BCI Advisor, Service Manual

Page: 41 / 58

Chapter 3: Block Level Description
Advisor
®
Service Manual 3-9
Main Board - Isolated Power Supply
The patient connected side of the main board where all the instrumentation, A/D converter, and DSP controller
resides is electrically isolated from the rest of the system by an isolation barrier. An isolated power supply
supplies power across the barrier. The isolated power supply converts the +12V supply generated by the power
supply to +5V, ISO_+POWER and ISO_-POWER. The isolated power is then regulated down to +5ISO, ANA+5,
ANA-5, +3.3ISO, and +18ISO.
The supply is designed to run at a constant frequency of 115kHz. The non-isolated side of the board generates
this clocking signal.
Main Board - Isolated Communications
The analog section to digital section communications is provided across the isolation barrier using optocouplers.
Five data lines cross the isolation barrier, they are ~REST, SpO
2
_RX, DSP_RX, SpO
2
_TX, and DSP_TX. The ~RESET
line is used to reset the DSP and the SpO
2
board, U55. Communication between the main processor and the
SpO
2
board is done with SpO
2
_RX (U54) and SpO
2
_TX (U51). Communication between the main processor and
the DSP is done with DSP_RX (U52) and DSP_TX (U50).