LT3477_15 Datasheet, PDF (1/20 Pages) Linear Technology – 3A, DC/DC Converter with Dual Rail-to-Rail Current Sense

FEATURES
n _{Dual 100mV Rail-to-Rail Current Sense Amplifiers}
n _{Wide Input Voltage Range: 2.5V to 25V}
n _{3A, 42V Internal Switch}
n _{High Efficiency Power Conversion: Up to 93%}
n _{Drives LEDs in Boost, Buck-Boost or Buck Mode}
n _{Frequency Set by External Resistor: 200kHz to 3.5MHz}
n _{Programmable Soft-Start}
n _{Low VCESAT Switch: 0.3V at 2.5A}
n _{Capable of Positive and Negative Output Voltages}
(Boost, Inverting, SEPIC, Flyback)
n _{Available in Thermally Enhanced 20-Lead}
(4mm × 4mm) QFN and 20-Lead TSSOP Packages
APPLICATIONS
n _{High Power LED Driver}
n _{DSL Modems}
n _{Distributed Power}
n _{Input/Output Current Limited Boost, SEPIC,}
Inverting, Flyback Converters
n _{Constant-Voltage, Constant-Current Source}
LT3477
3A, DC/DC Converter
with Dual Rail-to-Rail
Current Sense
DESCRIPTION
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. Ef-
ficiency 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 posi-
tive 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 constant-
current applications.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
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
V_REF
FBP
GND
I_SN2
R_T
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
3477fc
1