Linear Technology LT3956 Series, Manual, Page: 18 / 20

LT3956
3956f
90% Efficient, 20W SEPIC LED Driver
V
IN
LT3956
L1A
33µH
1:1
GND V
C
INTV
CC
EN/UVLO SW
V
REF
ISP
100k
INTV
CC
1M
C1
4.7µF
50V
10nF 0.01µF
L1: COILTRONICS DRQ127-330
D1: VISHAY PDS5100
M1: ZETEX ZXM61N03F
V
IN
8V TO
50V
185k
250k
25k
C3
10µF
s 2
35V
PGND
L1B
15k
28.7k
375kHz
C2
4.7µF
10V
CTRL
1M
0.25Ω
M1
1A
D1
C4
2.2µF (50V)
20W
LED
STRING
CURRENT
DERATED
FOR V
IN
< 13V
3956 TA05a
VMODE
PWM
SS
RT
ISN
FB
PWMOUT
56.2k
V
IN
(V)
0 10
80
EFFICIENCY (%)
84
88
92
96
100
30 40
3956 TA05b
20 50
Typical applicaTions
Efficiency vs V
IN
90W Buck Mode LED Driver, 80V
IN
/60V
OUT
V
IN
V
IN
LT3956
GND V
C
INTV
CC
V
REF
INTV
CC
EN/UVLO
SW
ISP
100k
INTV
CC
1M
0.01µF 0.1µF
D1: VISHAY 10MQ100N
L1: WÜRTH ELEKTRONIK 744066330
M1: VISHAY SILICONIX Si7113DN
Q1: ZETEX FMMT593
Q2: ZETEX FMMT493
C1, C2: MURATA GRM42-2x7R225
V
IN
64V TO
80V
20k
28.7k
375kHz
4.7µF
0.1Ω
1.5A
16 WHITE
LEDs, 90W
3956 TA06a
VMODE
PWM
CTRL
SS
RT PGND
ISN
FB
PWMOUT
C1
2.2µF
s 4
C2
2.2µF
s 3
267k 200k
10k
Q1
M1
D1
L1
33µH
200k
470Ω
1k
Q2
24.3k
13k
V
IN
(V)
64
90
EFFICIENCY (%)
92
94
96
98
100
72 76
3956 TA05b
68 80
Efficiency vs V
IN