There are 2 different units, one dedicated to the payload interfacing and control, and the other to the platform, the PLDIU and PFDIU respectively. The architecture foresees two identical units from a physical point of view, each able to host 14 modules. These modules are stacked and inserted into a backplane that distributes the internal communications bus. The unit is consolidated, from a mechanical point of view, by a baseplate, end plates and top cover. An external Bus Bar distributes the main power bus (100v). The development of the unit implements a number of features to ensure full physical segregation between nominal and redundant chains.
The 2 central modules, called STUB, are identical and provide:
- 1553 interface to the external system
- Power supplies for all of the internal power needs as well as certain functions such as telecommand generation, motor driver supplies and sensor supplies.
- Management, command and control of the PxDIU through an internal CAN bus.
To each side of the nominal and redundant STUB modules are up to a total of 7 + 7 functional modules containing all of the functions necessary for: the distribution, protection and monitoring of the 100V main bus power to user equipment; distribution, protection, switching and monitoring of heater power; driving and control of solar array deployment and rotation; chemical propulsion command and control; reaction wheel interfacing; Li-Ion monitoring, and control of cell bypass and cell balancing elements; generation and management of an external CAN bus for future payload needs.
The overall dimensions are 451 x 521 x 224 mm3 (L x W x H) while in the baseline configuration the mass is 28kg for PFDIU and 32kg for the largest PLDIU version.