Control Architecture gives a brief introduction to the LM516x diode emulation (DEM) feature. The converter enters DEM during light-load conditions when the inductor current decays to zero and the synchronous MOSFET is turned off to prevent negative current in the system. In the DEM state, the load current is lower than half of the peak-to-peak inductor current ripple and the switching frequency decreases when the load is further decreased as the device operates in a pulse skipping mode. A switching pulse is set when V_FB drops below 1.2 V.

As the frequency of operation decreases and V_FB remains above 1.2 V (V_REF) with the output capacitor sourcing the load current for greater than 15 µs, the converter enters an ultra-low I_Q sleep mode to prevent draining the input power supply. The input quiescent current (I_Q) required by the LM516x decreases to 10 µA in sleep mode, improving the light-load efficiency of the regulator. In this mode, all internal controller circuits are turned off to ensure very low current consumption by the device. Such low I_Q renders the LM516x as the best option to extend operating lifetime for off-battery applications. The FB comparator and internal bias rail are active to detect when the FB voltage drops below the internal reference V_REF and the converter transitions out of sleep mode into active mode. There is a 9-µs wake-up delay from sleep to active states.