Can the input capacitance for the MAX17270 be reduced from 10uF to 4.7uf?

The MAX17270 will work with a 4.7uF input capacitance; however, here are some considerations that you must be aware of to do this:
 

1. The MAX17270 (and other DCM SIMOs) operate by charging the inductor to a programmed current limit (IPK) during the charge cycle and discharging the inductor into the output during the discharge cycle.
   1. The higher the programmed current limit is, the more the ripple will be on the input.
   2. The choice to reduce the input capacitor should be followed with a reduction of IPK as well. Of course, reducing IPK will reduce the overall available output current that can be pulled from the SIMO.
2. The MAX17270 has a minimum input operating range of 2.7V (min) and UVLO falling threshold of 2.45V (typical)
   1. It is possible that with a large enough ripple at the input, the UVLO circuit could be triggered even though the input DC voltage reads 2.7V. This would prematurely trigger UVLO, especially during heavy loads.
3. From our bench testing, we have done line transient tests where we swing the input voltage of the MAX17270 while the part is under operation to see how the outputs get affected.
   1. This test is done with the input capacitor removed and represents an extreme case.
   2. The scope shot shown on the top left of page 11 datasheet shows the input swinging 1V. The outputs here all move <50mV.