The LM25018 device contains an internal high voltage linear regulator with a nominal output of 7.6 V. The input pin (V_IN) can be connected directly to the line voltages up to 48 V. The V_CC regulator is internally current limited to 30 mA. The regulator sources current into the external capacitor at V_CC. This regulator supplies current to internal circuit blocks including the synchronous MOSFET driver and the logic circuits. When the voltage on the V_CC pin reaches the undervoltage lockout threshold of 4.5 V, the IC is enabled.

The V_CC regulator contains an internal diode connection to the BST pin to replenish the charge in the gate drive boot capacitor when SW pin is low.

At high input voltages, the power dissipated in the high voltage regulator is significant and can limit the overall achievable output power. As an example, with the input at 48 V and switching at high frequency, the V_CC regulator can supply up to 7 mA of current, resulting in 48 V × 7 mA = 336 mW of power dissipation. If the V_CC voltage is driven externally by an alternate voltage source, between 8.55 V and 13 V, the internal regulator is disabled. This reduces the power dissipation in the IC.