LT3844 Datasheet, PDF (1/24 Pages) Linear Technology – High Voltage, Current Mode Switching Regulator Controller with Programmable Operating Frequency

LT3844
High Voltage, Current Mode
Switching Regulator Controller with
Programmable Operating Frequency
FEATURES
DESCRIPTIO
■ _{High Voltage Operation: Up to 60V}
■ _{Output Voltages up to 36V (Step-Down)}
■ _{Programmable Constant Frequency: 100kHz to}
500kHz
■ _{Synchronizable up to 600kHz}
■ _{Burst Mode}^® _{Operation: 120μA Supply Current}
■ _{10μA Shutdown Supply Current}
■ _{±1.3% Reference Accuracy}
■ _{Drives N-Channel MOSFET}
■ _{Programmable Soft-Start}
■ _{Programmable Undervoltage Lockout}
■ _{Internal High Voltage Regulator for Gate Drive}
■ _{Thermal Shutdown}
■ _{Current Limit Unaffected by Duty Cycle}
■ _{16-Pin Thermally Enhanced TSSOP Package}
U
APPLICATIO S
■ _{Industrial Power Distribution}
■ _{12V and 42V Automotive and Heavy Equipment}
■ _{High Voltage Single Board Systems}
■ _{Distributed Power Systems}
■ _Avionics
■ _{Telecom Power}
The LT^®3844 is a DC/DC controller used for medium
power, low part count, high efficiency supplies. It offers
a wide 4V-60V input range (7.5V minimum startup volt-
age) and can implement step-down, step-up, inverting
and SEPIC topologies.
The LT3844 includes Burst Mode operation, which re-
duces quiescent current below 120μA and maintains high
efficiency 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 exter-
nal clock for noise sensitive applications; a gate driver
capable of driving large N-channel MOSFETs; 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.
, 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.
TYPICAL APPLICATIO
High Voltage Step-Down Regulator 48V to 12V, 50W
V_IN
36V
TO
68μF
60V
130k 14.7k
22μF 1 MEG
V_IN
BOOST
SHDN
1000pF
82.5k
C_SS
TG
10Ω
SW
10k
680p
BURST_EN
LT3844
V_FB
V_C
120pF
SYNC
V_CC
1μF
PGND
SENSE⁺
SENSE^–
f_SET
SGND
R7
49.9k
0.22μF
Si7850DP
10μH _0.02Ω
PDS5100H
68μF
V_OUT
12V
50W
33μF
3844 TA01
Efficiency and Power Loss
vs Load Current
90
7
88
6
86
5
EFFICIENCY
84
4
82
3
LOSS
80
2
78
76
0.1
1
1
LOAD CURRENT (A)
V_IN = 48V ₀
10
3844 TA01b
3844fa
1