Specifications

12
1-800-927-9474
20-19
ConverterPAC Functional Descriptions (cont)
Trim (J2)
The Trim pin on J2-1 may be used to control the output voltage. It is referenced to the –Sense
pin on J2-3. For DualPACs, the Trim pins are available on connectors designated as J2A-1 and
J2B-1 for outputs A and B, respectively.
Trimming is accomplished by using the techniques shown earlier in Section 5, Output Voltage
Trimming. These techniques show how a potentiometer placed external to the power supply
may be used to adjust the output voltage (Figure 24, below). Alternatively, a digital-to-analog
converter (DAC) may be used to program the output voltage from 50% to 110% of nominal as
the DAC output is controlled from 1.25 to 2.75Vdc.
MegaPAC Mechanical Considerations
The MegaPAC Family may be mounted on any of four surfaces using standard 8-32/M4 size
screws. The chassis comes with four mounting points on each surface; maximum allowable
torque is 20 in.-lbs. The maximum penetration is 0.15 in (3.7 mm).
When selecting a mounting location and orientation, the unit should be positioned so that air
flow is not restricted. Maintain a 2" minimum clearance at both ends of the MegaPAC and route
all cables so that airflow is not obstructed. The standard unit draws air in at the fan side and
exhausts air out the load side. If airflow ducting is used, pay attention as sharp turns could
present back pressure to the MegaPAC. The fan moves approximately 30 CFM of air (38 CFM
for Three-Phase MegaPAC).
(Remote Sense)
Load
(Local Sense)
+P +Out
J2-2 +Sense
J2-3 -Sense
-P -Out
Use 20-22 AWG Twisted Pair Wires
Figure 23.
Sense Leads
Figure 24.
External Trim
(Remote Sense)
Load
+P +Out
J2-2 +Sense
J2-3 -Sense
-P -Out
Use 20-22 AWG Twisted Pair Wires
10K
2.5V
Ref.
+
J2-1
R6
R8
R7
To Error
Amplifier
MegaPAC™ Family AC-DC, DC-DC Switchers