Control Board
Principles of Operation
Force FX Electrosurgical Generator C Service Manual 4-9
Power Supply Supervisor Circuit
The power supply supervisor circuit (U14), a MAX691, generates a Reset signal and a
Reset\ signal for the main microcontroller (U5) if the power supply voltage to the Control
board drops below 4.65 V. It also generates a voltage sensitive chip select for the
PSD835G2 (U6) and the PSD835G2 (U3). The low voltage threshold (4.65 V) places U3
and U6 in sleep mode and disables the 2K x 8 external static RAM.
A/D and D/A Conversion
Each 80C562 microcontroller (U5 and U11) contains an 8-channel multiplexed 8-bit A/D
converter. Resolution of voltage and current sense inputs is enhanced by incorporating
gain scaling relays in the sense circuits on the Power Supply/RF board and prescaling
based on the expected input voltage or current values.
An MP7226 quad D/A converter (U15) provides 4-channel 8-bit D/A capabilities for the
feedback microcontroller to output 0 to 5 Vdc analog voltages.
Waveform Generation (T_ON ASIC)
A dedicated 89C54 microcontroller (U9) generates the RF drive waveforms (T_ON\) for
the RF output amplifier on the Power Supply/RF board. The microcontroller functions as
an application-specific integrated circuit, or ASIC, performing an endless series of
repetitive tasks while enabled.
The feedback microcontroller (U11) holds the T_ON ASIC (U9) in a reset state until the
feedback microcontroller detects a valid activation request. After validating the request,
the feedback microcontroller releases the T_ON ASIC from reset and communicates a
4-bit code that represents the generator mode to be activated. The acceptable activation
codes are listed below:
0: Precise bipolar
1: Standard and Macro bipolar
2: Low and Pure Cut
3: Blend cut
7: Desiccate coag
8: LCF Fulgurate coag
9: Spray coag
11:Spark-controlled Blend
12:Fulgurate coag
Codes 4, 5, 6, 10 and A–F are unused.
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