LT3475/LT3475-1
5
3475fb
PI FU CTIO S
UUU
Boost Pin Current
Quiescent Current
OUT1, OUT2 (Pins 1, 10): The OUT pin is the input to the
current sense resistor. Connect this pin to the inductor
and the output capacitor.
LED1, LED2 (Pins 2, 9): The LED pin is the output of
the current sense resistor. Connect the anode of the LED
here.
V
IN
(Pins 5, 6): The V
IN
pins supply current to the internal
circuitry and to the internal power switches and must be
locally bypassed.
SW1, SW2 (Pins 4, 7): The SW pin is the output of the
internal power switch. Connect this pin to the inductor,
switching diode and boost capacitor.
BOOST1, BOOST2 (Pins 3, 8): The BOOST pin is used to
provide a drive voltage, higher than the input voltage, to
the internal bipolar NPN power switch.
GND (Pins 15, Exposed Pad Pin 21): Ground. Tie the GND
pin and the exposed pad directly to the ground plane. The
exposed pad metal of the package provides both electrical
contact to ground and good thermal contact to the printed
circuit board. The exposed pad must be soldered to the
circuit board for proper operation. Use a large ground plane
and thermal vias to optimize thermal performance.
Open-Circuit Output Voltage and
Input Current
Reference Voltage
Minimum Input Voltage, Single
1.5A White LED
Minimum Input Voltage, Two Series
Connected 1.5A White LEDs
TYPICAL PERFOR A CE CHARACTERISTICS
UW
SWITCH CURRENT (A)
0
BOOST PIN CURRENT (mA)
20
25
30
1.5
3475 G10
15
10
0.5 1.0 2.0
5
0
35
T
A
= 25°C
V
IN
(V)
0
OUTPUT VOLTAGE (V)
INPUT CURRENT (mA)
25
40
35
40
3475 G12
10
0
10
20
30
50
20
15
30
5
8
12
4
0
14
6
10
2
45
T
A
= 25°C
LT3475-1
LT3475-1
LT3475
LT3475
OUTPUT VOLTAGE
INPUT CURRENT
V
IN
(V)
0
INPUT CURRENT (mA)
4
5
6
30
3475 G11
3
2
10 20 40
1
0
7
T
A
= 25°C
LED CURRENT (A)
0
0
V
IN
(V)
1
2
3
4
6
0.5 1
3475 G14
1.5
5
T
A
= 25°C
TO RUN
LED VOLTAGE
TO START
TEMPERATURE (˚C)
–50
V
REF
(V)
1.26
1.27
1.28
25 75
3475 G13
1.25
1.24
–25 0
50 100 125
1.23
1.22
LED CURRENT (A)
0
5
V
IN
(V)
6
7
8
9
10
0.5 1
3475 G15
1.5
T
A
= 25°C
TO RUN
LED VOLTAGE
TO START
