Agilent Technologies FieldFox MW N9913A, Service Manual

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N9927-90003 5-15
FieldFox Analyzer Theory of Operation
Measurement Group
System Monitor (SM) Microcontroller
This is the heart of the analyzer. It is active whenever there is DC power available. The microcontroller
has ultra-low power dissipation. It is sometimes referred to as the “MSP 430”.
The following is a list of some of the functions performed by the SM.
• It monitors the On/Off button on the front panel and responds appropriately.
• It controls the on/off functions of the various power supplies in the analyzer.
• It drives the On/Off button LED.
• It reads battery pack information via the Smart Batt Bus.
• It communicates with the battery charger IC via the Smart Batt Bus.
• It interfaces to the Battery Charger and Manager circuit.
• It interfaces to the Serial Bus for communication with the temperature sensors and ID EPROM’s on
the printed circuit boards.
• It communicates to the A6 SOM board CPU via a serial port, UART.
• It stores the instrument model number and serial number.
USB Hub
This circuitry expands the number of USB ports available to the FieldFox firmware.
Power Management and Power Supplies
Seven different analog supply voltages are generated from the Unreg DC. All of these are used on the A4
RF board and some are used on the A5 System board.
Some sections of the circuitry on the A4 RF board may be switched to low power modes to conserve
power and minimize heat. This is accomplished through load switching. See
“Power Management
Circuitry” on page 5-12 for more information.
The System Monitor controls the on/off functions of the analog power supplies. All are on or off together
except for power sequencing.
This circuitry also monitors the Ext DC input and, if below 10.8 volts or above 21 volts, it disconnects
this input from the Unreg DC.
FPGA
This FPGA:
• provides the interface between the A6 SOM board and the ADC,
• provides miscellaneous interfaces for circuitry on the A4 RF board, and
• communicates with the CPU via the USB interface.