POWER LOSS (W)
LTC3854
Small Footprint, Wide
V Range Synchronous
IN
Step-Down DC/DC Controller
FEATURES DESCRIPTION
n
Wide Operating V Range: 4.5V to 38V The LTC3854 is a high performance synchronous step-
IN
n
R or DCR Current Sensing down switching DC/DC controller that drives an all N-
SENSE
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1% 0.8V Reference Accuracy Over Temperature channel synchronous power MOSFET stage.
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400kHz Switching Frequency
The LTC3854 features a 400kHz constant frequency current
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Dual N-channel MOSFET Synchronous Drive
mode architecture. The LTC3854 operates from a 4.5V to
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Very Low Dropout Operation: 97% Duty Cycle
38V (40V absolute maximum) input voltage range and
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Starts Up Into Pre-Biased Output
regulates the output voltage from 0.8V to 5.5V.
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Adjustable Output Voltage Soft-Start
n The RUN/SS pin provides both soft-start and enable
Output Current Foldback Limiting
features. OPTI-LOOP compensation allows the transient
(Disabled During Soft-Start)
n response to be optimized over a wide range of output ca-
Output Overvoltage Protection
n pacitance and ESR values. Current foldback limits MOSFET
5V LDO for External Gate Drive
n dissipation during short circuit conditions. Current foldback
OPTI-LOOP Compensation Minimizes C
OUT
n functions are disabled during soft-start.
Low Shutdown I : 15A
Q
n
Tiny Thermally Enhanced 12-Pin 2mm 3mm DFN
The LTC3854 has a minimum on-time at 75ns, making it
and MSOP Packages
well suited for high step-down ratios. The strong onboard
MOSFET drivers allow the use of high power external
APPLICATIONS
MOSFETs to produce output currents up to 20A.
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Automotive Systems
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
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Telecom Systems
owners. Protected by U.S. Patents, including 5705919, 6498466, 5408150, 6222231.
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Industrial Equipment
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Distributed DC Power Systems
TYPICAL APPLICATION
High Efficiency Synchronous Step-Down Converter Efficiency and Power Loss
vs Load Current
V 97 2.0
IN
V
IN
6V TO 38V
47F
TG
EFFICIENCY
50V
96 1.6
LTC3854
0.1F 0.1F
RUN/SS BOOST
95 1.2
4.7H
ITH SW
AT 8.2m DCR
V
OUT
2200pF
5V
100pF
94 0.8
10k 7A
0.22F +
INTV
CC
POWER LOSS
5.49k
150F
4.7F
8.06k 93 0.4
FB BG
4.99k
V = 12V
IN
42.2k
SENSE 92 0
1 2 3 4 5 6 7
+
SENSE GND
LOAD CURRENT (A)
3854 TA01b
3854 TA01
3854fb
1
EFFICIENCY (%)LTC3854
(Note 1)
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage (V ) ........................ 40V to 0.3V ITH, FB Voltages ....................................... 2.7V to 0.3V
IN
Top Side Driver Voltage (BOOST) ............... 46V to 0.3V INTV Peak Output Current (Note 8) ....................40mA
CC
Switch Voltage (SW) .................................. 40V to 5.0V Operating Temperature Range
INTV , BOOST-SW .................................... 6V to 0.3V (Notes 2, 3) ..........................................40C to 85C
CC
+
SENSE , SENSE ......................................... 6V to 0.3V Maximum Junction Temperature ...................... 125C
RUN/SS ........................................................ 6V to 0.3V Storage Temperature Range .................. 65C to 125C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
+
1
FB 12 SENSE
+
FB 1 12 SENSE
ITH 2 SENSE
11
ITH 2 11 SENSE
RUN/SS 3 10 V
RUN/SS 3 10 V
IN
IN
13 13
BOOST 4 9 INTV
BOOST 4 9 INTV CC
CC
TG 5 8 BG
TG 8 BG
5
SW 6 7 GND
SW 6 7 GND
MSE PACKAGE
DDB PACKAGE 12-LEAD PLASTIC MSOP
12-LEAD (3mm 2mm) PLASTIC DFN
T = 125C, = 40C/W, = 16C/W
JMAX JA JC
T = 125C, = 76C/W, = 10C/W EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
JMAX JA JC
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3854EDDB#PBF LTC3854EDDB#TRPBF LDPC 40C to 85C
12-Lead (3mm 2mm) Plastic DFN
LTC3854IDDB#PBF LTC3854IDDB#TRPBF LDPC 12-Lead (3mm 2mm) Plastic DFN 40C to 85C
LTC3854EMSE#PBF LTC3854EMSE#TRPBF 3854 12-Lead Plastic MSOP 40C to 85C
LTC3854IMSE#PBF LTC3854IMSE#TRPBF 3854 12-Lead Plastic MSOP 40C to 85C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: