SNVSA47C February 2016 – December 2020 LM5165
The precision EN input supports adjustable input undervoltage lockout (UVLO) with hysteresis programmed independently through the HYS pin for application specific power-up and power-down requirements. EN connects to a comparator-based input referenced to a 1.212-V bandgap voltage with 68-mV hysteresis. An external logic signal can be used to drive the EN input to toggle the output on and off and for system sequencing or protection. The simplest way to enable the LM5165's operation is to connect EN directly to VIN. This allows the LM5165 to start up when VIN is within its valid operating range. However, many applications benefit from using a resistor divider RUV1 and RUV2 as shown in Figure 7-5 to establish a precision UVLO level. In tandem with the EN setting, use HYS to increase the voltage hysteresis as needed.
There is also a low IQ shutdown mode when EN is pulled below a base-emitter voltage drop (approximately 0.6 V at room temperature). If EN is below this hard shutdown threshold, the internal LDO regulator powers off and the internal bias supply rail collapses, shutting down the bias currents of the LM5165. The LM5165 operates in standby mode when the EN voltage is between the hard shutdown and precision enable thresholds.