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LM25085A
PGATE
ISEN
GND
VCC
ADJ
4.5V to 42V
Input
V
IN
GND
SHUTDOWN
C
IN
R
T
C
VCC
C
ADJ
R
ADJ
Q1
D1
L1
Cff
C
OUT
R
FB2
R
FB1
V
OUT
GND
VIN
RT
LM25085A
www.ti.com
SNVS601B –JANUARY 2009–REVISED MARCH 2013
LM25085A 42V Constant On-Time PFET Buck Switching Controller with 0.9V Reference
Check for Samples: LM25085A
1
FEATURES
DESCRIPTION
The LM25085A is a functional variant of the LM25085
2
• Wide 4.5V to 42V Input Voltage Range
COT PFET Buck Switching Controller. The functional
• Adjustable Current Limit using R
DS(ON)
or a
differences of the LM25085A are: The feedback
Current Sense Resistor
reference voltage is 0.9V, the forced off-time after
• Programmable Switching Frequency to 1MHz
current limit detection is longer, and the soft-start time
is shorter (1.8 ms).
• No Loop Compensation Required
The LM25085A is a high efficiency PFET switching
• Ultra-Fast Transient Response
regulator controller that can be used to quickly and
• Nearly Constant Operating Frequency with
easily develop a small, efficient buck regulator for a
Line and Load Variations
wide range of applications. This high voltage
• Adjustable Output Voltage from 0.9V
controller contains a PFET gate driver and a high
voltage bias regulator which operates over a wide
• Precision ±2% Feedback Reference
4.5V to 42V input range. The constant on-time
• Capable of 100% Duty Cycle Operation
regulation principle requires no loop compensation,
• Internal Soft-Start Timer
simplifies circuit implementation, and results in ultra-
• Integrated High Voltage Bias Regulator
fast load transient response. The operating frequency
remains nearly constant with line and load variations
• Thermal Shutdown
due to the inverse relationship between the input
voltage and the on-time. The PFET architecture
PACKAGE
allows 100% duty cycle operation for a low dropout
• HVSSOP-PowerPAD-8
voltage. Either the R
DS(ON)
of the PFET or an external
sense resistor can be used to sense current for over-
• VSSOP-8
current detection.
• WSON-8 (3 mm x 3 mm)
Typical Application, Basic Step Down Controller
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Copyright © 2009–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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