LT3845A_15 Datasheet, PDF (1/26 Pages) Linear Technology – High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency

FEATURES
n _{High Voltage Operation: Up to 60V}
n _{Synchronizable Up to 600kHz}
n _{Adjustable Constant Frequency: 100kHz to 500kHz}
n _{Output Voltages Up to 36V}
n _{Stable Operation in Current Limit}
n _{Adaptive Nonoverlap Circuitry Prevents Switch}
Shoot-Through
n _{Reverse Inductor Current Inhibit for Discontinuous}
Operation Improves Efficiency with Light Loads
n _{Programmable Soft-Start}
n _{120µA No Load Quiescent Current}
n _{10µA Shutdown Supply Current}
n _{1% Regulation Accuracy}
n _{Standard Gate N-Channel Power MOSFETs}
n _{Reverse Overcurrent Protection}
n _{16-Lead Thermally Enhanced TSSOP Package}
APPLICATIONS
n _{12V and 42V Automotive and Heavy Equipment}
n _{48V Telecom Power Supplies}
n _{Avionics and Industrial Control Systems}
n _{Distributed Power Converters}
LT3845A
High Voltage Synchronous
Current Mode Step-Down
Controller with Adjustable
Operating Frequency
DESCRIPTION
The LT^®3845A is a high voltage, synchronous, current
mode controller used for medium to high power, high
efficiency supplies. It offers a wide 4V to 60V input range
(7.5V minimum start-up voltage). An onboard regulator
simplifies the biasing requirements by providing IC power
directly from V_IN.
Burst Mode^® operation maintains high efficiency at light
loads by reducing IC quiescent current to 120µA. Light load
efficiency is also improved with the reverse inductor current
inhibit function which supports discontinuous operation.
Additional features include adjustable fixed operating
frequency that can be synchronized to an external clock
for noise sensitive applications, gate drivers capable of
driving large N-channel MOSFETs, a precision undervoltage
lockout, 10µA shutdown current, short-circuit protection
and a programmable soft-start.
The LT3845A is available in a 16-lead thermally enhanced
TSSOP package.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners..
Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258.
TYPICAL APPLICATION
High Voltage Step-Down Regulator 48V to 12V at 75W
V_IN
20V
TO 55V
2.2µF
100V
47µF
63V
82.5k
20k
16.2k
1M
V_IN
BOOST
SHDN
TG
1500pF
LT3845A
C_SS
SW
BURST_EN
V_CC
V_FB
BG
V_C
100pF
SYNC
PGND
SENSE⁺
0.1µF
BAS521
Si7370DP
Si7370DP
15µH _0.008Ω
B160
V_OUT
12V
75W
33µF
×3
143k
2200pF
f_SET
49.9k
SENSE^–
SGND
1µF
1N4148
3845A TA01a
Efficiency and Power Loss
vs Load Current
100 _{VIN = 48V}
7
95
6
90
5
85
4
80
3
75
2
LOSS
70
1
65
0.1
1
LOAD CURENT (A)
0
10
3845A TA01b
3845afa
1