Specifications

AC OK / Power Fail (J10-11)
This is an active high TTL compatible signal and provides a status indication of the AC input power (see Figure 7
and Connector Pin Identification on page 9). It is capable of sourcing 0.5mA at >3.2V and sink 16mA at < 0.5V.
This signal switches to a TTL “1” when the high voltage bus exceeds low-line condition during turn-on, and
switches to a TTL “0” 3 ms (minimum) before loss of output regulation due to the loss of input AC power. This
signal can be used to warn external control circuits of an impending loss of power.
Auxiliary Vcc +5V/0.3A (J10-9)
The Vcc on J10-9 is an auxiliary 5V regulated power source (see Figure 8 and Connector Pin Identification on
page 9). It is +5 Vdc +/–5% with respect to Signal Ground and can supply 300 mA maximum. It is short-circuit-
proof, but if shorted all outputs will shut down through the Enable/Disable circuitry. The Auxiliary Vcc typically
powers user circuitry or is used with the Power Good circuitry to provide a pull-up reference for the outputs of the
DC Power Good circuit on a ConverterPAC. If used for this purpose, the Signal Ground on J10-10 must also be
connected to the J3-1 Signal Ground pin of the ConverterPAC.
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 out-
put 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 J9.
Rev. 6/2004 Vicor 800-735-6200 Westcor Division 408-522-5280 Applications Engineering 800-927-9474 Pg. 15
PFC MegaPAC-EL/PFC MegaPAC-High Power Low Noise
10K
Signal Ground
AC Power OK
11
+5V
10
J10
2.49K
PN2222
Figure 7: AC OK Power Fail
78M05
Auxiliary Vcc
9
0.1 µF
Signal Ground
J10
10
+5V/300 mA
Figure 8. Auxiliary Vcc
Signal Ground
2
Vcc In
4
J3
10K
2.49K
2N2222
2.49K
1
Power Good
3
Power Good Inverte
d
ConverterPAC
Figure 9. Power Good and Vcc