Operator`s manual

Pg. 14 Vicor 800-735-6200 Westcor Division 408-522-5280 Applications Engineering 978-749-3524 or -3525 Rev. 1/99
External Trim (J2-1)
Output voltage can be trimmed using an optional factory-installed trim potentiometer or with the Trim pin (see
Figure 18). 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.
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, 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 below. Please consult the factory for
assistance.
OUTPUT MODULE V
ref
R
TH
VI-200/VI-J00 ≥3.3V 2.50V 10.0 kΩ
VI-200/VI-J00 <3.3V 0.97V 3.88kΩ
2
nd
Generation (Pre-Configured) 1.23V 1.0 kΩ
2
nd
Generation (Customer Configured) 1.23V Consult Factory
Table 2. Module Internal Reference Voltages and Thevenin Resistances.
3 Phase MegaPAC Owner’s Manual
(Remote Sense)
Load
+Out
+Sense
-Sense
-Out
Use 22-24 AWG Twisted Pair Wires
R5
Trim
R6
R8
R7
To Error
Amplifier
R4
20-200Ω
R3
R2
R1
10-300Ω
V
Ref
R
TH
V
2
+
-
V
1
+
-
Figure 17. External Trim