20

DS786A1

CS4412A

5. POWER SUPPLY, GROUNDING, AND PCB LAYOUT

5.1

Power Supply and Grounding

The CS4412A requires careful attention to power supply and grounding arrangements if its potential perfor-

mance is to be realized.

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

capacitors are recommended. It is necessary to decouple the power supply by placing capacitors directly

between the power and ground of the CS4412A. Decoupling capacitors should be as close to the pins of

the CS4412A as possible. The lowest value ceramic capacitor should be closest to the pin and should be

mounted on the same side of the board as the CS4412A to minimize inductance effects. The CRD4412A

reference design demonstrates the optimum layout and power supply arrangements.

5.1.1

Integrated VD Regulator

The CS4412A includes an internal linear regulator to provide a fixed 2.5 V supply from the VD supply volt-

age for its internal digital logic. The LVD pin must be set to indicate the voltage present on the VD pin as

shown in Table 9 below.

Table 9. Power Supply Configuration and Settings

The output of the digital regulator is presented on the VD_REG pin and may be used to provide an exter-

nal device with up to 3mA of current at its nominal output voltage of 2.5 V.

If a nominal supply voltage of 2.5 V is used as the VD supply (see the Recommended Operating Condi-

tions table on page 5), the VD and VD_REG must be connected to the VD supply source. In this config-

uration, the internal regulator is bypassed and the external supply source is used to directly drive the

internal digital logic.

5.2

QFN Thermal Pad

The CS4412A 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

thermal vias should be used to connect this copper pad to one or more larger ground planes on other PCB

layers; the copper in these ground planes will act as a heat sink for the CS4412A. The CRD4412A reference

design demonstrates the optimum thermal pad and via configuration.

VD Connection

VD_REG Connection

LVD Connection

5 V Supply

Bypass Capacitors Only

VD

3.3 V Supply

Bypass Capacitors Only

GND

2.5 V Supply

VD and Bypass Capacitors

GND