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Linear Technology Electronic Components Datasheet

LTC3851A Datasheet

Synchronous Step-Down Switching Regulator Controller

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Features
n Wide VIN Range: 4V to 38V Operation
n RSENSE or DCR Current Sensing
n ±1% Output Voltage Accuracy
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 5V Internal Regulator
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, 16-Lead Narrow
SSOP or 3mm × 3mm QFN Package
Applications
n Automotive Systems
n Telecom Systems
n Industrial Equipment
n Distributed DC Power Systems
LTC3851A
Synchronous
Step-Down Switching
Regulator Controller
Description
The LTC®3851A 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 LTC3851A features a precision 0.8V
reference that is compatible with a wide 4V to 38V input
supply range.
The TK/SS pin ramps the output voltage during start‑up.
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 al-
lows the IC to be synchronized to an external clock. The
LTC3851A contains an improved PLL compared to the
LTC3851.
The LTC3851A-1 is a version with a power good output
signal instead of adjustable current limit.
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, Linear Technology and the Linear logo are registered
trademarks and No RSENSE, UltraFast are 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
82.5k
0.1µF
0.1µF
ILIM VIN
FREQ/PLLFLTR TG
RUN SW
LTC3851A
TK/SS BOOST
2200pF
15k
INTVCC
ITH
330pF
BG
GND
SENSE+
MODE/PLLIN
SENSE
VFB
0.1µF
4.7µF
0.68µH
3.01k
22µF
VIN
4.5V TO 36V
VOUT
3.3V
15A
330µF
×2
0.047µF
30.1k
154k
48.7k
3851A TA01a
Efficiency and Power Loss
vs Load Current
100
95
VVIONU=T
12V
= 3.3V
90 EFFICIENCY
85
80
10000
1000
75 POWER LOSS
70
65 100
60
55
50
10
100
1000
10000
LOAD CURRENT (mA)
10
100000
3851A TA01b
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Linear Technology Electronic Components Datasheet

LTC3851A Datasheet

Synchronous Step-Down Switching Regulator Controller

No Preview Available !

LTC3851A
Absolute Maximum Ratings (Note 1)
Input Supply Voltage (VIN).......................... 40V to –0.3V
Topside Driver Voltage (BOOST)................. 46V to –0.3V
Switch Voltage (SW)...................................... 40V to –5V
INTVCC, (BOOST – SW), RUN....................... 6V to –0.3V
STKEN/SSSE,+I,LSIME.N..S...E...........................................................................I.N..T...V6CVC
to
to
0.3V
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)
E-Grade, I-Grade................................. –40°C to 125°C
H-Grade.............................................. –40°C to 150°C
MP-Grade........................................... –55°C to 150°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
GN/MSE............................................................. 300°C
Pin Configuration
TOP VIEW
MODE/PLLIN
FREQ/PLLFLTR
RUN
TK/SS
ITH
FB
SENSE
SENSE+
1
2
3
4
5
6
7
8
16 SW
15 TG
14 BOOST
13 VIN
12 INTVCC
11 BG
10 GND
9 ILIM
GN PACKAGE
16-LEAD PLASTIC SSOP NARROW
TJMAX = 125°C, θJA = 110°C/W
TOP VIEW
MODE/PLLIN 1
16 SW
FREQ/PLLFLTR 2
15 TG
RUN 3
14 BOOST
TK/SS 4
SSEENNSSIFTEEBH–+
5
6
7
8
17
GND
13
12
11
VIBNGINTVCC
10 GND
9 ILIM
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
RUN 1
TK/SS 2
ITH 3
FB 4
16 15 14 13
12
17 11
GND 10
9
5678
BOOST
VIN
INTVCC
BG
UD PACKAGE
16-LEAD (3mm × 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
LTC3851AEGN#PBF
LTC3851AEGN#TRPBF 3851A
16-Lead Plastic SSOP
–40°C to 125°C
LTC3851AIGN#PBF
LTC3851AIGN#TRPBF 3851A
16-Lead Plastic SSOP
–40°C to 125°C
LTC3851AEMSE#PBF
LTC3851AEMSE#TRPBF 3851A
16-Lead Plastic MSOP
–40°C to 125°C
LTC3851AIMSE#PBF
LTC3851AIMSE#TRPBF 3851A
16-Lead Plastic MSOP
–40°C to 125°C
LTC3851AHMSE#PBF
LTC3851AHMSE#TRPBF 3851A
16-Lead Plastic MSOP
–40°C to 150°C
LTC3851AMPMSE#PBF LTC3851AMPMSE#TRPBF 3851A
16-Lead Plastic MSOP
–55°C to 150°C
LTC3851AEUD#PBF
LTC3851AEUD#TRPBF LFPZ
16-Lead (3mm × 3mm) Plastic QFN –40°C to 125°C
LTC3851AIUD#PBF
LTC3851AIUD#TRPBF LFPZ
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/
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Part Number LTC3851A
Description Synchronous Step-Down Switching Regulator Controller
Maker Linear Technology
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LTC3851A Datasheet PDF






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