PAM8407

Document number: DS36815 Rev. 1 - 2

9 of 12

www.diodes.com

January 2014

© Diodes Incorporated

PAM8407

A PRODUCT LINE OF

DIODES INCORPORATED

2x3W Stereo Differential Input Class D Audio Amplifier

with Up/Down Volume Control

220pF

220pF

OUT+

OUT-

Ferrite Bead

Ferrite Bead

Figure 3: Ferrite Bead Filter to reduce EMI

PCB Layout Guidelines

Grounding

At this stage it is paramount that we acknowledge the need for separate grounds. Noise currents in the output power stage need to be returned to

output noise ground and nowhere else. Were these currents to circulate elsewhere, they may get into the power supply, the signal ground, etc,

worse yet, they may form a loop and radiate noise. Any of these instances results in degraded amplifier performance. The logical returns for the

output noise currents associated with Class D switching are the respective PGND pins for each channel. The switch state diagram illustrates that

PGND is instrumental in nearly every switch state. This is the perfect point to which the output noise ground trace should return. Also note that

output noise ground is channel specific. A two channels amplifier has two mutually exclusive channels and consequently must have two mutually

exclusive output noise ground traces. The layout of the PAM8407 offers separate PGND connections for each channel and in some cases each

side of the bridge. Output noise grounds must tie to system ground at the power in exclusively. Signal currents for the inputs, reference, etc need

to be returned to quite ground. This ground only ties to the signal components and the GND pin. GND then ties to system ground.

Power Supply Line

As same to the ground, VDD and each channel PVDD need to be separated and tied together at the system power supply. Recommend that all

the trace could be routed as short and thick as possible. For the power line layout, just imagine water stream, any barricade placed in the trace

(shows in figure 4) could result in the bad performance of the amplifier.

Figure 4

Components Placement

The power supply decoupling capacitors need to be placed as close to VDD pins as possible. The inputs need to be routed away from the noisy

trace.