Product Specs
4
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Subject: Doc. No.: Rev: 0.6
UMC-STD31BPN Product Specification Page 45 of 55
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Form No.: 2-JT-00022-03_001
UMC-STD31BPN Product Specification
45
Preventing the coplanar grounding being quite close 50-OHM RF transmission lines shall be considered by
Developer when you do RF trace design connected to RF antenna pads of UMC-MT2731R on the
application board. It is better to have the keep-out gap which is 3 to 5 times of top layer RF trace width
between these RF lines and the grounding
Meanwhile, it is also important to reserve the pi-matching circuit design close to NAD antenna out pads as
possible
Avoid making RF layout trace of the primary antenna port cross the diversity antenna trace, and then this
would cause the poor antenna isolation to impact RF performance of the application board
8.9.1 Antenna detection
Following concept schematic diagram is a design example to build the antenna detection circuit by using
NAD AUXADC pin of AUXADC_VIN2 for monitoring NAD ANT_PTRX connection status with the external
passive antenna shunted with a grounded inductor. In this diagram
DC block: to play the role of isolating the detection signal with Antenna matching possibly consisted of the
grounded matching elements
RF block: to prevent RF signals being fed into the antenna detection circuitry
GPIO resistor: to limit the current draw when the external antenna is connected
Connected Case: NAD EINT pin would continuously send out the detection signal of the static high state; if
the external antenna is well-attached with the application board, the software reading value of
AUXADC_VIN2 is kept as static zero-Voltage
Disconnected Case: If any broken events happened on RF path between the external antenna and NAD
ANT_PTRX, AUXADC_VIN2 would read a high state voltage level generated by NAD EINT port