SL871 Family Product User Guide
1VV0301170 Rev. 9
Page 62 of 89
2021-07-15
Not Subject to NDA
11.
REFERENCE DESIGN
Figure 18: SL871 Family Reference Design
Along with power and grounds, the minimum signals required to operate the receiver
properly are the RF input signal and two digital signals (TX and RX). The RF input can be
connected directly to a passive GNSS antenna. The reference design shows a DC power
feed for an active antenna.
Warning: C1 is used to block the DC voltage from entering the
module, but is not required on SL871L modules since they include an
internal DC blocking capacitor.
Inductor L1 is chosen to be self-resonant at the GNSS frequency (approximately 1.57542
GHz) to minimize loading on the RF trace. Capacitor C2 is also chosen to be self-resonant
so that it is close to an RF short at the GNSS frequency.
Warning: Note that the ANT-ON signal is not available on the SL871
Gen 1, so the reference design must be modified accordingly.
The circuit shown does not provide input to ANT-OC and ANT-SC-N (SL871 only).
TX and RX are UART lines with a default of 9600-8-N-1. They are used for message output
and command input. Be careful not to drive the RX line if the module is turned off.
