Specifications

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1-800-927-9474
16-2
Functional Description (cont)
The converters are enabled 50 milliseconds after the thermistor bypass switch is closed.
Bus-OK is asserted after an additional 50 millisecond delay to allow the converter outputs to
settle within specification.
Power-Down Sequence. (See Figure 2.) When input power is turned off or fails, the following
sequence occurs as the bus voltage decays:
Bus-OK is deasserted when the bus voltage falls below 210Vdc.
The converters are disabled when the bus voltage falls below 190Vdc. If power is reapplied
after the converters are disabled, the entire power-up sequence is repeated. If a momentary
power interruption occurs and power is reestablished before the bus reaches the disable
threshold, the power-up sequence is not repeated.
Off-Line Supply Configuration
The VI-ARM maintains the DC output bus voltage between 200 and 375Vdc over the specified
input range, which is compatible with Vicor VI-260 series and VI-J60 series DC-DC converters,
as well as next-generation 300V input Vicor converters. The VI-ARM automatically switches to
the proper rectification mode (doubled or undoubled) depending on the input voltage,
eliminating the possibility of damage due to improper line connection. The VI-ARM-C12 is
rated at 500W in the low range (90-132Vac input), and 750W in the high range (180-264Vac
input). The VI-ARM-C22 is rated for 1000W and 1500W for the low and high input ranges,
respectively. Either of these modules can serve as the AC front end for any number and
combination of compatible converters as long as the maximum power rating is not exceeded.
Strap (ST) Pin. In addition to input and output power pin connections, it is necessary to
connect the Strap pin to the junction of the series holdup capacitors (C1, C2, Figure 3) for
Applications Manual
400
300
200
100
0
90–132V
AC Line
Output
Bus
(Vdc)
Strap
PTC
Thermistor
Bypass
Converter
Enable
Bus OK
50ms
50ms
Power
Up
Power
Down
4.1
1.1
2.1
3.1
5.1
2.2
1.2
Figure 2.
Timing diagram:
power up/down sequence
4.1
5.1
1.2
2.2