LTC3854_15 Datasheet, PDF (1/28 Pages) Linear Technology – Small Footprint, Wide VIN Range Synchronous Step-Down DC/DC Controller

LTC3854
Small Footprint, Wide
V_IN Range Synchronous
Step-Down DC/DC Controller
FEATURES
DESCRIPTION
n _{Wide Operating VIN Range: 4.5V to 38V}
n _{RSENSE or DCR Current Sensing}
n _{±1% 0.8V Reference Accuracy Over Temperature}
n _{400kHz Switching Frequency}
n _{Dual N-channel MOSFET Synchronous Drive}
n _{Very Low Dropout Operation: 97% Duty Cycle}
n _{Starts Up Into Pre-Biased Output}
n _{Adjustable Output Voltage Soft-Start}
n _{Output Current Foldback Limiting}
(Disabled During Soft-Start)
n _{Output Overvoltage Protection}
n _{5V LDO for External Gate Drive}
n _OPTI-LOOP^® _{Compensation Minimizes COUT}
n _{Low Shutdown IQ: 15µA}
n _{Tiny Thermally Enhanced 12-Pin 2mm × 3mm DFN}
and MSOP Packages
APPLICATIONS
n _{Automotive Systems}
n _{Telecom Systems}
n _{Industrial Equipment}
n _{Distributed DC Power Systems}
The LTC3854^® is a high performance synchronous step-
down switching DC/DC controller that drives an all N-
channel synchronous power MOSFET stage.
The LTC3854 features a 400kHz constant frequency current
mode architecture. The LTC3854 operates from a 4.5V to
38V (40V absolute maximum) input voltage range and
regulates the output voltage from 0.8V to 5.5V.
The RUN/SS pin provides both soft-start and enable
features. OPTI-LOOP compensation allows the transient
response to be optimized over a wide range of output ca-
pacitance and ESR values. Current foldback limits MOSFET
dissipation during short circuit conditions. Current foldback
functions are disabled during soft-start.
The LTC3854 has a minimum on-time at 75ns, making it
well suited for high step-down ratios. The strong onboard
MOSFET drivers allow the use of high power external
MOSFETs to produce output currents up to 20A.
L, LT, LTC, LTM, Linear Technology, the Linear logo and OPTI-LOOP are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners. Protected by U.S. Patents, including 5705919, 6498466, 5408150, 6222231.
TYPICAL APPLICATION
High Efficiency Synchronous Step-Down Converter
0.1µF
2200pF
10k
8.06k
42.2k
V_IN
TG
LTC3854
RUN/SS BOOST
ITH
SW
100pF
INTV_CC
FB
BG
SENSE^–
SENSE⁺ GND
0.1µF
4.7µF
47µF
V_IN
6V TO 38V
50V
4.7µH
AT 8.2mΩ DCR
0.22µF
5.49k
4.99k
V_OUT
5V
+ ^7A
150µF
3854 TA01
Efficiency and Power Loss
vs Load Current
97
2.0
EFFICIENCY
96
1.6
95
1.2
94
0.8
POWER LOSS
93
0.4
92
1
V_IN = 12V ₀
2
3
4
5
6
7
LOAD CURRENT (A)
3854 TA01b
3854fb
1