Berkeley Nucleonics Corporation
2955 Kerner Blvd., San Rafael, CA 94901 ° Tel (415) 453 9955 ° Fax (415) 453 9956 ° www.berkeleynucleonics.com
5.6 Internal and External Current Setpoint
In internal mode, the potentiometer labeled Current Set controls the output current
amplitude. 0 A is full counterclockwise. The output current setpoint monitor may be
used to set the output current without applying a pulse to the laser diode.
The external current setpoint (J2 Pin 4) allows the user to apply an external
voltage to the potentiometer circuit. The on-board potentiometer then can be used
as a range scaling potentiometer. To use this feature, the Current Set
External/Local jumper must be set to the External setting (see Figure 2). If the
jumper is set to the Local setting, this input is not used.
For example, to use 0-10 V input and scale the output accordingly, the
potentiometer may be adjusted to correlate the maximum output current to 10 V
maximum input. In the local mode with the unit enabled and the gate input held
low, set the potentiometer to 0 A output, and then change the jumper to External
Mode. Apply the maximum input voltage desired to the Current Setpoint Input (i.e.,
10 V). Then slowly adjust the current setpoint potentiometer until the desired
output current is obtained on the Output Set Point Monitor.
DO NOT OPERATE
OR PULSE THE UNIT INTO AN OPEN OR HIGH IMPEDANCE LOAD WHILE
MAKING THIS ADJUSTMENT
.
The output current may be monitored using the
internal monitor on J2 pin 6. This allows the user to scale the output current to any
analog voltage program up to 20 V.
5.7 Leading Edge Risetime Control Potentiometer
The PCO-6131 features a user-adjustable variable rise time control. This feature
allows the user to adjust the rise time within a range of <30 ns to >2.5 µs by
means of the PCB-mounted potentiometer (see Figure 2), to optimize the driver’s
rise time for the user’s application. In applications in which the laser diode or
interconnection between the driver and the diode is somewhat inductive, the fast
rise time of the PCO-6131 may induce ringing on the leading edge of the pulse.
The rise time may be slowed down using the variable rise time control to minimize
or eliminate this ringing.
Full counterclockwise is the fastest rise time, and full clockwise is the longest rise
time. Please note that this feature does not affect the pulse fall time.
5.8 Indicator LEDs
Several LEDs on the driver logic board may be used for verification of functionality
and for troubleshooting. The LEDs and their function are listed below: