Microchip Technology RN4870-I/RM128, Manual, Page: 20 / 55

2016-2021 Microchip Technology Inc. DS50002489E-page 17
RN4870/71
4.2 RN4870U Module
Figure 4-4 shows the physical dimensions of the
RN4870U module. Figure 4-5 illustrates the
recommended PCB layout and Figure 4-6 shows the
recommended mounting details.
A low-impedance ground plane ensures the best radio
performance (best range, lowest noise). Pin 30 (BT_RF)
is a 50 Ohm connection that can be connected to an
external antenna, such as a PCB trace antenna, a com-
ponent (chip) antenna or through a host PCB 50 Ohm
microstrip trace. This trace can be extended to include
passive parts for antenna attenuation padding,
impedance matching or to provide test posts. It is recom-
mended that the microstrip trace be as short as possible
for minimum loss and best impedance matching. If the
microstrip trace is longer, a 50 Ohm impedance is
recommended.
FIGURE 4-4: RN4870U MODULE DIMENSIONS