lt3958 Linear Technology Corporation, lt3958 Datasheet - Page 22

• Manufacturer Part Number: lt3958
• Description: High Input Voltage, Boost, Flyback, Sepic And Inverting Converter
• Manufacturer: Linear Technology Corporation

LT3958
APPLICATIONS INFORMATION
• In fl yback confi guration, the high di/dt primary loop
• In SEPIC confi guration, the high di/dt loop con-
• In inverting confi guration, the high di/dt loop con-
Check the stress on the internal power MOSFET by measur-
ing the SW-to-GND voltage directly across the IC terminals.
22
contains the input capacitor, the primary winding,
the internal power MOSFET. The high di/dt second-
ary loop contains the output capacitor, the secondary
winding and the output diode.
tains the internal power MOSFET, output capacitor,
Schottky diode and the coupling capacitor.
tains internal power MOSFET, Schottky diode and the
coupling capacitor.
Figure 9. Suggested Layout of the 10V to 40V Input, 48V Output Boost Converter
V
L1
IN
C
IN
GND
10
1
2
3
4
6
8
9
VIAS TO SGND GROUND PLANE
VIAS TO SW PLANE
36 35 34 33 32 31 30
12 13 14 15 16 17
C
Make sure the inductive ringing does not exceed the
maximum rating of the internal power MOSFET (84V).
The small-signal components should be placed away from
high frequency switching nodes. For optimum load regula-
tion and true remote sensing, the top of the output voltage
sensing resistor divider should connect independently to
the top of the output capacitor (Kelvin connection), staying
away from any high dV/dt traces. Place the divider resis-
tors near the LT3958 in order to keep the high impedance
FBX node short.
Figure 9 shows the suggested layout of the 48V V
converter (see the Typical Applications section).
R1
R
C
SS
T
OUT
LT3958
37
38
R2
C
VIA TO V
V
OUT
OUT
R
C
28
27
25
24
23
21
20
OUT
C
R4
C
C
VIA TO V
VCC
R3
D1
OUT
3958 F09
OUT
boost
3958f