Datasheet

LTC3127
15
3127f
SW1 SW2
VIA TO
GROUND
V
IN
V
OUT
SHDN
MODE
PROG
SGND
PGND
FB
V
C
VIA TO
GROUND
3127 F04
10
9
6
7
8
4
5
3
2
1
Figure 4. Recommended PCB Layout
applicaTions inForMaTion
PCB Layout Considerations
The LTC3127 switches large currents at high frequencies.
Special care should be given to the PCB layout to ensure
stable, noise-free operation. Figure 4 depicts the recom-
mended PCB layout to be utilized for the LTC3127. A few
key guidelines follow:
1. All circulating high current paths should be kept as short
as possible. This can be accomplished by keeping the
routes to all bold components in Figure 4 as short and
as wide as possible. Capacitor ground connections
should via down to the ground plane in the shortest
route possible. The bypass capacitor on V
IN
should be
placed as close to the IC as possible and should have
the shortest possible path to ground.
2. The small-signal ground pad (SGND) should have a
single point connection to the power ground. A con-
venient way to achieve this is to short the pin directly
to the Exposed Pad as shown in Figure 4.
3. The components shown in bold and their connections
should all be placed over a complete ground plane.
4. To prevent large circulating currents from disrupting
the output voltage sensing, the ground for the resistor
divider and R
PROG
should be returned directly to the
small signal ground pin (SGND).
5. Use of vias in the die attach pad will enhance the ther-
mal environment of the converter especially if the vias
extend to a ground plane region on the exposed bottom
surface of the PCB.
6. Keep the connections to the FB and PROG pins as
short as possible and away from the switch pin con-
nections.