Datasheet

LT3478/LT3478-1
3
34781f
The ● denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. SW = open, V
IN
= V
S
= L = V
OUT
=
⎯
S
⎯
H
⎯
D
⎯
N = 2.7V, LED = open, SS = open,
PWM = CTRL1, CTRL2 = 1.25V, V
REF
= open, V
C
= open, R
T
= 31.6k.
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Frequency: f
OSC
2.25MHz R
T
= 9.09k 2 2.25 2.6 MHz
Line Regulation f
OSC
R
T
= 31.6k, 2.7V < V
IN
< 36V 0.05 0.2 %/V
Nominal R
T
Pin Voltage 0.64 V
Maximum Duty Cycle R
T
= 31.6k
R
T
= 200k
R
T
= 9.09k
●
80 88
97
73
%
%
%
LED Current to V
C
Current Gain (Note 6) 770 µA/A
LED Current to V
C
Voltage Gain (Note 6) 400 V/A
V
C
to Switch Current Gain 13 A/V
V
C
Source Current (Out of Pin) CTRL1 = 0.4V, V
C
= 1V 40 µA
V
C
Sink Current CTRL1 = 0V, V
C
= 1V 40 µA
V
C
Switching Threshold 0.65 V
V
C
High Level (V
OH
) CTRL1 = 0.4V 1.5 V
V
C
Low Level (V
OL
) CTRL1 = 0V 0.2 V
Inductor Current Limit 2.7V < V
S
< 36V
●
4.5 6 6.8 A
Switch Current Limit
●
4.5 6.3 7.5 A
Switch V
CE
SAT I
SW
= 4.5A 270 mV
Switch Leakage Current SW = 42V, V
C
= 0V 1 µA
V
OUT
Overvoltage Protection (OVP)
(Rising)
OVPSET = 1V
OVPSET = 0.3V
41
12.3
V
V
Full Scale LED Current (LT3478-1) CTRL1 = V
REF
, Current Out of LED Pin 1010 1050 1090 mA
700mA LED Current (LT3478-1) CTRL1 = 700mV, Current Out of LED Pin
●
655 700 730 mA
350mA LED Current (LT3478-1) CTRL1 = 350mV, Current Out of LED Pin 325 350 375 mA
100mA LED Current (LT3478-1) CTRL1 = 100mV, Current Out of LED Pin 70 100 130 mA
Full Scale LED Current V
SENSE
(LT3478) CTRL1 = V
REF
, V
SENSE
= V
VOUT
– V
LED
101 105 109 mV
CTRL1 = 700mV, V
SENSE
(LT3478) CTRL1 = 700mV, V
SENSE
= V
VOUT
– V
LED
●
67 70.5 74 mV
CTRL1 = 350mV, V
SENSE
(LT3478) CTRL1 = 350mV, V
SENSE
= V
VOUT
– V
LED
33 35.5 38 mV
CTRL1 = 100mV, V
SENSE
(LT3478) CTRL1 = 100mV, V
SENSE
= V
VOUT
– V
LED
71013 mV
CTRL1, 2 Input Currents CTRL1 = 100mV, CTRL2 = 1.25V or
CTRL2 = 100mV, CTRL1 = 1.25V (Current Out of Pin)
40 nA
OVPSET Input Current OVPSET = 1V, V
OUT
= 41V (Current Out of Pin) 200 nA
PWM Switching Threshold 0.8 1 1.2 V
V
C
Pin Current in PWM Mode V
C
= 1V, PWM = 0 1 50 nA
OUT Pin Current in PWM Mode PWM = 0 1 100 nA
SS Low Level (V
OL
)I
(SS)
= 20µA 0.15 V
SS Reset Threshold V
C
= 0V 0.25 V
SS High Level (V
OH
)V
C
= 0V 1.5 V
Soft-Start (SS) Pin Charge Current SS = 1V, Current Out of Pin, V
C
= 0V 12 µA
Soft-Start (SS) Pin Discharge Current SS = 0.5V, V
C
= 0V 350 µA