Valleylab Force FX-8C, Service Manual

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Control Board
4-8 Force FX-8C Service Manual
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 PSD412 (U6) and the PSD413 (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 Cut, Pure Cut, Desiccate 1, and Desiccate 2
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.