LT3579/LT3579-1
TYPICAL APPLICATION
500kHz SEPIC Converter Generates 3.3V from a 3V to 33V Input
VBAT
3V TO 33V (OPERATING)
6V TO 16V (START-UP)
200k
C1
10nF
D1
15V
Q1
D3
L1
• 3.3μH
CPWR
4.7μF
s2
M1
100k
CVIN
10μF
174k
SW1 SW2
VIN
FB
SHDN
GATE
LT3579
FAULT
VC
RT
CLKOUT
SYNC GND SS
C2
4.7μF
D2
D4
L2
3.3μH
10k
•
4.7nF
24.9k
100pF
8.25k
10k
VOUT
3.3V
1.8A (VBAT = 3V)
3.1A (VBAT = 9V)
3.4A (VBAT ≥ 12V)
COUT
47μF
s6
0.22μF
4.7nF
C1: 10nF, 16V, X7R, 0603
CVIN: 10μF, 16V, X7R, 1206
CPWR, C2: 4.7μF, 50V, X7R, 1210
COUT: 47μF, 6.3V, X7R, 1210
D1: CENTRAL SEMI CMHZ5245B-LTZ
D2: VISHAY SS5P6
D3: CENTRAL SEMI CMMSH2-40
D4: CENTRAL SEMI CMMSH2-40
L1, L2: WÜRTH WE-DD 744870003
M1: 2N7002
Q1: MMBT3904
3579 TA07a
Efficiency and Power Loss
90
4
80
3.5
70
3
60
50
VBAT = 3V
2.5
VBAT = 12V
2
40
1.5
30
1
20
0.5
10
0
0 0.5 1 1.5 2 2.5 3 3.5 4
LOAD CURRENT (A)
3579 TA08a
Transient Response with 9V to 33V to 9V VBAT Glitch (RLOAD = 1.5Ω)
VOUT
2V/DIV
VBAT
10V/DIV
IL1 + IL2
1A/DIV
50ms/DIV
3579 TA08b
35791f
32