LT3478/LT3478-1
4
34781f
JUNCTION TEMPERATURE (°C)
–50
CURRENT LIMIT (A)
7.0
6.5
6.0
5.5
5.0
4.5
–25 0 25
3478 G06
50 75 100 125
INDUCTOR
SWITCH
SWITCH CURRENT (A)
0.0
SWITCH V
CE
(SAT) (mV)
240
210
180
120
60
0
1.0 2.0 2.5 4.5
3478 G05
0.5 1.5 3.0 3.5 4.0
T
A
= 25°C
JUNCTION TEMPERATURE (°C)
–50
CTRL1 PIN CURRENT X (–1) (nA)
50
40
30
20
10
0
–25 0 25
3478 G04
50 75 100 125
CTRL1 = 0.9V
CTRL1 = 0.7V
CTRL1 = 0.35V
CTRL1 = 0.1V
CTRL2 = V
REF
CTRL1 AND CTRL2 PINS
INTERCHANGEABLE
CTRL1 (V)
0
LED CURRENT (mA)
1.40
3478 G01
0.35 0.70 1.05
1400
1050
700
350
0
T
A
= 25°C
CTRL2 = V
REF
(FOR LT3478 SCALE BY 0.1Ω/R
SENSE
)
LT3478-1
V
REF
JUNCTION TEMPERATURE (°C)
–50
LED CURRENT (mA)
1400
1050
700
350
0
–25 0 25
3478 G02
50 75 100 125
I
LED
= 1050mA, CTRL1 = CTRL2 = V
REF
I
LED
= 100mA, CTRL1 = 100mV,
CTRL2 = V
REF
(FOR LT3478 SCALE BY 0.1Ω/R
SENSE
)
LT3478-1
LED Current vs CTRL1 LED Current vs Temperature
LED Current vs PWM Duty Cycle
Wide PWM Dimming Range
(3000:1)
CTRL1 Pin Current vs
Temperature
Switch V
CE
(SAT) vs Switch
Current
Switch and Inductor Peak Current
Limits vs Temperature
TYPICAL PERFOR A CE CHARACTERISTICS
UW
PWM DUTY CYCLE (%)
1000
100
10
1
0
0.01 1 10 100
3478 G03
0.1
LED CURRENT (mA)
T
A
= 25°C
V
IN
= V
S
= 12V
6 LEDS AT 500mA
PWM FREQ = 100Hz
CTRL1 = 0.5V
CTRL2 = V
REF
F
OSC
= 1.6MHz
L = 2.2µH
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT3478EFE/LT3478EFE-1 are guaranteed to meet performance
specifi cations from 0°C to 125°C junction temperature. Specifi cations over
the –40°C to 125°C operating junction temperature range are assured by
design, characterization and correlation with statistical process controls.
The LT3478IFE/LT3478IFE-1 are guaranteed over the full –40°C to 125°C
operating junction temperature range.
Note 3: This IC includes over-temperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when over-temperature protection is active.
Continuous operation above the specifi ed maximum operating junction
temperature may impair device reliability.
Note 4: For maximum operating ambient temperature, see the “Thermal
Calculations” section in the Applications Information section.
Note 5: The maximum operational voltage for V
IN
is limited by thermal and
effi ciency considerations. Power switch base current is delivered from V
IN
and should therefore be driven from the lowest available power supply in
the system. See “Thermal Calculations” in the Applications Information
section.
Note 6: For LT3478, parameter scales • (R
SENSE
/0.1Ω).
ELECTRICAL CHARACTERISTICS
