Datasheet

LT8614
12
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APPLICATIONS INFORMATION
Low EMI PCB Layout
The LT8614 is specifically designed to minimize EMI
emissions and also to maximize efficiency when switching
at high frequencies. For optimal performance the LT8614
requires the use of multiple V
IN
bypass capacitors.
Two small 1µF capacitors should be placed as close as
possible to the LT8614: One capacitor should be tied to
V
IN1
/GND1; a second capacitor should be tied to V
IN2
/
GND2. A third capacitor with a larger value, 2.2µF or
higher, should be placed near V
IN1
or V
IN2
.
See Figure1 for a recommended PCB layout.
For more detail and PCB design files refer to the Demo
Board guide for the LT8614.
Note that large, switched currents flow in the LT8614
V
IN1
, V
IN2
, GND1, and GND2 pins and the input capacitors
(C
IN1
, C
IN2
). The loops formed by the input capacitors
should be as small as possible by placing the capacitors
adjacent to the V
IN1/2
and GND1/2 pins. Capacitors with
small case size such as 0603 are optimal due to lowest
parasitic inductance.
The input capacitors, along with the inductor and out-
put capacitors, should be placed on the same side of the
circuit board, and their connections should be made on
that layer. Place a local, unbroken ground plane under the
application circuit on the layer closest to the surface layer.
The SW and BOOST nodes should be as small as possible.
Finally, keep the FB and RT nodes small so that the ground
Figure1. Recommended PCB Layout for the LT8614
V
V
V
V
V
V
1
6
11
16
GROUND PLANE
ON LAYER 2
20
R1
R2
C
VCC
C
BST
C
IN1
C
IN2
C
IN3
C
OUT
L
R
T
C
SS
C1 R
PG
17
7 10
22
21
GROUND VIA V
IN
VIA V
OUT
VIA OTHER SIGNAL VIAS
9614 F01
V
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