LTC3649
60V, 4A Synchronous
Step-Down Regulator with
Rail-to-Rail Programmable Output
FEATURES
DESCRIPTION
nn Wide VIN Range: 3.1V to 60V
nn Wide VOUT Range: 0V to (VIN – 0.5V)
nn Single Resistor VOUT Programming
nn Integrated 110mΩ Top N-Channel/50mΩ Bottom
N-Channel MOSFETs
nn 95% Efficiency with 12VIN and 5VOUT
nn Regulated IQ: 440µA, Shutdown IQ: 18µA
nn Accurate Current Monitoring (±4%) without Sense
Resistor
nn Accurate Resistor Programmable Frequency
(300kHz to 3MHz) with ±50% Frequency Sync Range
nn Accurate Programmable Output Current
nn Input Voltage Regulation for MPPT Applications
nn ±0.8% Output Voltage Accuracy
nn Peak Current Mode Operation
nn Programmable Wire Drop Compensation
nn Burst Mode® Operation, Forced Continuous Mode
nn Internal Compensation and Programmable Soft-Start
nn Overtemperature Protection
nn Available in Thermally Enhanced 28-Lead (4mm ×
5mm) QFN and TSSOP Packages
The LTC®3649 is a high efficiency 60V, 4A synchronous
monolithic step-down regulator. The regulator features
a single resistor programmable output voltage, internal
compensation and high efficiencies over a wide VOUT range.
The step-down regulator operates from an input voltage
range of 3.1V to 60V and provides an adjustable rail-to-rail
output range from (VIN – 0.5V) to ground while delivering
up to 4A of output current. The switching frequency is
also adjusted with an external resistor. A user-selectable
mode input is provided to allow the user to trade off ripple
noise for efficiency at light loads; Burst Mode operation
provides the highest efficiency at light loads, while forced
continuous mode provides low output ripple. The MODE/
SYNC pin can also be used to allow the user to synchronize
the switching frequency to an external clock.
The LTC3649 operates with a peak current mode architec-
ture that allows for fast transient response with inherent
cycle-to-cycle current limit protection. It also features
programmable output current limit, current monitoring
and input voltage regulation.
APPLICATIONS
L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and OPTI-LOOP are
registered trademarks of Analog Devices, Inc. All other trademarks are the property of their
respective owners. Protected by U.S. Patents, including 5481178, 5705919, 5847554, 6580258.
nn Industrial Applications
nn Automotive Applications
TYPICAL APPLICATION
24V to 5VOUT Burst Mode Operation
0.1µF
VIN
5.5V TO 60V
VIN
RUN
22µF
ITH
VINREG
INTVCC
2.2µF ISET
BOOST SW
VOUT
LTC3649
EXTVCC
MODE/SYNC
SGND
PGND
RT IMON
6.8µH
100k
10nF 200k 10k
10nF
fSW = 500kHz
47µF
×2
VOUT
5V
4A
3649 TA01a
100
98
96
94
92
90
88
86
84
82
80
0
Efficiency with VOUT = 5V
VIN = 12V
VIN = 24V
0.5 1 1.5 2 2.5 3 3.5 4
IOUT (A)
3649 TA01b
For more information www.linear.com/LTC3649
3649fb
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