PAM8803 datasheet(11/13 Pages) PAM

11 / 13 page

Most applications require a ferrite bead filter

which shows at Figure 3. The ferrite filter

reduces EMI around 1 MHz and higher. When

selecting a ferrite bead, choose one with high

impedance a t high frequencies, but low

impedance at low frequencies.

Figure 3: Ferrite Bead Filter to reduce EMI

this

stage

paramount

that

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

m utually

exclusive

c hannels

and

consequently must have two mutually exclusive

output noise ground traces. The layout of the

PAM8803 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.

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

The power supply decoupling capacitors need to

be placed as close to VDD and PVDD pins as

possible. The inputs need to be routed away from

the noisy trace. The VREF bypass capacitor also

needs to be close to the pin of IC very much.

PCB Layout Guidelines

Grounding

Power Supply Line

Components Placement

220pF

OUT+

OUT-

Ferrite Bead

Power Analog Microelectronics Inc

www.poweranalog.com

Figure 5: Layout Example

PCB Top Layer

PCB Bottom Layer

PAM8803

3W Filterless Stereo Class-D Audio Amplifier

with Digital Volume Control

12/2009 Rev 1.4

PAM8803 Datasheet(PDF) 11 Page - Power Analog Micoelectronics

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