8.4 Device Functional Modes

8.4.1 Shutdown Mode

EN/UVLO provides ON and OFF control for the LM5012. When VEN/UVLO is below approximately 1.1 V, the

device is in shutdown mode. Both the internal linear regulator and the switching regulator are off. The quiescent

current in shutdown mode drops to 3 µA at VIN = 24 V. The LM5012 also employs internal bias rail undervoltage

protection. If the internal bias supply voltage is below the UV threshold, the regulator remains off.

8.4.2 Standby Mode

The LM5012 enters standby mode during light or no-load on the output. The LM5012 enters standby mode

to prevent draining the input power supply. All internal controller circuits are turned off to reduce the current

consumption. The quiescent current in standby mode is 25 μA (typical).

8.4.3 Active Mode

The LM5012 is in active mode when VEN/UVLO is above the precision enable threshold and the internal bias rail

is above its UV threshold. In COT active mode, the LM5012 is in one of three modes depending on the load

current:

• CCM with fixed switching frequency when load current is above half of the peak-to-peak inductor current

ripple

• Pulse skipping and diode emulation mode (DEM) when the load current is less than half of the peak-to-peak

inductor current ripple in CCM operation

• Current limit CCM with peak current limit protection when an overcurrent condition is applied at the output

8.4.4 Sleep Mode

The LM5012 converter enters DEM during light-load conditions when the inductor current decays to zero. In

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 VFB drops below 1.2 V.

As the frequency of operation decreases and VFB remains above 1.2 V (VREF) with the output capacitor sourcing

the load current for greater than 15 µs, the converter enters an ultra-low IQ sleep mode to prevent draining

the input power supply. The input quiescent current (IQ) required by the LM5012 decreases to 14 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 IQ renders the LM5012 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, VREF, and the converter transitions out of sleep mode

into active mode. There is a 9-µs wake-up delay from sleep to active states.

LM5012

SNVSCA9 – OCTOBER 2022

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