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LTC3649
1
3649f
For more information www.linear.com/LTC3649
Typical applicaTion
FeaTures DescripTion
60V, 4A Synchronous
Step-Down Regulator with
Rail-to-Rail Programmable Output
The LT C
®
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 V
OUT
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 (V
IN
– 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.
Efficiency with V
OUT
= 5V
applicaTions
n
Wide V
IN
Range: 3.1V to 60V
n
Wide V
OUT
Range: 0V to (V
IN
– 0.5V)
n
Single Resistor V
OUT
Programming
n
Integrated 110mΩ Top N-Channel/50mΩ Bottom
N-Channel MOSFETs
n
95% Efficiency with 12V
IN
and 5V
OUT
n
Regulated I
Q
: 440µA, Shutdown I
Q
: 15µA
n
Accurate Current Monitoring (±4%) without Sense
Resistor
n
Accurate Resistor Programmable Frequency
(300kHz to 3MHz) with ±50% Frequency Sync Range
n
Accurate Programmable Output Current
n
Input Voltage Regulation for MPPT Applications
n
±0.8% Output Voltage Accuracy
n
Peak Current Mode Operation
n
Programmable Wire Drop Compensation
n
Burst Mode
®
Operation, Forced Continuous Mode
n
Internal Compensation and Programmable Soft-Start
n
Overtemperature Protection
n
Available in Thermally Enhanced 28-Lead (4mm ×
5mm) QFN and TSSOP Packages
n
Industrial Applications
n
Automotive Applications
L, LT , LT C , LT M , Linear Technology, the Linear logo, Burst Mode and OPTI-LOOP are
registered trademarks and Hot Swap is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents, including
5481178, 5705919, 5847554, 6580258.
V
IN
5.5V TO 60V
22µF
RUN
V
IN
SW
V
OUT
EXTV
CC
MODE/SYNC
SGND
PGND
ITH
V
INREG
INTV
CC
2.2µF
10nF
100k
ISET
10nF
3649 TA01a
47µF
×2
V
OUT
5V
4A
10k
IMON
200k
f
SW
= 500kHz
R
T
LTC3649
BOOST
6.8µH
0.1µF
24V to 5V
OUT
Burst Mode Operation
V
IN
= 12V
V
IN
= 24V
I
OUT
(A)
0
0.5
1
1.5
2
2.5
3
3.5
4
80
82
84
86
88
90
92
94
96
98
100
EFFICIENCY (%)
3649 TA01b
