WM8948ECSSLASHR datasheet(183/189 Pages) WOLFSON

183 / 189 page

Production Data

WM8948

PD, May 2011, Rev 4.1

183

Figure 60 DC-blocking Components for Line Output

Figure 61 DC-blocking Components for Headphone Output

BTL SPEAKER OUTPUT CONNECTION

The BTL speaker output connection is a differential mode of operation. The loudspeaker may be

connected directly across the SPKOUTL and SPKOUTR pins. No additional external components are

required in this case.

POWER SUPPLY DECOUPLING

Electrical coupling exists particularly in digital logic systems where switching in one sub-system

causes fluctuations on the power supply. This effect occurs because the inductance of the power

supply acts in opposition to the changes in current flow that are caused by the logic switching. The

resultant variations (or ‘spikes’) in the power supply voltage can cause malfunctions and

unintentional behavior in other components. A decoupling (or ‘bypass’) capacitor can be used as an

energy storage component which will provide power to the decoupled circuit for the duration of these

power supply variations, protecting it from malfunctions that could otherwise arise.

Coupling also occurs in a lower frequency form when ripple is present on the power supply rail

caused by changes in the load current or by limitations of the power supply regulation method. In

audio components such as the WM8948, these variations can alter the performance of the signal

path, leading to degradation in signal quality. A decoupling (or ‘bypass’) capacitor can be used to

filter these effects, by presenting the ripple voltage with a low impedance path that does not affect

the circuit to be decoupled.

These coupling effects are addressed by placing a capacitor between the supply rail and the

corresponding ground reference. In the case of systems comprising multiple power supply rails,

decoupling should be provided on each rail.

WM8948ECS/R Datenblatt(PDF) 183 Page - Wolfson Microelectronics plc