ZHCSL48 April 2020 LM5181-Q1
PRODUCTION DATA.
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.
Figure 19. Programmable Input Voltage UVLO With Hysteresis Use Equation 10 and Equation 11 to calculate the input UVLO voltages turnon and turnoff voltages, respectively.
where
where
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.