Find the power supply output capacitance required to keep the 48 V power supply for the sonar on the MARS Echosounder from browning out when the first ping is transmitted. Previous testing has shown that the charging of the transmitter capacitors on one sonar demands 8 A for 14 ms at 12 V. We’re running at 48 V, so the same power can be delivered at 2 A, but we’re running two sonars, so the demand will be 4 A at 48 V  for 14 ms. The input voltage must not drop below 20 V.

Vbus=48

Ibus=4

deltaT=0.014

deltaV=48-20

c=Ibus deltaT/deltaV

We need at least 2000 µF to supply 4 A for 14 ms while staying above 20 V.

The maximum capacitance allowed by Vicor, according to page 17 of the “Maxi, Mini, Micro Design Guide” is

cmax=(((75/48) (400 (10^(-6))))/48)//N

This is only 13 µF.