LT3477 Datasheet, PDF (1/20 Pages) Linear Technology – 3A, DC/DC Converter with Dual Rail-to-Rail Current Sense

LT3477
3A, DC/DC Converter
with Dual Rail-to-Rail
Current Sense
FEATURES
DESCRIPTIO
■ _{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
U
APPLICATIO S
The LT^®3477 is a current mode, 3A DC/DC step-up con-
verter 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 I_ADJ1 and I_ADJ2 pins.
Efficiency of up to 91% can be achieved in typical applica-
tions. The LT3477 features a programmable soft-start func-
tion to limit inductor current during start-up. Both inputs
of the error amplifier are available externally allowing posi-
tive and negative output voltages (Boost, Inverting, SEPIC,
Flyback). The switching frequency is programmable from
200kHz to 3.5MHz through an external resistor.
■ _{High Power LED Driver}
■ _{DSL Modems}
■ _{Distributed Power}
■ _{Input/Output Current Limited Boost, SEPIC,}
Inverting, Flyback Converters
■ _{Constant-Voltage, Constant-Current Source}
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 con-
stant-current applications.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
330mA LED Driver with Open LED Protection
10µH
V_IN
5V
3.3µF
I_SP1 I_SN1
SW
200k
3.3µF
V_IN
I_ADJ1
I_ADJ2
FBN
10k
SHDN SHDN LT3477
I_SP2
1k
4.7nF
V_C
I_SN2
V_REF
R_T
FBP GND SS
33nF 22k
0.3Ω
330mA
3477 TA01a
Efficiency
90
85
80
75
70
65
60
55
50
0
0.1
0.2
0.3
0.4
I_OUT (A)
3477 TA01b
3477fb
1