UM4B0 User Manual
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3.5
Reset Signal
UM4B0 module can’t work properly unless it is correctly reset after power on. To
ensure effective reset, the reset pin (RST) and power supply pin (VCC) must meet the
following time sequence requirement. To reset UM4B0 during normal operation,
please pull RST pin to low level for more than 5ms.
VCC
RST
> 5ms
Figure 3-4 UM4B0 RST
3.6
Antenna
The module has the antenna input pin ANT_IN, which provides a +3.3V antenna feed.
When an active antenna of +3.3~5V is adopted, please make sure the 50 Ω antenna
impedance is matched.
ANT_IN
UM4B0 Module
Figure 3-5 UM4B0 Active Antenna Connection
3.7
External Antenna Feed Design
UM4B0 feeds the antenna signals to the required circuits internally, but in order to
effectively prevent damage from lightning and surges, circuit protection should be
installed externally to protect the module.
High voltage and high-power protection chips should be used to feed the antenna
from the outside of the module. A gas discharge tube, varistor, TVS tube and other
high-power protective devices may also be used in the antenna circuit to effectively
improve the prevention against lightning stroke and surge.
