ltc3717-1 Linear Technology Corporation, ltc3717-1 Datasheet - Page 17

• Manufacturer Part Number: ltc3717-1
• Description: Wide Operating Range, No Rsense Step-down Controller For Ddr/qdr Memory Termination
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
• The ground plane layer should not have any traces and
• Place C
• Place LTC3717-1 chip with Pins 15 to 28 facing the
• Use an immediate via to connect the components to
• Use compact plane for switch node (SW) to improve
• Use planes for V
• Flood all unused areas on all layers with copper. Flood-
it should be as close as possible to the layer with power
MOSFETs.
compact area. It may help to have some components on
the bottom side of the board.
power components. Keep the components connected
to Pins 1 to 10 close to LTC3717-1 (noise sensitive
components).
ground plane including SGND and PGND of LTC3717-1.
Use several bigger vias for power components.
cooling of the MOSFETs and to keep EMI down.
filtering and to keep power losses low.
ing with copper will reduce the temperature rise of
power component. You can connect the copper areas to
any DC net (V
your system).
IN
, C
OUT
IN
C
C
C
ION
, MOSFETs, D1 and inductor all in one
SS
C1
, V
IN
U
OUT
R
C
and V
FB
C
, GND or to any other DC rail in
U
BOLD LINES INDICATE HIGH CURRENT PATHS
OUT
C
C2
R
to maintain good voltage
ON
RUN/SS
PGOOD
V
I
SGND
I
V
V
V
W
TH
ON
RNG
ON
FB
REF
LTC3717-1
SENSE
SENSE
EXTV
BOOST
INTV
DRV
PGND
Figure 8. LTC3717-1 Layout Diagram
V
SW
BG
TG
CC
CC
CC
CC
+
–
U
C
VCC
C
D
B
B
C
When laying out a printed circuit board, without a ground
plane, use the following checklist to ensure proper opera-
tion of the controller. These items are also illustrated in
Figure 8.
• Segregate the signal and power grounds. All small
• Place M2 as close to the controller as possible, keeping
• Connect the input capacitor(s) C
• Keep the high dV/dT SW, BOOST and TG nodes away
• Connect the INTV
• Connect the top driver boost capacitor C
• Connect the V
F
R
signal components should return to the SGND pin at
one point which is then tied to the PGND pin close to the
source of M2.
the PGND, BG and SW traces short.
MOSFETs. This capacitor carries the MOSFET AC cur-
rent.
from sensitive small-signal nodes.
C
BOOST and SW pins.
the V
F
VCC
CC
closely to the INTV
M2
and PGND pins.
C
OUT
D1
CC
D2
M1
L
pin decoupling capacitor C
CC
C
and DRV
IN
CC
37171 F08
, DRV
CC
CC
IN
decoupling capacitor
LTC3717-1
close to the power
+
–
–
+
and PGND pins.
V
V
IN
OUT
B
closely to the
F
sn37171 37171fs
closely to
17