CS47L85 datasheet(355/370 Pages) CIRRUS

355 / 370 page

CS47L85

Rev 4.3

355

POWER SUPPLY / REFERENCE 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 (‘spikes’) in the power supply voltage can cause

malfunctions and unintentional behaviou

r in other components. A decoupling (‘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 CS47L85, these

variations can alter the performance of the signal path, leading to degradation in signal quality. A decoupling 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.

The recommended power supply decoupling capacitors for CS47L85 are detailed below in Table 136.

POWER SUPPLY

DECOUPLING CAPACITOR

LDOVDD, DBVDD1, DBVDD2, DBVDD3

0.1

F ceramic (see Note)

AVDD1, AVDD2

1.0

F ceramic

CPVDD

4.7

F ceramic

CPVDD2

4.7

F ceramic

MICVDD

4.7

F ceramic

DCVDD, FLLVDD

4 x 1.0

F ceramic - one close to each pin.

Alternatively, a single 4.7

F ceramic.

SPKVDDL, SPKVDDR

4.7

F ceramic

VREFC

2.2

F ceramic

Table 136 Power Supply Decoupling Capacitors

Note: 0.1

F is required with 4.7F a guide to the total required power rail capacitance.

All decoupling capacitors should be placed as close as possible to the CS47L85 device. The connection between AGND,

the AVDD decoupling capacitor and the main system ground should be made at a single point as close as possible to the

AGND balls of the CS47L85.

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.

CS47L85 Datasheet(PDF) 355 Page - Cirrus Logic

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