Some applications can require a precision enable or custom input voltage lockout (UVLO) functionality. Setting up external UVLO based on the application needs prevents the converter from trying to regulate the output voltage until after the input voltage has reached a desired minimum level. Such function can be used to lower the current demand from the input supply as the supply is still starting up.

The LMZM23600 features a precision enable (EN) input terminal. The EN input logic has two internal thresholds. The first rising threshold is at 0.9V typical. Its purpose is to wake up the internal VCC regulator to bias the internal circuitry. The EN rising threshold to start switching is 1.8V (typical) with 0.5V (typical) hysteresis. A voltage divider from VIN to EN can be used to set the VIN voltage at which the regulator starts the voltage conversion. The EN terminal is rated for up to the input voltage and can be connected directly to VIN for an always-on operation. Pulling the EN pin below 0.4 V puts the LMZM23600 in shutdown mode. In shutdown mode and 12-V input voltage the LMZM23600 only consumes 1.8 µA (typical) of input current.