CS6422
CS6422
Figure 8 shows the suggested placement of decou- from digital, as shown in Figure 9. The ferrite bead
pling capacitors for the power supplies. Note that
the trace length from the power pin to the capaci-
serves as a low-pass filter to remove CS6422 digi-
tal switching noise from the analog power supply.
tors is minimized. Also note that the smaller valued The ground is separated by isolating all the digital
capacitor is placed closer to the pin than the larger
valued capacitor. The smaller capacitor decouples
components of the system board on one ground
plane and all the analog and linear components on
high frequency noise and the larger capacitor atten- a different ground plane. The CS6422 should be
uates lower frequencies.
placed over the analog ground plane. This prevents
digital switching noise from the digital components
of the board from coupling into the converters and
aliasing into the passband.
The separation of analog and digital power and
ground is done in two ways. The power is separated
by deriving the digital power for the CS6422 from
the analog through a ferrite bead to isolate analog
Ferrite Bead
+5V
(Analog)
AVDD
AGND
DVDD
CS6422
DGND
10
µ
F
0.1
µ
F
0.1 F 10 µ F
µ
Analog Ground Plane
Digital Ground Plane
Microcontroller
Figure 9. Ground Planes
31
31
DS295F1
CIRRUS [ CIRRUS LOGIC ]
