The LM5009 Step Down Switching Regulator features all of the functions needed to implement a low cost, efficient, Buck bias regulator. This device is capable of driving a 150 mA load current from a 9.5V to 95V input source. The switching frequency can exceed 600 kHz, depending on the input and output voltages. The output voltage may be set from 2.5V to 85V. This high voltage regulator contains an N-Channel buck switch and internal startup regulator. The device is easy to implement and is provided in the MSOP-8 and the thermally enhanced LLP-8 packages. The LM5009 is a well suited alternative to a high voltage monolithic or discrete linear solution where the power loss becomes unacceptable. The regulator's operation is based on a hysteretic control scheme using an ON time inversely proportional to VIN. This feature allows the operating frequency to remain relatively constant over load and input voltage variations. The hysteretic control requires no loop compensation, resulting in an ultra-fast transient response. An intelligent current limit is implemented with forced OFF time, which is inversely proportional to Vout. This scheme ensures short circuit protection while providing minimum foldback. Other features include: Thermal Shutdown, Vcc under-voltage lockout, Gate drive under-voltage lockout, and Maximum Duty Cycle limiter.