I am designing a Raspberry Pi shield and it needs to have two separate supplies: one for the RPi itself, and one for the rest of the circuitry (consisting of energy metering ADE7758 chip). I plan on using Mean Well switching mode power supplies. The ADE7758 part of the circuit needs 5V/100mA. The RPi supply needs to provide 2A at 5V.
The concern I have is about the power supply ripple and I am looking for advice on how to calculate the value for the smoothing capacitor or any other method for smoothing the output of the supply. I don't want to plug in a LDO regulator after the SMPS as I don't have enough space on the board. The datasheets of the power supplies specify 150mV and 200mV ripple but do not specify the frequency, so I assume it is 50Hz.
Using the equation for capacitor discharging is giving me unreasonable values if I use Vc = 5.000, starting voltage 5.075V and t = 0.01s: 13.43mF. That is if I want to reduce the 150mV ripple in half.
Edit 1 (as suggested by the comments): Acceptable ripple for the RPi supply is 120mVp-p, and for the ADE7758 power supply is 50mVp-p.
Edit 2: Adding a schematic.