LT3782 Linear Technology, LT3782 Datasheet - Page 13

• Manufacturer Part Number: LT3782
• Description: 2-Phase Step-Up DC/DC Controller
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
5. Losses in the boost diode. The power dissipation in the
6. Other losses, including C
PCB Layout Considerations
To achieve best performance from an LT3782 circuit, the
PC board layout must be carefully done. For lower power
applications, a two-layer PC board is sufficient. However,
at higher power levels, a multiplayer PC board is recom-
mended. Using a solid ground plane under the circuit is the
easiest way to ensure that switching noise does not affect
the operation.
boost diode is:
The boost diode can be a major source of power loss in
a boost converter. For 13.2V input, 42V output at 3A, a
Schottky diode with a 0.4V forward voltage would
dissipate 600mW, which represents about 1% of the
input power. Diode losses can become significant at
low output voltages where the forward voltage is a
significant percentage of the output voltage.
inductor core losses, generally account for less than
2% of the total losses.
P
DIODE
=
I
O MAX
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2
U
)
•
V
U
D
IN
and C
O
W
ESR dissipation and
U
In order to help dissipate the power from MOSFETs and
diodes, keep the ground plane on the layers closest to the
layers where power components are mounted. Use power
planes for MOSFETs and diodes in order to improve the
spreading of the heat from these components into the
PCB.
For best electrical performance, the LT3782 circuit should
be laid out as follows:
Place all power components in a tight area. This will
minimize the size of high current loops. Orient the input
and output capacitors and current sense resistors in a way
that minimizes the distance between the pads connected
to ground plane.
Place the LT3782 and associated components tightly
together and next to the section with power components.
Use a local via to ground plane for all pads that connect to
ground. Use multiple vias for power components.
Connect the current sense inputs of LT3782 directly to the
current sense resistor pads. Connect the current sense
traces on the opposite sides of pads from the traces
carrying the MOSFETs source currents to ground. This
technique is referred to as Kelvin sensing.
LT3782
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