ZHCSLQ5D October 2007 – August 2020 LM5067
PRODUCTION DATA
The series pass MOSFET (Q1) is enabled when the input supply voltage (VSYS) is within the operating range defined by the programmable undervoltage lockout (UVLO) and overvoltage lock-out (OVLO) levels. Typically the UVLO level at VSYS is set with a resistor divider (R1-R3) as shown in Figure 9-1. When VSYS is less than the UVLO level, the internal 22 µA current sink at UVLO/EN is enabled, the current source at OVLO is off, and Q1 is held off by the 2.2 mA pull-down current at the GATE pin. VSYS reaches its UVLO level when the voltage at the UVLO/EN pin reaches 2.5V above VEE. Upon reaching the UVLO level, the 22 µA current sink at the UVLO/EN pin is switched off, increasing the voltage at the pin, providing hysteresis for this threshold. With the UVLO/EN pin above 2.5V, Q1 is switched on by the 52 µA current source at the GATE pin.
See Application Information for a procedure to calculate the values of the threshold setting resistors (R1-R3). The minimum possible UVLO level can be set by connecting the UVLO/EN pin to VCC. In this case Q1 is enabled when the operating voltage (VCC – VEE) reaches the POREN threshold (8.4V).