LM34922 Datasheet, PDF (1/17 Pages) Texas Instruments – 28V, 2A Constant On-Time Switching Regulator with Adjustable Current Limit

LM34922
June 1, 2012
28V, 2A Constant On-Time Switching Regulator with
Adjustable Current Limit
General Description
The LM34922 Constant On-time Step-Down Switching Reg-
ulator features all the functions needed to implement a low
cost, efficient, buck bias regulator capable of supplying up to
2A of load current. This voltage regulator contains an N-
Channel Buck switch, a startup regulator, current limit detec-
tion, and internal ripple control. The constant on-time
regulation principle requires no loop compensation, results in
fast load transient response, and simplifies circuit implemen-
tation. The operating frequency remains constant with line
and load. The adjustable valley current limit detection results
in a smooth transition from constant voltage to constant cur-
rent mode when current limit is reached, without the use of
current limit foldback. The PGD output indicates the output
voltage has increased to within 5% of the expected regulation
value. Additional features include: Low output ripple, VIN un-
der-voltage lock-out, adjustable soft-start timing, thermal
shutdown, gate drive pre-charge, gate drive under-voltage
lock-out, and maximum duty cycle limit.
Features
■ ^{Input operating voltage range: 6V to 28V}
■ ^{Absolute maximum input rating: 30V}
■ ^{Integrated 2A N-Channel Buck Switch}
■ ^{Adjustable current limit allows for smaller inductor}
■ ^{Adjustable output voltage from 2.51V}
■ ^{Minimum ripple voltage at V}_OUT
■ ^{Power Good output}
■ ^{Switching frequency adjustable to 1MHz}
■ ^{COT topology features:}
-Switching frequency remains nearly constant with load
current and input voltage variations
-Ultra-fast transient response
-No loop compensation required
-Stable operation with ceramic output capacitors
-Allows for smaller output capacitor and current sense
resistor
■ ^{Adjustable Soft-Start timing}
■ ^{Thermal shutdown}
■ ^{Precision 2% feedback reference}
Package
■ ^MSOP-10EP
Typical Application, Basic Step-Down Regulator
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