LT3740
Wide Operating Range,
Valley Mode, No R
SENSE
Synchronous Step-Down Controller
FEATURES DESCRIPTION
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Wide V Range: 2.2V to 22V
The LT 3740 is a synchronous step-down switching
IN
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Internal Boost Provides 6V Gate Drive
regulator controller that drives N-channel power MOSFET
For V Down to 2.2V
stages. The controller uses valley current mode architecture
IN
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No Sensing Resistor Required
to achieve very low duty cycles with excellent transient
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Dual N-Channel MOSFET Synchronous Drive
response without requiring a sense resistor.
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Valley Current Mode Control
The LT3740 includes an internal step-up converter to
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Optimized for High Step-Down Ratio
provide a bias 7.8V higher than the input voltage for the
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Power Good Output Voltage Monitor
drive. This enables the part to work from an input voltage
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0.8V Reference
as low as 2.2V.
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Three Pin-Selected Current Limit Levels
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The XREF pin is an external reference input that allows the
Constant Switching Frequency: 300kHz
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user to override the internal 0.8V feedback reference with
Programmable Soft-Start
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any lower value, allowing full control of the output voltage
Output Voltage Tracking
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during operation, output voltage tracking or soft-start.
Available in 16-Pin 5mm 3mm DFN
The LT3740 has three current limit levels that can be
chosen by connecting the RANGE pin to ground, open,
APPLICATIONS
and input respectively.
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Notebook and Palmtop Computers, PDA
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
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No R is a trademark of Linear Technology Corporation. All other trademarks are the
Portable Instruments SENSE
property of their respective owners.
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Distributed Power Systems
TYPICAL APPLICATION
High Ef ciency Step-Down Converter Ef ciency vs Load Current
V
IN
94
3V to 12V
1F
22H
LT3740
92
10F
SWB BGDP
V = 5V
IN
V = 3V
IN
BIAS
V 90
IN
1
M1
TGATE
HAT2168H
SHDN 88
0.9H
V
1 OUT
SW 1.8V
15k
86 V = 12V
10A IN
+
XREF
SN
D1
100F
84
1 B320A
M2
s 3
BGATE HAT2165H
0.22F
82
39pF
V = 1.8V
OUT
15k SN
80
105k
V
C
0 2 46 8 10
PGND
20k
LOAD CURRENT (A)
RANGE GND FB
3740 TA01b
1nF
80.6k
22pF
3740 TA01a
3740fc
1
EFFICIENCY (%)LT3740
ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION
(Note 1)
TOP VIEW
SN , BGATE, V , FB, XREF, PGOOD Voltages .............10V
C
SN 1 16 V
C
V ,SHDN, SW, Range Voltages ...............................22V
IN
+
PGND 2 15 FB
BIAS, TGATE, BGDP, SN Voltages ............................32V
BGATE 3 14 XREF
SWB Voltage ............................................................36V
BGDP 4 13 SHDN
Maximum Junction Temperature........................... 125C
17
+
SN 5 12 PGOOD
Operating Temperature Range (Note 2)....40C to 85C
SW 6 11 RANGE
Storage Temperature Range ...................65C to 125C
TGATE 7 10 V
IN
BIAS 8 9 SWB
DHC PACKAGE
16-LEAD (5mm 3mm) PLASTIC DFN
T = 125C, = 43C/W
JMAX JA
EXPOSED PAD IS GND (PIN 17), MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3740EDHC#PBF LT3740EDHC#TRPBF 3740 40C to 85C
16-Lead (5mm 3mm) Plastic DFN
LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3740EDHC LT3740EDHC#TR 3740 16-Lead (5mm 3mm) Plastic DFN 40C to 85C
Consult LTC Marketing for parts speci ed with wider operating temperature ranges.
For more information on lead free part marking, go to: