MP3378

– 4-CHANNEL WLED CONTROLLER PLUS BUCK CONVERTER

MP3378 Rev. 1.01

www.MonolithicPower.com

22

5/26/2017

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PCB Layout Guidelines

Efficient PCB layout is critical to reduce EMI

noise. For best results, refer to Figure 9 (boost

driver layout) and Figure 10 (buck converter

layout) and follow the guidelines below:

Boost Driver Layout (see Figure 9)

1) Make the loop from the external MOSFET

(M1), through the output diode (D1) and the

output capacitors (C2, C3) as small and short

as possible as they carry a high-frequency

pulse current.

2) Separate the power ground and signal ground

and then connect PGND and GND together

as all logic signals refer to the signal ground.

This reduces the noise affection.

Buck Converter Layout (see Figure 10)

1) Keep the connection of the input ground and

GND2 (PGND) as short and wide as possible.

2) Keep the connection of the input capacitors

(C16, C16A, and C17) and VIN2 as short and

wide as possible.

3) Ensure all feedback connections are short

and direct. Place the feedback resistors and

compensation components as close to the

chip as possible.

4) Route SW away from sensitive analog areas

such as FB.

5) Connect a resistor (R23) to AGND as SYN is

sensitive to noise. Otherwise SCP may fail,

and the buck converter may be damaged.

6) Connect GND1 and GND2 together by a

single point.

Figure 9

—Recommended boost driver layout

Figure 10

—Recommneded buck converter layout