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Linear Technology Electronic Components Datasheet

LTC3851AEMSE-1 Datasheet

Synchronous Step-Down Switching Regulator Controller

No Preview Available !

Features
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
LTC3851A-1
Synchronous
Step-Down Switching
Regulator Controller
Description
The LTC®3851A-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 LTC3851A-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 continu-
ous inductor current mode at light loads and allows the IC
to be synchronized to an external clock. The LTC3851A-1
contains an improved PLL compared to the LTC3851-1.
The LTC3851A-1 is identical to the LTC3851A except that
the ILIM pin is replaced by PGOOD.
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
INTVCC
82.5k
100k
PGO0D
VIN
0.1µF
0.1µF
FREQ/PLLFLTR TG
RUN
SW
LTC3851A-1
TK/SS BOOST
2200pF
15k
INTVCC
ITH
330pF
BG
GND
SENSE+
MODE/PLLIN
SENSE
VFB
0.1µF
4.7µF
0.68µH
3.01k
VIN
22µF 4.5V TO 38V
VOUT
3.3V
15A
330µF
×2
0.047µF 30.1k
154k
48.7k
3851A1 TA01a
Efficiency and Power Loss
vs Load Current
100
VIN = 12V
95 VOUT = 3.3V
90
85
80
75
EFFICIENCY
POWER LOSS
10000
1000
70
65
60
55
50
10
100
10
100
1000 10000 100000
LOAD CURRENT (mA)
3851A1 TA01b
3851a1fa
1


Linear Technology Electronic Components Datasheet

LTC3851AEMSE-1 Datasheet

Synchronous Step-Down Switching Regulator Controller

No Preview Available !

LTC3851A-1
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, 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)
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)
MSE................................................................... 300°C
Pin Configuration
TOP VIEW
MODE/PLLIN 1
16 SW
FREQ/PLLFLTR 2
15 TG
RUN 3
14 BOOST
TK/SS 4
17
13 VIN
ITH 5
GND
12 INTVCC
FB 6
11 BG
SENSE7
10 GND
SENSE+ 8
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
GND
10 INTVCC
FB 4
9 BG
5678
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
LTC3851AEMSE-1#PBF LTC3851AEMSE-1#TRPBF 3851A1
16-Lead Plastic MSOP
–40°C to 125°C
LTC3851AIMSE-1#PBF LTC3851AIMSE-1#TRPBF
3851A1
16-Lead Plastic MSOP
–40°C to 125°C
LTC3851AHMSE-1#PBF LTC3851AHMSE-1#TRPBF 3851A1
16-Lead Plastic MSOP
–40°C to 150°C
LTC3851AMPMSE-1#PBF LTC3851AMPMSE-1#TRPBF 3851A1
16-Lead Plastic MSOP
–55°C to 150°C
LTC3851AEUD-1#PBF
LTC3851AEUD-1#TRPBF
LFQB
16-Lead (3mm × 3mm) Plastic QFN –40°C to 125°C
LTC3851AIUD-1#PBF
LTC3851AIUD-1#TRPBF
LFQB
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/
3851a1fa
2


Part Number LTC3851AEMSE-1
Description Synchronous Step-Down Switching Regulator Controller
Maker Linear Technology
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