The LM5002 high-voltage switching regulator features all the functions necessary to implement an efficient boost, flyback, SEPIC or forward current-mode power converter. The operation can be best understood by referring to the block diagram. At the start of each cycle, the oscillator sets the driver logic and turns on the power MOSFET to conduct current through the inductor or transformer. The peak current in the MOSFET is controlled by the voltage at the COMP pin. The COMP voltage increases with larger loads and decrease with smaller loads. This voltage is compared with the sum of a voltage proportional to the power MOSFET current and an internally generated slope compensation ramp. Slope compensation is used in current mode PWM architectures to eliminate subharmonic current oscillation that occurs with static duty cycles greater than 50%. When the summed signal exceeds the COMP voltage, the PWM comparator resets the driver logic, turning off the power MOSFET. The driver logic is then set by the oscillator at the end of the switching cycle to initiate the next power period.

The LM5002 has dedicated protection circuitry to protect the IC from abnormal operating conditions. Cycle-by-cycle current limiting prevents the power MOSFET current from exceeding 0.5A. This feature can also be used to soft start the regulator. Thermal shutdown circuitry holds the driver logic in reset when the die temperature reaches 165°C, and returns to normal operation when the die temperature drops by approximately 20°C. The EN pin can be used as an input voltage undervoltage lockout (UVLO) during start-up to prevent operation with less than the minimum desired input voltage.