CS4811 datasheet(16/24 Pages) CIRRUS

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CS4811

DS486PP2

4. POWER SUPPLY AND GROUNDING

Proper layout and grounding is critical to obtaining

optimal audio performance in your system. The

most important rule to remember is to not allow

currents from digital circuitry to couple into sensi-

tive analog circuitry. This is generally done by us-

ing a separate or filtered power supply for the

analog circuitry, physically separating the analog

and digital components and traces in the pcb layout

and using wide traces or planes for ground and

power. One misplaced component or trace can se-

verely degrade overall system performance.

When using separate supplies, the analog and digi-

tal power should be connected via a ferrite bead,

positioned closer than 1" to the device (see

Figure 11). The CS4811 VA pin should be derived

from the quietest power source available. If only

one supply is available, use the suggested arrange-

ment in Figure 3.

A single solid ground plane is the simplest ground-

ing scheme that works well in many cases. In this

case, all analog and digital grounds shown in

Figure 3 are tied to the same ground plane. Howev-

er, if separate analog and digital grounds are used,

they should be tied together at one point with the

location of this point determined by the circuit lay-

out. By considering where the digital ground cur-

rents will return to their supply, the connection

point can be chosen to keep those currents from

flowing through sensitive analog circuit areas.

Decoupling capacitors should be placed as close as

possible to the device with the lowest value capac-

itor closest to the chip. Any power and ground con-

nection vias should be placed near their respective

component pins and should be attached directly to

the appropriate plane. If traces are used for the

power supplies to the CS4811, they should be as

wide as possible to maintain low impedance.

It is recommended to solder the CS4811 directly to

the printed circuit board. Soldering improves per-

formance and enhances reliability.

For an example layout, please refer to the

CDB4811 data sheet.

Digital

Power

Plane

Note that the CS4811

is oriented with its

digital pins towards the

digital end of the board.

Digital Interface

Analog Signals &

Components

Analog

Power

Plane

1/8"

CS4811

Ferrite

Bead

Figure 11. CS4811 Suggested Layout

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