Specifications

Vcc In (J3-4)
The Vcc In on J3-4 is an input that requires +5V either from the J10 Auxiliary Vcc, or from another source. Input
current to this pin is limited by an internal resistor to 3 mA. If the J10 Auxiliary Vcc is connected to Vcc In on J3-
4, then the J10 Signal Ground must be connected to Signal Ground on J3-1.
+Sense/–Sense - J2-2 and J2-3 (See page 10 and 13 for information on Autosense)
The +Sense on J2-2 should be connected to the +Power Out, and the –Sense on J2-3 to the –Power Out terminal.
Do not reverse or leave the Sense pins open. Sense pins can be terminated locally at the output of the power
supply, in which case the power supply will provide regulation at the output terminals. The voltage appearing at the
load may drop slightly due to voltage drop in the power cables. If it is necessary to compensate for voltage drop
along the output power cables, this termination should be made close to the output load. Compensation of up to
0.5V (0.25V per lead) can be obtained. Use twisted pair 22-24 AWG wire for this purpose.
For DualQPACs, the +Sense pins are available on connectors designated as J2A-2 and J2B-2 for outputs A and B,
respectively. –Sense pins are on J2A-3 and J2B-3, respectively. These pins are also duplicated on the power con-
nectors J1A and J1B.
Reminder: Only units with Autosense will automatically operate in Local Sense mode if no sense connections
are made. It will operate in remote sense mode if remote sense connections are made. Units without
Autosense MUST have sense connections (Local or Remote) terminated to their respective output for the
unit to operate properly.
External Trim (J2-1)
Output voltage can be trimmed using an optional factory-installed Trim potentiometer or with the Trim pin (see
Figure 11). The Trim potentiometer is located on the ConverterPAC. If the Trim potentiometer has not been
ordered, the Trim pin must be used. When using the Trim pin, the Trim limits are determined by the DC/DC con-
verter used on the ConverterPAC. Maximum Trim ranges are 10% above the nominal converter voltage and 50%
below the nominal converter voltage (except 10V, 12V and 15V outputs which are 10% below nominal) as meas-
ured from the output studs or output connector of the power supply.
Note: The combined effects of module trim up, remote sense and dynamic load step may cause the module to trip
OVP. (See page 7 for information on restart).
The Trim pin on J2 can be used to control the output voltage. It is referenced to the -Sense pin on J2 and can be
controlled by either a resistor network or an external voltage source. To increase an output voltage above its nomi-
nal, it is necessary to increase the voltage at the Trim pin above the internal reference voltage (Vref). The reverse is
true to decrease an output voltage.
Note: Converters are sometimes pretrimmed at the factory if a nonstandard output voltage is requested. Standard voltages
include 2V, 3.3V, 5V, 10V, 12V, 15V, 24V, 28V, and 48V. If using a nonstandard voltage, or if a ConverterPAC is ordered with a
Trim option, the resistor calculations will differ from those on page 17. Please consult the factory for assistance.
Pg 16 Vicor 800-735-6200 Westcor Division 408-522-5280 Applications Engineering 800-927-9474 Rev. 6/2004
PFC MegaPAC-EL/PFC MegaPAC-High Power Low Noise
(Remote Sense)
Load
(Local Sense)
+P +Out
+Sense
-Sense
-P -Out
Use 22-24 AWG
Twisted Pair Wires
Figure 10. Sense Leads