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LT3844
1
3844fc
For more information www.linear.com/LT3844
Typical applicaTion
FeaTures
applicaTions
DescripTion
High Voltage, Current Mode
Switching Regulator Controller with
Programmable Operating Frequency
n
Industrial Power Distribution
n
12V and 42V Automotive and Heavy Equipment
n
High Voltage Single Board Systems
n
Distributed Power Systems
n
Avionics
n
Telecom Power
High Voltage Step-Down Regulator 48V to 12V, 50W
Efficiency and Power Loss
vs Load Current
n
High Voltage Operation: Up to 60V
n
Output Voltages Up to 36V (Step Down)
n
Programmable Constant Frequency: 100kHz to
500kHz
n
Synchronizable up to 600kHz
n
Burst Mode
®
Operation: 120µA Supply Current
n
10µA Shutdown Supply Current
n
±1.3% Reference Accuracy
n
Drives N-Channel MOSFET
n
Programmable Soft-Start
n
Programmable Undervoltage Lockout
n
Internal High Voltage Regulator for Gate Drive
n
Thermal Shutdown
n
Current Limit Unaffected by Duty Cycle
n
16-Pin Thermally Enhanced TSSOP Package
The LT
®
3844 is a DC/DC controller used for medium power,
low part count, high efficiency supplies. It offers a wide
4V to 60V input range (7.5V minimum start-up voltage)
and can implement step-down, step-up, inverting and
SEPIC topologies.
The LT3844 includes Burst Mode operation, which reduces
quiescent current below 120µA and maintains high effi
-
ciency at light loads. An internal high voltage bias regulator
allows for simple biasing.
Additional features include current mode control for fast
line and load transient response;
programmable fixed
operating frequency that can be synchronized to an ex
-
ternal clock for noise sensitive applications; a gate driver
capable of driving large N-channel MOSFET
s
; a precision
undervoltage lockout function; 10µA shutdown current;
short-circuit protection and a programmable soft-start
function.
The LT3844 is available in a 16-lead thermally enhanced
TSSOP package.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5731694, 6498466, 6611131
V
IN
SHDN
C
SS
BURST_EN
V
FB
V
C
SYNC
f
SET
BOOST
TG
SW
V
CC
PGND
SENSE
+
SENSE
–
SGND
LT3844
3844 TA01
R7
49.9k
V
OUT
12V
50W
68µF
680p
22µF
120pF
68µF
10k
10Ω
1000pF
0.22µF
10µH
33µF
0.015Ω
14.7k
130k
82.5k
1M
1µF
PDS5100H
Si7850DP
V
IN
36V TO 60V
LOAD CURRENT (A)
76
82
80
78
90
88
86
84
0
3
2
1
7
6
5
4
3844 TA01b
EFFICIENCY (%)
POWER LOSS (W)
0.1
10
1
LOSS
EFFICIENCY
V
IN
= 48V
