redundant power supply for non ATCA blades chassis.

TPS2456 would be a good choice, but note that the ORing is via a comparator method and may take a bit more to get some sharing.  Another posibility is 2 x TPS2410 plus TPS24710/20.

To get sharing, you will have to build some active balancing into your supplies.  http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&familyId=469&uiTemplateId=NODE_STRY_PGE_T&paramCriteria=no

The output capacitance is quite large.  Pay attention to the precharge/inrush phase of operation with regards to the hotswap MOSFET control method, and SOA.  In general, the NexFETs have good performance (are rugged) in linear operation.  http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&familyId=1941&uiTemplateId=NODE_STRY_PGE_T

Thanks Martin

assuming that current sharing is not relevant, what is the difference between the 2 chip solution of the TPS2456 and the 3 chip solution of the TPS2410+TPS24710 ?

The full solution of oring +sharring is great but still tricky and requires better understanding; can you please recommend of set of evaluation boards of TI which will demonstrate, and later be a starting point for a design which answers all needed requierment of the design (sharing, oring, capacitive load, 25A) ?

Thanks in advance and happy new year.

EVM documentation is accessed from each product's web page.  For example this page is accessed from the TPS2456 page:  http://www.ti.com/tool/tps2456evm

Opening the User's guide get you a schematic, BOM,  and typically the layout.

The TPS2456 is a dual channel EVM, as are the TPS2410/12.  The TPS24710 is a single by nature.  All of these will have to be hacked one way or the other if you want to test at your currents and output loadings.

I am not as familiar with the sharing.

You should use your local FAE to help determine modifications if necessary.  The next resource is one of the Applicaitons engineers who moinitor this forum.  Your TI sales person also has access to resources for customer designs.