WM3100

Preliminary Technical Data

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PTD, October 2010, Rev 2.0

10

RECOMMENDED EXTERNAL COMPONENTS

AUDIO INPUT PATHS

A DC-blocking input capacitor is required on each input pin that is used. A single capacitor is

required for a single-ended connection; for differential connection, a capacitor is required on both

input pins. Unused input pins must be connected to ground.

For typical applications, a 1

μF capacitor is recommended. Tantalum electrolytic capacitors are

particularly suitable as they offer high stability in a small package size.

AUDIO OUTPUT PATHS

An analogue low-pass filter is recommended on each line output. A simple RC filter comprising a

560Ω resistor and a 2.7nF capacitor is suitable. Ceramic capacitors with C0G / NP0 dielectric are

recommended.

POWER SUPPLY DECOUPLING

Power supply decoupling is required on VDD. A 4.7μF capacitor is recommended.

Decoupling capacitors should be placed as close as possible to the WM3100 device. The connection

between GND, the VDD decoupling capacitor and the main system ground should be made at a

single point as close as possible to the GND pin of the WM3100.

Due to the wide tolerance of many types of ceramic capacitors, care must be taken to ensure that the

selected components provide the required capacitance across the required temperature and voltage

ranges in the intended application. For most application the use of ceramic capacitors with capacitor

dielectric X5R is recommended.

CHARGE PUMP COMPONENTS

A fly-back capacitor is required between the CPCA and CPCB pins. The required capacitance is

2.2μF. A decoupling capacitor is required on CPVOUTN; the recommended value is 1μF.

The positioning of the charge pump capacitors is important, particularly the fly-back capacitor. The

use of short and wide PCB tracks for the fly-back capacitor connections will give best results due to

its low resistance. Both capacitors should be placed as close as possible to the WM3100.

Due to the wide tolerance of many types of ceramic capacitors, care must be taken to ensure that the

selected components provide the required capacitance across the required temperature and voltage

ranges in the intended application. For most application the use of ceramic capacitors with capacitor

dielectric X5R is recommended.