LT3477
3A, DC/DC Converter
with Dual Rail-to-Rail
Current Sense
DESCRIPTION
FEATURES
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Dual 100mV Rail-to-Rail Current Sense Amplifiers
Wide Input Voltage Range: 2.5V to 25V
3A, 42V Internal Switch
High Efficiency Power Conversion: Up to 93%
Drives LEDs in Boost, Buck-Boost or Buck Mode
Frequency Set by External Resistor: 200kHz to 3.5MHz
Programmable Soft-Start
Low VCESAT Switch: 0.3V at 2.5A
Capable of Positive and Negative Output Voltages
(Boost, Inverting, SEPIC, Flyback)
Available in Thermally Enhanced 20-Lead
(4mm × 4mm) QFN and 20-Lead TSSOP Packages
APPLICATIONS
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The LT®3477 is a current mode, 3A DC/DC step-up converter with dual rail-to-rail current sense amplifiers and an
internal 3A, 42V switch. It combines a traditional voltage
feedback loop and two unique current feedback loops to
operate as a constant-current, constant-voltage source.
Both current sense voltages are set at 100mV and can be
adjusted independently using the IADJ1 and IADJ2 pins. Efficiency of up to 91% can be achieved in typical applications.
The LT3477 features a programmable soft-start function
to limit inductor current during start-up. Both inputs of
the error amplifier are available externally allowing positive and negative output voltages (boost, inverting, SEPIC,
Flyback). The switching frequency is programmable from
200kHz to 3.5MHz through an external resistor.
Available in thermally enhanced 20-pin (4mm × 4mm)
QFN and 20-pin TSSOP packages, the LT3477 provides a
complete solution for both constant-voltage and constantcurrent applications.
High Power LED Driver
DSL Modems
Distributed Power
Input/Output Current Limited Boost, SEPIC,
Inverting, Flyback Converters
Constant-Voltage, Constant-Current Source
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Efficiency
330mA LED Driver With Open LED Protection
10μH
90
3.3μF
ISP1
ISN1
VIN
IADJ1
IADJ2
SHDN
SHDN
3.3μF
200k
SW
80
FBN
10k
LT3477
ISP2
0.3Ω
75
70
65
ISN2
VREF
FBP
GND
60
RT
VC
1k
85
EFFICIENCY (%)
VIN
5V
55
SS
330mA
33nF
22k
50
0
0.1
0.2
0.3
0.4
IOUT (A)
4.7nF
3477 TA01b
3477 TA01a
3477fc
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