Datasheet

LT3475/LT3475-1
3
3475fb
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: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specifi ed maximum operating junction
temperature may impair device reliability.
Note 3: The LT3475E and LT3475E-1 are guaranteed to meet performance
specifi cations from 0°C to 85°C. Specifi cations over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls. The LT3475I and LT3475I-1
are guaranteed to meet performance specifi cations over the –40°C to
125°C operating temperature range.
Note 4: Current fl ows out of pin.
Note 5: Current fl ows into pin.
Note 6: Current limit is guaranteed by design and/or correlation to static
test. Slope compensation reduces current limit at higher duty cycles.
The ● denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 12V, V
BOOST
= 16V, V
OUT
= 4V unless otherwise noted (Note 3)
PARAMETER CONDITIONS MIN TYP MAX UNITS
LED Pin Current V
ADJ
Tied to V
REF
• 2/3
V
ADJ
Tied to V
REF
• 7/30
LT3475E/LT3475E-1 0°C to 85°C
●
●
0.97
0.94
0.336
0.325
0.31
1.00
0.350
1.03
1.04
0.364
0.375
0.385
A
A
A
A
A
REF Voltage
●
1.22 1.25 1.27 V
Reference Voltage Line Regulation 4V < V
IN
< 40V 0.05 %/V
Reference Voltage Load Regulation 0 < I
REF
< 500μA 0.0002 %/μA
V
ADJ
Pin Bias Current (Note 4)
●
40 400 nA
Switching Frequency R
T
= 24.3k
●
530 600 640 kHz
Maximum Duty Cycle R
T
= 24.3k
R
T
= 4.32k
R
T
= 100k
●
90 95
80
98
%
%
%
Switching Phase R
T
= 24.3k 150 180 210 Deg
Foldback Frequency R
T
= 24.3k, V
OUT
= 0V 80 kHz
SHDN Threshold (to Switch) 2.5 2.6 2.74 V
SHDN Pin Current (Note 5) V
SHDN
= 2.6V 7911 μA
PWM Threshold 0.3 0.8 1.2 V
V
C
Switching Threshold 0.8 V
V
C
Source Current V
C
= 1V 50 μA
V
C
Sink Current V
C
= 1V 50 μA
LED to V
C
Transresistance 500 V/A
LED to V
C
Current Gain 1 mA/μA
V
C
to Switch Current Gain 2.6 A/V
V
C
Clamp Voltage 1.8 V
V
C
Pin Current in PWM Mode V
C
= 1V, V
PWM
= 0.3V
●
10 400 nA
OUT Pin Clamp Voltage (LT3475) 13.5 14 14.5 V
OUT Pin Current in PWM Mode V
OUT
= 4V, V
PWM
= 0.3V
●
25 50 μA
Switch Current Limit (Note 6) 2.3 2.7 3.2 A
Switch V
CESAT
I
SW
=1.5A 350 500 mV
BOOST Pin Current I
SW
=1.5A 25 40 mA
Switch Leakage Current 0.1 10 μA
Minimum Boost Voltage Above SW 1.8 2.5 V
ELECTRICAL CHARACTERISTICS