UCC28880EVM_616 questions

Now there have some questions about Modified of the UCC28880EVM.

The following is the UCC28880EVM_616 high side buck Evaluation Module.

as I said before, the Specification is like this.

Input Voltage: Battery DC92V (Peak  DC100V)

Output Voltage: 5V

Output Current : 14.77mA in normal operation (Not decided). Less 1mA in sleep mode. Light load efficiency is key index in selection device.

So we need to change some component to optimized for 5V output setting.

Red region: Because of the input side is a battery of a 100VDC, so we can remove R1, D1, D2 L1 and C1. is it right ?

Yellow region : A. because of the input is a 100VDC, we could choose diode D3 and D4 what the Vpp is only need about 200V (Don’t need Vpp=600V in this application), what’s your opinion ? Could you let me know 200V is OK for this application ?

So I choose 3 kinds of alternative Diodes. Please help us to review this and help us to choose a satisfied Diode for this application ?

1. From DiODES

http://www.farnell.com/datasheets/378369.pdf

2. S/D from DIODEs.

http://diodes.com/catalog/schottky___sbr_rectifiers_0723/?filter_1%5B%5D=1&filter_2%5B%5D=&filter_3%5B%5D=&catalog_id=6&order=el_167&filter_type=el_167&filter_cancel=0

3. Ultra Fast diode from DIODES.

http://diodes.com/catalog/fast_super_fast_ultra_fast_recovery_rectifiers_8/?filter_1%5B%5D=18&catalog_id=8&order=2&filter_type=1_pt&filter_cancel=0

B. Output Capacitor C5.

Could we decrease the value of C5?

Blue region :  as we know we could optimized this application of 5V output setting. Could you give me some guide for optimized R2, R3, R4 and C4 to optimized for audible noise.?

Your immediate action is highly appreciated.

Thank you.