LTC3862_15 Datasheet, PDF (32/42 Pages) Linear Technology – Multi-Phase Current Mode Step-Up DC/DC Controller

LTC3862
Applications Information
45.3k
10nF
4.7nF
30.1k
100pF
12.4k
475k
V_OUT
1nF
D_MAX ^{3V8 GATE1}
SLOPE
SENSE1⁺
BLANK
PHASEMODE SENSE1^–
FREQ
RUN
SS
LTC3862 ^VIN
ITH
FB
INTV_CC
SGND
PGND
SENSE2^–
CLKOUT
SYNC
PLLFLTR
SENSE2⁺
GATE2
V_IN
5V TO 36V
L1
18.7µH
PB2020-223
D1
30BQ060
10nF
24.9k
1µF
84.5k
4.7µF
10nF
Q1
10Ω
HAT2266H
0.008Ω
1W
100µF
63V
6.8µF 50V
6.8µF 50V
6.8µF 50V
100µF _{10µF ×4 50V}
63V
10Ω
L2
18.7µH
PB2020-223
0.008Ω
1W
Q2
HAT2266H
D2
30BQ060
10µF ×4 50V
10µF ×4 50V
10µF ×4 50V
Figure 26a. A 5V to 36V Input, 48V/5A Output 2-Phase Boost Converter Application Circuit
V_OUT
48V
5A (MAX)
3862 F26a
6
5
4
3
2
1
0
0
10
20
30
40
INPUT VOLTAGE (V)
3862 F26b
Figure 26b. Output Current vs Input Voltage
The saturation current rating of the inductors must
therefore exceed:
I_L(SAT)
≥
1
n
•


1+
χ
2 
•
1.3 • I_O(MAX)
1– D_MAX

=
1
2
•


1+
0.4
2 
•
1.3 • 5A
1– 0.505
=
7.9A
The inductor value chosen was 18.7μH and the part
number is PB2020-223, manufactured by Pulse Engi-
neering. This inductor has a saturation current rating
of 20A.
8. The power MOSFET chosen for this application is
a Renesas HAT2266H. This MOSFET has a typical
R_DS(ON) of 11mΩ at V_GS = 4.5V and 9.2mΩ at V_GS
= 10V. The BV_DSS is rated at a minimum of 60V and
the maximum continuous drain current is 30A. The
typical gate charge is 25nC for a V_GS = 4.5V. Last but
not least, this MOSFET has an absolute maximum
avalanche energy rating EAS of 34mJ, indicating that
it is capable of avalanche without catastrophic failure.
9. The total IC quiescent current, IC power dissipation
and maximum junction temperature are approximately:
I_Q(TOT) = I_Q + 2 • Q_G(TOT) • f
= 3mA + 2 • 25nC • 300kHz = 18mA
P_DISS = 24V • 18mA = 432mW
T_J = 70°C + 432mW • 34°C/W = 84.7°C
3862fc
32
For more information www.linear.com/LTC3862