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Qorvo 1800MHz Small Cell RF Card Hardware User’s Guide
Hardware User’s Guide
5.2
Digital Isolation
The ZCU111 has digital components running at high frequencies, while the Qorvo RF card may be
sensitive to minor disturbances. It is therefore desirable to isolate the ZCU111 from RF noise and
to isolate RF signals on the Qorvo card from digital noise sources.
There are a number of possible power configurations, as discussed under Power Options. When
the ZCU111 and Qorvo card are powered separately as in the diagram below, the digital ground
from the ZCU111, DGND, is not connected to the
Qorvo card’s RF ground, RGND.
Note that
this
is not the factory default power configuration and that here external 5V to the Qorvo card
requires R140 and R141 to be removed
.
The digital isolators used to achieve separation are the Texas Instruments devices:
ISO7140 (4 channels forward) and
ISO7141 (3 channels forward, 1 channel back).
The Qorvo attenuators use 5V logic. The isolators can level shift between 3V and 5V. Since the
ZCU111 Zynq banks used for digital I/O are configured for 1.8V, separate level translators are used
to convert the Zynq signals to/from 3.3V, while the isolators level shift between 3.3V and 5V.
Figure 5
– External 5V configuration and Isolators for Separate DGND and RGND Domains
Figure 6
– Example Level Translation and Digital Isolation
