Eco-mode is a feature that automatically reduces the switching frequency at light loads. It takes energy to turn on the power MOSFETs and to operate the integrated circuit. If the quiescent current and switching frequency are reduced during light loads, the overall efficiency will increase. The graph on the right shows a fixed frequency PWM operating at 500kHz. As the load requirement is reduced, the MOSFET driver, gate charge, and quiescent current losses begin to dominate in the efficiency calculation because the IC is still operating and the MOSFETs are still switching even though less power is delivered to the load. For example, at 10mA, the efficiency is around 35% with the TPS5430. With the Eco-mode efficiency plot on the left hand side, the frequency is reduced and the MOSFET driving and gate charge losses are also automatically reduced delivering higher efficiency. For example, at 10mA, the efficiency is now around 70% with Eco Mode.