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Linear Technology Electronic Components Datasheet

LTC3851-1 Datasheet

Synchronous Step-Down Switching Regulator Controller

No Preview Available !

FEATURESwww.datasheet4u.com
n Wide VIN Range: 4V to 38V Operation
n RSENSE or DCR Current Sensing
n ±1% Output Voltage Accuracy
n Power Good Output Voltage Monitor
n Phase-Lockable Fixed Frequency: 250kHz to 750kHz
n Dual N-Channel MOSFET Synchronous Drive
n Very Low Dropout Operation: 99% Duty Cycle
n Adjustable Output Voltage Soft-Start or Tracking
n Output Current Foldback Limiting
n Output Overvoltage Protection
n OPTI-LOOP® Compensation Minimizes COUT
n Selectable Continuous, Pulse-Skipping or
Burst Mode® Operation at Light Loads
n Low Shutdown IQ: 20μA
n VOUT Range: 0.8V to 5.5V
n Thermally Enhanced 16-Lead MSOP
or 3mm × 3mm QFN Package
APPLICATIONS
n Automotive Systems
n Telecom Systems
n Industrial Equipment
n Distributed DC Power Systems
LTC3851-1
Synchronous
Step-Down Switching
Regulator Controller
DESCRIPTION
The LTC®3851-1 is a high performance synchronous
step-down switching regulator controller that drives
an all N-channel synchronous power MOSFET stage. A
constant frequency current mode architecture allows a
phase-lockable frequency of up to 750kHz.
OPTI-LOOP compensation allows the transient response
to be optimized over a wide range of output capacitance
and ESR values. The LTC3851-1 features a precision 0.8V
reference and a power good indicator. A wide 4V to 38V (40V
absolute maximum) input supply range encompasses most
battery configurations and intermediate bus voltages.
The TK/SS pin ramps the output voltage during start-up
and shutdown with coincident or ratiometric tracking.
Current foldback limits MOSFET heat dissipation during
short-circuit conditions. The MODE/PLLIN pin selects
among Burst Mode operation, pulse skipping mode or
continuous inductor current mode at light loads and allows
the IC to be synchronized to an external clock.
The LTC3851-1 is identical to the LTC3851 except that the
ILIM pin is replaced by PGOOD.
L, LT, LTC, LTM, Burst Mode 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 5408150, 5481178, 5705919, 5929620, 6304066,
6498466, 6580258, 6611131.
TYPICAL APPLICATION
High Efficiency Synchronous Step-Down Converter
INTVCC
82.5k
100k
PGO0D
VIN
0.1μF
0.1μF
FREQ/PLLFLTR TG
RUN SW
LTC3851-1
TK/SS BOOST
0.1μF
0.68μH
3.01k
22μF
VIN
4.5V TO 38V
VOUT
3.3V
15A
330μF
s2
2200pF
15k
INTVCC
ITH
330pF
BG
GND
SENSE+
PLLIN/MODE
SENSE
VFB
4.7μF
0.047μF 30.1k
154k
48.7k
38511 TA01a
Efficiency and Power Loss
vs Load Current
100
VIN = 12V
95 VOUT = 3.3V
90
EFFICIENCY
10000
85 1000
80
POWER LOSS
75
70
65 100
60
55
50
10
10
100 1000 10000 100000
LOAD CURRENT (mA)
38511TA01b
38511f
1


Linear Technology Electronic Components Datasheet

LTC3851-1 Datasheet

Synchronous Step-Down Switching Regulator Controller

No Preview Available !

LTC3851-1
ABSOLUTE MAXIMUM RATINGS (Note 1)
Input Supply Voltage (VIN) ......................... 40V to –0.3V
Topside Driver Voltage (BOOST) ................ 46V to –0.3V
wwwS.dwatiatschheeVt4oult.caogme (SW) ..................................... 40V to –5V
INTVCC, (BOOST – SW), RUN, PGOOD ........ 6V to –0.3V
TK/SS.................................................... INTVCC to –0.3V
SENSE+, SENSE.......................................... 6V to –0.3V
MODE/PLLIN, FREQ/PLLFLTR............... INTVCC to –0.3V
ITH, VFB Voltages .......................................... 3V to –0.3V
INTVCC Peak Output Current ..................................50mA
Operating Junction Temperature Range
(Notes 2, 3)............................................ –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MSE .................................................................. 300°C
PIN CONFIGURATION
MODE/PLLIN 1
FREQ/PLLFLTR 2
RUN 3
TK/SS 4
ITH 5
FB 6
SENSE7
SENSE+ 8
TOP VIEW
17
16 SW
15 TG
14 BOOST
13 VIN
12 INTVCC
11 BG
10 GND
9 PGOOD
MSE PACKAGE
16-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 35°C/W TO 40°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
TOP VIEW
16 15 14 13
RUN 1
12 BOOST
TK/SS 2 17 11 VIN
ITH 3
10 INTVCC
FB 4
9 BG
5678
UD PACKAGE
16-LEAD (3mm s 3mm) PLASTIC QFN
TJMAX = 125°C, θJA = 68°C/W, θJC = 4.2°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3851EMSE-1#PBF
LTC3851EMSE-1#TRPBF 38511
16-Lead Plastic MSOP
–40°C to 85°C
LTC3851IMSE-1#PBF
LTC3851IMSE-1#TRPBF 38511
16-Lead Plastic MSOP
–40°C to 125°C
LTC3851EUD-1#PBF
LTC3851EUD-1#TRPBF LDNT
16-Lead (3mm × 3mm) Plastic QFN –40°C to 85°C
LTC3851IUD-1#PBF
LTC3851IUD-1#TRPBF LDNT
16-Lead (3mm × 3mm) Plastic QFN –40°C to 125°C
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: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
38511f
2


Part Number LTC3851-1
Description Synchronous Step-Down Switching Regulator Controller
Maker Linear Technology
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