CS4207-CNZ Datasheet, PDF (144/148 Pages) Cirrus Logic – Low-power, 4-in / 6-out HD Audio Codec with Headphone Amp

8. PCB LAYOUT CONSIDERATIONS
CS4207
8.1 Power Supply, Grounding
As with any high-resolution converter, the CS4207 requires careful attention to power supply and grounding
arrangements if its potential performance is to be realized. Figure 1 on page 11 and Figure 2 on page 12
show the recommended power arrangements, with VA connected to a clean supply. VD, which powers the
digital circuitry, may be run from the system logic supply.
To achieve full analog performance, it is strongly recommended that the following rules be followed:
• place the cap between VBIAS and VA_REF as close to the codec as possible to minimize trace imped-
ance
• keep the traces for VA and VA_REF separate as much as possible and only connect them at the supply
Extensive use of power and ground planes, ground plane fill in unused areas and surface mount decoupling
capacitors are recommended. Decoupling capacitors should be as close to the pins of the CS4207 as pos-
sible. The low value ceramic capacitor should be closest to the pin and should be mounted on the same
side of the board as the CS4207 to minimize inductance effects. All signals, especially clocks, should be
kept away from the FILT+ and VCOM pins in order to avoid unwanted coupling into the modulators. The
CDB4207 evaluation board demonstrates the optimum layout and power supply arrangements.
8.2 QFN Thermal Pad
The CS4207 is available in a compact QFN package. The underside of the QFN package reveals a large
metal pad that serves as a thermal relief to provide for maximum heat dissipation. This pad must mate with
an equally dimensioned copper pad on the PCB and must be electrically connected to ground. A series of
vias should be used to connect this copper pad to one or more larger ground planes on other PCB layers.
In split ground systems, it is recommended that this thermal pad be connected to AGND for best perfor-
mance. The CDB4207 evaluation board demonstrates the optimum thermal pad and via configuration.
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