7.4.3 Advanced Eco-Mode™ Control

The advanced Eco-Mode™ control scheme to maintain high efficiency at light loads. As the output current decreases from heavy load conditions, the inductor current is also reduced and eventually comes to a point where the rippled valley touches zero level, which is the boundary between continuous conduction and discontinuous conduction modes. The low-side MOSFET is turned off when a zero inductor current is detected. As the load current further decreases, the converter runs into discontinuous conduction mode. The on-time is kept almost the same as it is in continuous conduction mode so that it takes more time to discharge the output to the level of reference voltage with a smaller load current. The light load current where the transition to Eco-Mode™ operation happens ( I_OUT(LL) ) can be calculated from Equation 2.

Equation 2.

After identifying the application requirements, design the output inductance (L_OUT) so that the inductor peak-to-peak ripple current is approximately between 20% and 30% of the I_OUT(max) (peak current in the application).