LT3478 Просмотр технического описания (PDF) - Linear Technology
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LT3478 Datasheet PDF : 24 Pages
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LT3478/LT3478-1
ELECTRICAL CHARACTERISTICS
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
specifications from 0°C to 125°C junction temperature. Specifications 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 specified 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 VIN is limited by thermal and
efficiency considerations. Power switch base current is delivered from VIN
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 • (RSENSE/0.1Ω).
TYPICAL PERFOR A CE CHARACTERISTICS
LED Current vs CTRL1
1400
TA = 25°C
CTRL2 = VREF
(FOR LT3478 SCALE BY 0.1Ω/RSENSE)
1050
LT3478-1
700
LED Current vs Temperature
1400 (FOR LT3478 SCALE BY 0.1Ω/RSENSE)
1050
ILED = 1050mA, CTRL1 = CTRL2 = VREF
LT3478-1
700
LED Current vs PWM Duty Cycle
Wide PWM Dimming Range
(3000:1)
1000
100
10
TA = 25°C
VIN = VS = 12V
6 LEDS AT 500mA
PWM FREQ = 100Hz
CTRL1 = 0.5V
CTRL2 = VREF
FOSC = 1.6MHz
L = 2.2µH
350
0
0
VREF
0.35
0.70
1.05
1.40
CTRL1 (V)
3478 G01
350
ILED = 100mA, CTRL1 = 100mV,
CTRL2 = VREF
0
–50 –25 0 25 50 75 100 125
JUNCTION TEMPERATURE (°C)
3478 G02
1
0
0.01
0.1
1
10
PWM DUTY CYCLE (%)
100
3478 G03
CTRL1 Pin Current vs
Temperature
50
40
CTRL1 = 0.1V
30
20 CTRL2 = VREF
CTRL1 AND CTRL2 PINS
INTERCHANGEABLE
10
CTRL1 = 0.35V
CTRL1 = 0.7V
0
–50 –25 0
CTRL1 = 0.9V
25 50 75 100 125
JUNCTION TEMPERATURE (°C)
3478 G04
4
Switch VCE (SAT) vs Switch
Current
240 TA = 25°C
210
180
120
60
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
SWITCH CURRENT (A)
3478 G05
Switch and Inductor Peak Current
Limits vs Temperature
7.0
6.5
SWITCH
6.0
INDUCTOR
5.5
5.0
4.5
–50 –25 0 25 50 75 100 125
JUNCTION TEMPERATURE (°C)
3478 G06
34781f
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