minimum capacitance for vicor module power supply?

[treez]

Hello,
We are doing a 1V5, 160A power supply as in the attached pdf.
We are using Vicor Power modules.
We must use the absolute minimum capacitance (the purple ringed capacitors) . How can we assess what is the minimum capacitance that we can use from a transient response viewpoint?…I believe the app notes don’t give enough data and we would actually need to build it and do transient response tests…do you agree?
After all, there is no data on the crossover frequency of the P024T048 module with “x” amount of output capacitance and therefore we must build and test.?

P024T048T12AL power module
http://www.vicorpower.com/products?productType=cfg&productKey=P024T048T12AL

VTM48ET020T080A00 …fixed ratio voltage converter
http://www.vicorpower.com/products?productType=cfg&productKey=VTM48ET020T080A00

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And this is related to the above....concerning "Feedback loop bandwidth increase of cascaded SMPS converters?"

Figure 1, Page 2 of the P024T048T12L power module datasheet (below) shows a setup involving a SMPS which comprises a regulation stage followed by an “electronic transformer” voltage down converter stage. Page 2 of this datasheet states that this setup gives “bandwidth and speed advantage“

Why is this?

Since when did cascading a regulated SMPS with a fixed conversion ratio voltage converter mean you can get faster feedback loop bandwidth?

P024T048T12AL power module datasheet
http://cdn.vicorpower.com/documents/datasheets/24V_48V_120W_PRM.pdf

VTM48ET020T080A00 …fixed ratio voltage converter datasheet
http://cdn.vicorpower.com/documents/datasheets/VTM48E_020_080A00.pdf

 

[Easy peasy]

certainly you will needs loads of output C @ 1v5 160A, then you will also need loads of C on the input side to make the system stable, too little C on the input is a recipe for uncontrollable oscillation...

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the amount of o/p C is set by the di/dt in the choke and the desired level of ripple V on the o/p, then transient step loads can be considered to determine what the step drop in Vo will be for worst case step load.