SC415 Semtech Corporation, SC415 Datasheet - Page 22

• Manufacturer Part Number: SC415
• Description: Dual Synchronous Buck Controller
• Manufacturer: Semtech Corporation

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Applications Information (continued)
Layout Guidelines
As with any switch-mode converter, and especially a
dual-channel converter, a good pcb layout is essential for
optimum performance. The following guidelines should
be used for pcb layout.
Placement
Note that the pins on the IC are arranged in four groups,
i.e. Side1 Power, Side2 Power, Side1 Analog, and Side2
Analog, as shown below.
For placement, power devices for side1 should be grouped
together near the gate drive pins for side1 (pins 23-24 and
1-8). Power devices for side2 should be grouped together
near the gate-drive pins for side2 (pins 15-20).
The feedback and VOUT sense components should
be located near the FBx/VOUTx pins. This includes the
feedback resistors and capacitors if used.
Power/Gate
Side 1
Drive
Analog
Side 1
VDD1
BST1
EN1
SS1
DL1
LX1
1
6
24
7
Figure 17
SC415
(PAD)
GND
19
12
18
13
Power/Gate
BST2
DL2
SS2
LX2
VDD2
EN2
Analog
Side 2
Side 2
Drive
Ground Connections
When doing placement, be aware that there are four
grounds.
1.
2.
3.
4.
Note that grounds (1) and (2) are high-current and contain
high noise. These grounds carry the DL gate drive current
as well as the high switching current through the MOSFETs
and low-side diode. It is important to note that the SC415
has only one power ground pin (PAD, pin 25), which must
drive DL for both side1 and side2. As such, the low-side
MOSFET and diode will need to be near the IC.
Grounds (3) and (4) are low-current and intended for low-
noise VOUT/FB ripple sensing. Note that there is only one
analog ground pin (RTN, pin 9) which shared between
sides 1 and 2.
Proper connection between the grounds is needed
for good operation. Generally, all ground connections
between the power components and the SC415 should
be short and direct, without vias where possible. Each
side has signifi cant high-current switching in the ground
path, moving between the input capacitors, the low-
side MOSFET, the low-side diode if used, and the output
capacitors. Moreover, each side has signifi cant high-
current pulses to/from the ground PAD, created by the DL
drive to the low-side MOSFETs. The DL gate-drive current
peaks can be 2 amps or more, with fast switching. As such
the ground connection between the low-side MOSFETs
and the ground PAD should be as short and wide as
practical.
Note that the ground PAD, which is the return path for
the high-noise DL drive current, is not accessible on the
top layer of the pcb, due to the other pins. The ground
Power ground for Side1
Power ground for Side2
Analog ground for Side1
Analog ground for Side2
SC415
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