The LM74721-Q1 integrates a boost converter to provide voltage necessary to drive the external N-channel MOSFETs for the ideal diode and the load disconnect stages. The boost converter uses hysteretic mode control scheme for the output voltage (V_CAP-V_VS) regulation along with the constant peak inductor current limit (I_LX). When the CAP–VS voltage is below its nominal value of typically 11.9 V, the low side switch of the boost is turned on and the inductor current rises with the slope of VS/L approximately. After the current hits the limit of 140 mA (typical), then the low side switch is turned off and the inductor current discharges to the output till it reaches zero. The low side switch is turned on again and the switching cycle repeats until the CAP–VS voltage has risen above the boost rising threshold of 13 V (typical). After this threshold level is reached, the boost converter switching is turned OFF to reduce the quiescent current.

For the boost converter to be enabled, the EN pin voltage must be above the specified input high threshold, V_(ENR). The boost converter has a maximum output load capacity of 30-mA typical. If EN pin is pulled low, then the boost converter remains disabled.