WM5102 Datasheet, PDF (320/334 Pages) Wolfson Microelectronics plc – Audio Hub CODEC with Voice Processor DSP

WM5102
Production Data
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
behavior 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 WM5102, 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 and voltage reference decoupling capacitors for WM5102 are
detailed below in Table 128.
POWER SUPPLY
LDOVDD, DBVDD1, DBVDD2, DBVDD3, AVDD
CPVDD
MICVDD
DCVDD
SPKVDDL, SPKVDDR
VREFC
Table 128 Power Supply Decoupling Capacitors
DECOUPLING CAPACITOR
0.1F ceramic (see Note)
4.7F ceramic
4.7F ceramic
4.7F ceramic
4.7F ceramic
1.0F ceramic
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 WM5102 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 WM5102.
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.
w
PD, June 2014, Rev 4.2
320