CS6422-CSZ datasheet(30/48 Pages) CIRRUS

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CS6422

3.11

Power Supply

The pins AVDD (pin 1) and AGND (pin 2) power

the analog sections of the CS6422, and DVDD (pin

16) and DGND (pin 15) power the digital sections.

This distinction is important because internal to the

part, the digital power supply is likely to contain

high-frequency energy. The analog power supply is

kept clean internally by drawing current from a dif-

ferent pin, thereby achieving high performance in

the codecs and the microphone preamplifier.

The digital supply of the CS6422 should not be

connected to the system digital supply, if there is

one, as the CS6422 has internal timing mechanisms

designed to minimize the detrimental effects of its

own digital noise, but cannot use these to compen-

sate for externally introduced digital noise. The

CS6422 digital power supply should be derived

from its analog power supply through a ferrite bead

with low (< 1

Ω) DC impedance.

3.11.1

Power Down Mode

Typical power consumption of the CS6422 is

60 mA, assuming normal operating conditions.

This current consumption can be further reduced

by invoking the powerdown mode, which is en-

tered by holding RST low. Holding RST low will

power down all the internal blocks of the CS6422

and stop the oscillator. In powerdown mode, cur-

rent consumption drops to less than 2 mA.

3.11.2

Noise and Grounding

Since the CS6422 is a mixed-signal integrated cir-

cuit, the system designer must pay special attention

to layout and decoupling to minimize noise cou-

pling. The three best methods to reduce noise when

using the CS6422 are to properly decouple the

power supplies, to separate the system analog and

digital power and ground (all power and ground

pins of the CS6422 should tie to the analog power

supply), and to route signals on the board carefully.

AGND

DVDD

AVDD

+5V

Analog

Supply

DGND

From

Ferrite

Bead

Figure 8. Suggested Layout

CS6422

DS295F1

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