CS4216 Datasheet, PDF(50/58 Page) Cirrus Logic

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CS4216 Datasheet, PDF (50/58 Pages) Cirrus Logic – 16-Bit Stereo Audio Codec

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CDB4216

Notice in Figure 12 and Figure 13 how the

ground plane split is positioned. The split is

next to the part - NOT UNDER IT. The AGND

and DGND pins are connected to the ground

plane fill inside the codec pad layout on the

component-side layer. This is recommended be-

cause AGND and DGND are connected on the

codec die and must have a zero impedance be-

tween them.

Notice how each ground connection has at least

four points in thermal relief. The main board

grounds at the terminal connections have eight

points in thermal relief. This helps minimize the

impedance to the main ground terminal from any

particular ground pin, reducing the chance of

noise coupling.

Another important design consideration is the

ground plane fill between traces on both layers,

which minimizes coupling of radiated energy.

Ground fill on the digital side of the board helps

reduce the amount of noisy digital energy radi-

ated to the sensitive analog side and to a host

system. Ground fill on the analog side helps re-

duce the amount of radiated digital energy that is

coupled into the analog circuitry. All ground

plane fills must be connected to their respective

grounds - floating ground fill is worse than no

fill.

All power and ground traces are as thick as the

surface mount pads they connect. Thick traces

minimize impedance, thereby reducing the

chance of noise coupling.

Decoupling

Notice how the decoupling capacitors are placed

as close as possible to the codec. The 0.1ÂµF ca-

pacitors are placed closer than the 10ÂµF or 1ÂµF

capacitors. This reduces lead inductance at high

frequencies and allows the smaller valued ca-

pacitors to attenuate unwanted signals more

effectively.

Sockets

The CDB4216/8 was designed to accommodate

either the 44-pin PLCC package or the 44-pin

TQFP package. Each evaluation board is

shipped with a PLCC codec loaded into a sur-

face mount socket. Notice how the socket pads

match the footprint of the PLCC package. Using

this socket in a design allows for testing with the

socket mounted, and the option to surface mount

the codec directly for cost reduction during

board production.

DS83DB4

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