FNP1500/1800 Front-Ends
& FNR-3 Power Shelf Data Sheet
Synch Start-up Connection Between Shelves
The following connection between the shelves is required to achieve a parallel operation. The synch-start circuits
inside the shelves inhibit all power supplies until the last one has recovered from its overcurrent condition and then
synchronize the restart of the outputs.
Synch Start-up Circuit Description
Description
Pin
Location,
Definition
Type
Low level
High level
V max
I max
Auxiliary power +12 V
(Output 2)
26
Vo2+, Aux output, insulated from main output
Logic_GND ,Internally connected over 10 ꢀ to
Vo2-, ( Auxiliary power ground (Output 2))
28
Logic ground
Output inhibit_A
PSU 1-3
<0.8 V
>2.0 V
10 V
3.5 mA
Inhibit_A ,Active low (DC-DC stage off)
Referenced to Logic_GND
12
<7V off
> 9V
15V
The synch_start pin is connected to the
overcurrent signal of the PSU1-3. In the
case of an overcurrent shutdown, this
signal goes high.
R5
10mA
Synch. Startup 1
PSU 1-3
(at PSU)
Referenced to Vo1-
Synch. Startup_A
Sync_start_A , Active high
The signals of several racks can be
connected together in such a way that all
supplies will be inhibited until the last
supply has recovered from its
overcurrent condition.
Rack FNR-3-12G &
Rack FNR-3-48G 1-N
10
Pin on the D-Sub
connector on the
backplane
Referenced to Logic_GND
NOTE: The Sync-Start pins can be wired together only if the power supplies are connected with a minimal voltage drop on power ground as
achieved on a backplane with massive copper bus bars. If there is a less ideal connection, it is recommended to use an opto-coupler for each
unit (IC1, D3, D2).
MCD10074 Rev. 1.2, 15-Apr-10
Page 14 of 17
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