TPS53353: TPS53353 VFB problem

Xiao,

Please see the attached pictures for light load and no load condition.  Please see the explanation below including picture as to why in D-CAP the VOUT accuracy is off in DCM.

·        VOUT average is above VREF by half ripple. So, VOUT average is higher with light load (DCM) and lower with heavy load (CCM).

·        During skip mode operation, under discontinuous conduction mode (DCM), the switching frequency is lower than the nominal frequency and the off-time is longer than the off-time in CCM. Because of the longer off-time, the ramp signal extends after crossing 0 mV. However, it is clamped at 3 mV to minimize the DC offset.