SNVSB29C October 2018 – June 2021 LM5143-Q1
The LM5143-Q1 operates with peak current-mode control such that the compensation voltage is proportional to the peak inductor current. During no-load or light-load conditions, the output capacitor discharges very slowly. As a result, the compensation voltage does not demand driver output pulses on a cycle-by-cycle basis. When the LM5143-Q1 controller detects 16 missed switching cycles, it enters standby mode and switches to a low IQ state to reduce the current drawn from the input. For the LM5143-Q1 to go into standby mode, the controller must be programmed for diode emulation (VDEMB < 0.4 V).
There are two standby modes: ultra-low IQ and normal mode. To enter ultra-low IQ mode, connect MODE to AGND through a 10-kΩ resistor. In ultra-low IQ mode, the transconductance amplifier gain is reduced from 1200 µS to 60 µS. The typical ultra-low IQ is 15 μA with channel 1 set to 3.3 V and the channel 2 disabled. If ultra-low IQ is not required, connect MODE to AGND. In normal mode, the IQ is 25 μA with channel 1 set to 3.3 V and the second channel disabled.