LM25011/LM25011Q
LM25011A/LM25011AQ
January 27, 2011
42V, 2A Constant On-Time Switching Regulator with
Adjustable Current Limit
General Description
The LM25011 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 high 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.
The LM25011A has a shorter minimum off-time than the
LM25011, which allows for higher frequency operation at low
input voltages.
Features
■ LM25011Q is an Automotive Grade product that is AEC-
Q100 grade 1 qualified (-40°C to +125°C operating
junction temperature)
■ LM25011A allows low dropout operation at high switching
frequency
■ Input operating voltage range: 6V to 42V
■ Absolute maximum input rating: 45V
■ 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 2 MHz
■ 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
30094601
2011 National Semiconductor Corporation
300946
www.national.com
LM25011/LM25011Q
/
LM25011A/LM25011AQ
42V,
2A
Constant
On-Time
Switching
Regulator
with
Adjustable
Current
Limit