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.