Vicor Constant Current (CC) Demonstration Board - Manual (Page 6)

UG:007 vicorpower.com Applications Engineering: 800 927.9474 Page 6
2.2 Mounting a Heat Sink
A pushpin VI Chip heat sink is included with the CC demonstration board to allow extended
bench top testing at full power and lower airflow.
The PRM is equipped with an over-temperature shut down feature. Please refer to the data
sheet for more details.
2.3 No Load Connection
The CC demonstration board relies on the feedback provided by the current flowing through
the sense resistor (R33). If no load is connected to the module output the CC loop will detect a
no-current flow and will steer the SC pin accordingly to the maximum value. The output
voltage of the PRM will be driven to its highest set point. The resistor (R27) can prevent the
PRM from going into an output over-voltage fault during this condition by limiting the
maximum PRM output voltage. The PRM is equipped with over-voltage protection. However, if
the circuit drives the PRM into over-voltage with no load, the PRM may be damaged. Please
refer to the appropriate section for guidelines on properly setting the maximum PRM output
voltage.
2.4 VTM Shut Down
The PRM initiates a VC pulse at start up for the downstream VTM. The VC pulse is used to
synchronize the output of the VTM with the PRM output voltage. If the PRM detects a fault
condition, it will initiate the 12 V, 10 ms pulse to the downstream VTM. Adjusting the (R10)
counterclockwise to limit the output current will drive the PRM output voltage low. It is
possible to manually trigger the under-voltage mechanism where the PRM goes into fault
condition as shown in Figure 6.
Figure 5
Typical Heat Sink