10.7.2 Operation
JPDH is designed to provide TMR I/O packs with adequate 28 V dc power distribution while taking up as little space as
possible. Additional JPDHs can be connected in a daisy-chain arrangement through the unfused J1X connector.
Note The user must provide suitable branch circuit protection when connecting multiple JPDHs. Each pin is rated at 13 A.
The 6-pin J1 connector brings in three separate 28 V dc feeds on three different pins for triple redundancy. The return current
is common among the TMR and daisy-chain feeds and is brought in on the remaining three pins. The following figure
explains how the R, S, and T 28 V dc power is distributed by JPDH to the I/O packs and Ethernet switches.
JPDH Power Flow
JPDH has 24 identical output circuits to provide power to the individual I/O packs. The R, S, and T feeds each provide power
to eight circuits. Each I/O pack circuit includes a positive temperature coefficient fuse device for branch circuit protection.
The board also has three identical unfused output circuits to provide power to each Ethernet switch.
386 GEH-6855_Vol_II GEH-6855_Vol_II Mark VIeS Functional Safety Systems Volume II
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