LT3797
28
3797fa
For more information www.linear.com/LT3797
Typical applicaTions
Triple Boost LED Driver
Efficiency and Output Current vs V
IN
Fault (Short LED) Protection without R
SS1-3
: Hiccup Mode Fault (Short LED) Protection with R
SS1-3
: Latchoff Mode
500:1 PWM Dimming at 120Hz
V
IN
(V)
0
50
EFFICIENCY (%)
OUTPUT CURRENT (A)
55
65
70
75
100
85
10
20
25
3797 TA02b
60
90
95
80
0
0.2
0.6
0.8
1.0
2.0
1.4
0.4
1.6
1.8
1.2
5 15
30
35
40
PWM1-3 = 2V
EFFICIENCY
OUTPUT CURRENT
PWM
5V/DIV
I
L
5A/DIV
I
LED
1A/DIV
5µs/DIVV
IN
= 12V
3797 TA02c
SS1-3
2V/DIV
I
M2,4,6
10A/DIV
V
LED1-3
+
50V/DIV
F LT 1-3
10V/DIV
50ms/DIV
3797 TA02d
SS1-3
2V/DIV
I
M2,4,6
10A/DIV
V
LED1-3
+
100V/DIV
F LT 1-3
10V/DIV
50ms/DIV
3797 TA02e
R
SS1-3
**
470k
OVLO CTRL1-3V
REF
V
REF
RT SYNC SW1 BOOST INTV
CC
INTV
CC
GND VC1-3
FBH1-3
SW2
R
T
47.5k
310kHz
C
SS1-3
0.1µF
L
PWR
47µH
PWM1-3
F LT 1-3
F LT 1-3
SS1-3
SS1-3
INTV
CC
V
REF
100k
C
IN1-3
4.7µF
×3
C
IN3
1µF
C
BST
0.1µF
*D4-6: OPTIONAL FOR SHORT LED PROTECTION
**R
SS1-3
: OPTIONAL FOR FAULT LATCHOFF
C
VCC
10µF
3797 TA02
C
C1-3
6.8nF
R
C1-3
3.9k
R12-R14
1M
R9-R11
23.2k
R7
100k
V
IN
2.5V TO 40V
(60V TRANSIENT,
41V INTERNAL
OVLO PROTECTION)
R8
105k
ISP1-3
EN/UVLO
D1-D3: DIODES INC. PDS360
D4-D6: VISHAY SILICONIX ES1B
L1-L3: COILTRONICS HC9-100-R
L
PWR
: COILTRONICS SD25-470
M1, M3, M5: INFINEON BSC039N06NS
M2, M4, M6: VISHAY SILICONIX Si7113DN
V
IN
ISN1-3
GATE1 SENSEP1 SENSEN1 TG1
R1
8mΩ
R3
8mΩ
R5
8mΩ
M2 M4
M3
M6
M5
M1
D1
D4*
V
LED1
+
D5*
V
LED2
+
D6*
V
LED3
+
D2 D3
C
OUT1
4.7µF
100V
×3
C
OUT2
4.7µF
100V
×3
C
OUT3
4.7µF
100V
×3
R6
250mΩ
L1
10µH
L2
10µH
L3
10µH
GATE2 SENSEP2 SENSEN2 TG2
LT3797
GATE3 SENSEP3 SENSEN3 TG3
1A
50V
ISN3
ISP3
R4
250mΩ
ISN2
ISP2
R2
250mΩ
ISN1
ISP1
1A
50V
1A
50V
1M
140k
V
IN
0.1µF
(OPTIONAL)
0.1µF
(OPTIONAL)
0.1µF
(OPTIONAL)
