PAM8001

Document number: DSxxxxx Rev. 1 - 0

13 of 17

www.diodes.com

February 2013

© Diodes Incorporated

PAM8001

A Product Line of

Diodes Incorporated

How to Reduce EMI (Electro Magnetic Interference)

A simple solution is to put an additional capacitor 1000uF at power supply terminal for power line coupling if the traces from amplifier to

speakers are short (<20CM).

Most applications require a ferrite bead filter as shown at Figure 1. The ferrite filter reduces EMI around 1 MHz and higher. When selecting a

ferrite bead, choose one with high impedance at high frequencies, and low impedance at low frequencies (MH2012HM221-T).

Figure 1 Ferrite Bead Filter to Reduce EMI

PCB Layout Guidelines Grounding

At this stage it is paramount to notice the necessity of 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 cases 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 channel amplifier has two seperate channels and consequently must have two seperate output

noise ground traces. The layout of the PAM8001 offers separate PGND connections for each channel and in some cases each side of the

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

returned to quite ground. This ground is only tied to the signal components and the GND pin, and GND then tied to system ground.

PCB Layout Example

Figure 2 Top Layer