8.2.2 Output Ripple Control

High frequency applications of the LM25011 or LM25011A are likely to require more ripple voltage than is internally generated across the R_S resistor. Additional ripple can be supplied to the FB pin, in phase with the switching waveform at the SW pin, for proper operation. The required ripple can be supplied from ripple generated at V_OUT, through the feedback resistors, as described in Option A: Lowest Cost Configuration. Option B: Intermediate VOUT Ripple Configuration and Option C: Minimum VOUT Ripple Configuration use one or two additional components to provide ripple at the FB pin with lower output ripple at V_OUT.

The amount of additional ripple voltage needed at the FB pin is typically in the range of 30 mV to 150 mV. Higher switching frequencies or higher inductor values (less ripple current) require more external ripple voltage injected at the FB pin. Insufficient ripple voltage will result in frequency jitter. For a particular application, add only as much ripple as needed to stabilize the switching frequency over the required input voltage.