SNVSBN6 April 2020 LM5181-Q1
The precision EN/UVLO input supports adjustable input undervoltage lockout (UVLO) with hysteresis for application specific power-up and power-down requirements. EN/UVLO connects to a comparator with a 1.5-V reference voltage and 50-mV hysteresis. An external logic signal can be used to drive the EN/UVLO input to toggle the output on and off for system sequencing or protection. The simplest way to enable the LM5181-Q1 is to connect EN/UVLO directly to VIN. This allows the LM5181-Q1 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 19 to establish a precision UVLO level.
The LM5181-Q1 also provides a low-IQ shutdown mode when the EN/UVLO voltage is pulled below a base-emitter voltage drop (approximately 0.6 V at room temperature). If the EN/UVLO voltage 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 LM5181-Q1. The LM5181-Q1 operates in standby mode when the EN/UVLO voltage is between the hard shutdown and precision-enable thresholds.