1FEATURES

2? Functional Input Voltage Range: 8V to 33V

? DSBGA package

? Input Over-Voltage Shutdown at ?35V

? Transient Capability to 50V

? Integrated N-Channel buck switch

? Valley current limit varies with VIN and VOUT to

reduce excessive inductor current

? On-time is reduced when in current limit

? Integrated start-up regulator

? No loop compensation required

? Ultra-Fast transient response

? Maximum switching frequency: 2 MHz

? Operating frequency remains nearly constant

with load current and input voltage variations

? Programmable soft-start

? Precision internal reference

? Adjustable output voltage

? Thermal shutdown

TYPICAL APPLICATIONS

? High Efficiency Point-Of-Load (POL) Regulator

? Non-Isolated Buck Regulator

? Secondary High Voltage Post Regulator

PACKAGE

? 12-Bump DSBGA Package

DESCRIPTION

The LM34917A Step-Down Switching Regulator features all the functions needed to implement a low

cost, efficient, buck bias regulator capable of

supplying at least 1.25A to the load. To reduce

excessive switch current due to the possibility of a

saturating inductor the valley current limit threshold

changes with input and output voltages, and the on-

time is reduced when current limit is detected. This

buck regulator contains an N-Channel Buck Switch,

and is available in the 12 pin DSBGA package. The constant on-time feedback regulation scheme

requires no loop compensation, results in fast load

transient response, and simplifies circuit

implementation. The operating frequency remains

constant with line and load variations due to the inverse relationship between the input voltage and

the on-time. The valley current limit results in a

smooth transition from constant voltage to constant

current mode when current limit is detected, reducing

the frequency and output voltage, without the use of

foldback. Additional features include: VCC under- voltage lock-out, input over-voltage shutdown,

thermal shutdown, gate drive under-voltage lock-out,

and maximum duty cycle limit.