Datascope Passport - Mindray
Datascope Passport - Mindray
Datascope Passport - Mindray
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XE-50 Recorder Interface Board Theory of Operation<br />
2.9 XE-50 Recorder Interface Board<br />
2.9.1 Cooling Fault<br />
The Cooling Fault signal is driven by an FET (Q2), to the CPU to alert the CPU that a cooling<br />
fault has occurred. A “Cooling Fan Failure” message will be displayed on the unit. The fault<br />
can be cleared, if there is no obstruction in the fan, by cycling system power. In normal fan<br />
operation, a pulse train is present at the SENSE pin. A missing pulse detector monitors this<br />
pin during fan operation. A stalled, open or unconnected fan causes the TC646 to trigger its<br />
startup timer once. If the fault persists, the FAULT output goes low, and the device is latched in<br />
its shutdown mode. The Cooling Fault signal is also generated if there is an over-temperature<br />
condition. That is, a temperature rise above the point where the fan's PWM control signal is<br />
at 100%. A “Cooling Fan Failure” message will be displayed on the unit, but no action is<br />
necessary if the temperature normalizes.<br />
2.9.2 Fan-Fault Sense<br />
The SENSE input (U2 pin 5) is connected to a resistor divider network (R5 & R30) to scale<br />
down the tach pulses from the fan. During normal fan operation, a brief interruption in the<br />
fan current generates pulses into the sense resistors network. If the device is not in Shutdown<br />
mode, and pulses are not appearing at the SENSE input, a fault exists. The Sense Network<br />
shall scale-down the pulses that will meet the requirements of the TC646 of 90mV minimum<br />
at pin 5.<br />
2.9.3 Power Filtering<br />
Power filtering of the recorder logic 5VDC is provided by L1 together with C5 and C6. This<br />
circuit provides a low pass filter to reduce noise introduced into the system power. Since the<br />
load is digital logic, the current peaks are minimal. This board provides the power filtering<br />
for the recorder motor and print head. It must suppress the high current peaks from affecting<br />
the power supply and power distribution within the system. The suppression reduces these<br />
peak loads to less than the recorder in-rush current with a maximum voltage ripple of<br />
0.5VDC.<br />
Capacitor C7 is for the purpose of reducing induced PWM switching noise. The value of this<br />
capacitor depends on the fan current consumption. Therefore, this capacitor value may be<br />
adjusted after lab measurements are analyzed. A provisional capacitor (C16) is included as<br />
a placeholder with a different footprint to further aide in the elimination of the fan's<br />
acoustical noise, if required.<br />
2.9.4 XE-50 Interface<br />
J4 Interfaces the XE-50 Recorder to this Module. Data is transferred serially to and from the<br />
recorder when it gives the indication that it is ready to accept data. The signals SINEN* and<br />
RDY* are ANDed together to produce the REC_CTS*, which is processed by the CPU for<br />
data flow-control.<br />
2 - 34 0070-10-0441 <strong>Passport</strong> 2®/<strong>Passport</strong> 2 LT Service Manual