Cirrus Logic CRD5376 - Manual (Page 30)

CRD5376
30 DS612RD2
CRD5376 layer 5 is a solid ground plane without splits or routing. A solid ground plane provides the best
return path for bypassed noise to leave the system. No separate analog ground is required since analog
signals on CRD5376 are differentially routed.
CRD5376 layer 6 is dedicated for analog and digital routing. Critical analog signal routes for channels 3
and 4 are on this layer. Some digital routes for the microcontroller are also included on this layer away
from the analog signal routes.
2.5.2 Differential Pairs
Analog signal routes on CRD5376 are differential with dedicated + and - traces. All source and return an-
alog signal currents are constrained to the differential pair route and do not return through the ground
plane. Differential traces are routed together with a minimal gap between them so that noise events affect
them equally and are rejected as common mode noise.
Analog signal connections into the CS3301A/02A amplifiers are 2-wire IN+ and IN- differential pairs, and
are routed as such. Analog signal connections out of the CS3301A/02A amplifiers and into the CS5372A
modulators are 4-wire INR+, INF+, INF-, INR- quad groups, and are routed with INF+ and INF- as a tra-
ditional differential pair and INR+ and INR- as guard traces outside the respective INF+ and INF- traces.
Figure 2. Differential Pair Routing
Figure 3. Quad Group Routing
INR-
INF-
INF+
INR+