Sections of the circuitry are selectively powered down via “load switching”,
depending on the operating mode of the analyzer. Five different sections of the
circuitry on the A4 RF board may be controlled via “load switching”. These
sections are as follows:
For N991xA, N992xA, and N993xA the default state for the Smart Power Management is ON.
For N995xA and N996xA the default state for the Smart Power Management is OFF.
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