Datasheet

LTC3862-1
32
38621f
APPLICATIONS INFORMATION
Figure 25a. A 8.5V to 36V Input, 72V/2A Output 2-Phase Boost Converter Application Circuit
Figure 25b. Output Current vs Input Voltage
INPUT VOLTAGE (V)
0
0.5
0
OUTPUT LOAD CURRENT (A)
1.0
1.5
2.0
2.5
10 20 30 40
38621 F25b
4. A ripple current of 40% is chosen so the peak current
in each inductor is:
I
IN(PK)
=
1
n
•1–

2






•
I
O(MAX)
1–D
MAX
=
1
2
•1+
0.4
2






•
1.5A
1– 0.669
= 2.7A
5. The inductor ripple current is:
ΔI
L
=
χ
n
•
I
O(MAX )
1–D
MAX
=
0.4
2
•
1.5A
1– 0.669
= 0.9A
6. The inductor value is therefore:
L =
V
IN(MIN)
ΔI
L
•f
•D
MAX
=
24V
0.9A • 300kHz
• 0.669
= 59.5µH
7. For a current limit value 30% higher than the maximum
load current:
I
O(CL)
= 1.3 • I
O(MAX)
= 1.3 • 1.5A = 1.95A
The saturation current rating of the inductors must
therefore exceed:
I
L(SAT)

1
n
•1+

2






•
1.3 •I
O(MAX)
1–D
MAX
=
1
2
•1+
0.4
2






•
1.3 • 1.5A
1–
0.669
= 3.5A
SENSE1
+
3V8
SLOPE
BLANK
CLKOUT
SYNC
PLLFLTR
PHASEMODE
D
MAX
10nF
SENSE1
–
SENSE2
–
SENSE2
+
RUN
FREQ
SS
V
IN
45.3k 24.9k
150k
10
V
IN
8.5V TO 36V
D1
MURS320T3H
D2
MURS320T3H
10
L2
58µH
PA2050-583
ITH
SGND
V
OUT
5.62k
FB
45.3k
324k
0.1µF
1µF
1nF
6.8µF 50V
0.020
1W
Q1
HAT2267H
Q2
HAT2267H
0.020
1W
V
OUT
72V
2A (MAX)
38621 F25a
47µF
100V
47µF
100V
6.8µF 50V
6.8µF 50V
2.2µF
100V
×6
LTC3862-1
1.5nF
100pF
INTV
CC
GATE1
GATE2
PGND
4.7µF
10nF
L1
58µH
PA2050-583
+
+