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System Overview
The VNUS RFG2 RF Generator supplies and controls the RF energy delivered to the RF Device . The RF
Generator measures and displays RF output Power, load Impedance (ClosureRFS only), and elapsed time
of RF delivery . The RF Generator also interfaces with a sensor in the Device to provide a continuous
display of measured Temperature during RF delivery .
The RF Generator consists of five main sections: UI Board, Front Panel Interface Assembly (FPI), RF Board,
MMC/USB Assembly, and AC Power Board . A commercially available, medical grade, switching power
supply is used to provide low-voltage power to supply the Generator's internal circuitry .
The major functional blocks of the VNUS RF Generator electronics are presented below in Figure 3 .
AC Power
AC Inlet
USB Port
Switch
AC Power Board ECI
AC Inlet ECI
Speaker
120-
ECI
240VAC
USB/MMC
Signals
Speaker
Analog
Audio
UI Control Board ECI
Display
Backlight
Switch
Power
Power
Press
Indicator
Display
Signal
Control
Control
Interface
Front Panel Electronics ECI
RF Switch ECI
RF Power
RF Power
Display
Switch
Indicator
Keypad
Figure 3: Block Diagram of the VNUS RFG2 Radiofrequency Generator
UI Board
All User Interface controls and indicators are managed and/or generated by the UI control circuitry . The
UI Board is the large (app . 20"x5") PCB mounted vertically inside the chassis directly behind the LCD
display . It controls all electronics that handle basic system operation and User Interface control . It also
contains the RF Switch Circuitry for turning off/on RF power . In addition, the LCD Backlight Inverter
(small 1"x4" PCB) is mounted to the UI Board . It is controlled by the UI Board and used for powering the
6 . 4 " LCD display CCFL backlight tubes .
2
Memory Card
Port
Fan MCI
Fan Power
24VDC
Enclosure MCI
RF Board ECI
RCIP
Keypad
Backlight
Device
Power
Keypad
Connector
Power
On LED
Press
Signals
Signal
Power
RF Output Connector
ECI
Power On
Display
Device Connector
LED
VNUS Radio Frequency Generator
Front Panel Interface Assembly (FPI)
The Front Panel Interface Circuitry consists of 2 circuit boards (the UI Horizontal and UI Vertical keypad
boards), and the RF switch circuitry, which is included on the UI board . The UI Horizontal and UI Vertical
PCBs (also referred to as the keypad boards) contain the 6 general purpose keys and backlighting below
(UI Horizontal Board) and to the right (UI Vertical Board) of the LCD display (as viewed from the front of
the Generator) . The RF Switch circuitry (contained on the UI Board) provides the switch and colored-
backlighting for the RF on/off switch located on the right of the FPI (as viewed from the front of the
Generator) .
RF Board
The RF Generation Board generates a RF sinewave at 460 . 8 kHz, and provides the UI Board with
measurements of delivered voltage, current and power . The RF Board controls the RF output by enabling
RF generation and by controlling the amount of voltage delivered by the RF Board . The RF Board is the
large (app . 8"x6") PCB mounted horizontally in the bottom of the chassis on the right side (as viewed
from the front of the Generator) . The RF Board controls all electronics that generate the RF power used
to drive the device . Additional safety signals and control are provided by the UI Board through the 16
position IDC cable that runs between the UI and RF board .
MMC/USB Assembly
The MMC/USB Assembly is incorporated on the AC power board and refers to all MMC/USB related
components . These components primarily consist of an MMC slot, a USB host controller, and filter
components out on the AC Power Board . The UI processor (on the UI Board) controls the MMC and USB .
The UI processor is connected to the components on the AC Power Board via the 14 position IDC cable in
the left front corner (as viewed from the front of the Generator) .
AC Power Board
The AC Power Board is the large (app . 8"x6") PCB mounted horizontally in the bottom of the chassis on
the left side (as viewed from the front of the Generator) . The AC Power Board controls the AC/DC power
supply (and related circuitry) that generate 24 Volts to drive the system . The AC Power Board also
monitors over-temperature conditions and drives the fan circuitry . The MMC/USB card slot, connector,
and filter circuitry are also contained on this PCB .
Isolation Barrier
For the patient safety, an electrical isolation barrier is designed into the RF Board . The Isolation Barrier
separates the Patient Connected side and the Non-Patient Connected side . There is 4000 VDC separation
between AC Mains, Functional Grounds, Earth Ground and all exposed surfaces from patient contact . All
devices (relay, transformer and opto-isolators) also have a minimum of 4000 VDC isolation between
inputs and outputs .
The instantaneous voltage and instantaneous current of RF Output are fed back across the isolation
barrier and input directly to an ADC .
Two power supplies, a +5V and a +2 . 5 V supply are on the patient side of the isolation barrier . The
capacity of the +5V supply is 50mA .
The isolated 5V supply is the source for the +2 . 5 V supply . The output capacity of 25mA . It is used in the
Patient Connected Circuitry .
Service Manual
3
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