Operator`s manual

Rev. 1/99 Vicor 800-735-6200 Westcor Division 408-522-5280 Applications Engineering 978-749-3524 or -3525 Pg. 13
3 Phase MegaPAC Owner’s Manual
Power Good (J3-3)
The optional Power Good signal on J3-3 is referenced to Signal Ground on J3-1, and indicates the status of the
output voltage. This signal is asserted a TTL “1” when the output voltage is above 95% of nominal. It is a TTL “0”
when the output voltage is below 85% of nominal.
If the Trim option is also used, the Power Good trip points DO NOT track with the trimmed voltage. It is possible
to trim the output below the fixed setpoints of the Power Good circuit and cause a negative Power Good signal.
Power Good Inverted (J3-2)
This is the inverse of the Power Good signal and is referenced to Signal Ground on J3-1.
Signal Ground (J3-1)
Signal Ground on J3-1 is an isolated secondary ground reference for J3 status signals. It is used to provide a refer-
ence point for the Power Good circuitry and is not the same as Earth Ground on input power connector J1.
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 at least one J10 Signal Ground must be connected to Signal Ground on J3-1.
+Sense/–Sense (J2-2 and J2-3)
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 sup-
ply, 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 DualPACs, 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.
Signal Ground
2
Vcc In
4
J3
10K
2.49K
2N2222
2.49K
1
Power Good
3
Power Good Inverted
ConverterPAC
Figure 15. Power Good and Vcc
(Remote Sense)
Load
(Local Sense)
+P +Out
J2-2 +Sense
J2-3 -Sense
-P -Out
Use 22-24 AWG Twisted Pair Wires
Figure 16. Sense Leads