CS4399 datasheet(95/111 Pages) CIRRUS

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DS1113F1

CS4399

8 PCB Layout Considerations

The following sections provide general guidelines for PCB layout to ensure the best performance of the CS4399.

8.1 Power Supply

As with any high-resolution converter, the CS4399 requires careful attention to power supply and grounding arrangements

if its potential performance is to be realized. Fig. 2-1 shows the recommended power arrangements with VA and VCP

connected to independent clean supplies. VL and VD, which power the digital circuitry, may be run from the shared system

logic supply.

8.2 Grounding

Note the following:

• Extensive use of power and ground planes, ground-plane fill in unused areas, and surface-mount decoupling

capacitors are recommended.

• Decoupling capacitors must be as close as possible to the CS4399 pins.

• To minimize inductance effects, the low-value ceramic capacitor must be closest to the pin and mounted on the

same side of the board as the CS4399.

• To avoid unwanted coupling into the modulators, all signals, especially clocks, must be isolated from the FILT+ and

FILT- pins.

• The FILT+ capacitors must be positioned to minimize the electrical path from the pin to VA.

• The FILT– capacitors must be positioned to minimize the electrical path from the pin to –VA.

• The VCP_FILT+ and VCP_FILT– capacitors must be positioned to minimize the electrical path from each respective

pin to GNDCP.

8.3 REFA and REFB Routing

For best interchannel isolation performance, REFA and REFB must be routed independently to the headphone connector

reference pin. The REFA and REFB are electrically connected to system’s ground plane through via at the headphone

connector ground pin. Fig. 2-1 illustrates the recommended arrangements.

For interfacing the REFA and REFB pins with an IC that performs alternate pinout headset detect functions, both signals

must be routed independently to the CS4399’s ground pin connecting the detected headset ground pole. Follow the

recommended grounding scheme of the CS4399.

8.4 QFN Thermal Pad

The CS4399 comes in a compact QFN package, the underside of which reveals a large metal pad that serves as a thermal

relief to provide maximum heat dissipation. This pad must mate with an matching copper pad on the PCB and must be

electrically connected to ground. A series of vias must be used to connect this copper pad to one or more larger ground

planes on other PCB layers. For best performance in split-ground systems, connect this thermal pad to GNDA.

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