Telit Wireless Solutions SL869T3-I, Руководство пользователя

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SL869T3-I Product User Guide
1VV0301546 Rev. 3
Page 44 of 68 2021-03-31
10. REFERENCE DESIGNS
10.1. SL869T3-I Reference Design
Figure 10-1 SL869T3-I Reference Design
Note/Tip: Pin 7 is RESERVED (no connection) on part numbers
SL869T3I001R001, SL869T3I001T001, SL869T3I001R002 and
SL869T3I001T002.
Along with power and ground, the minimum signals required to operate the module
properly are described below.
The power supply must have tight voltage regulation under varying line and load
conditions to prevent falsely tripping the internal voltage supervisor within the module.
The RF input is connected to a GNSS antenna that receives both L1 and L5 bands. The
reference design shows a DC power feed for an active antenna. The inductor L1 is chosen
to be self-resonant at the GPS frequency, 1.57542 GHz, to minimize loading on the RF
trace. Capacitor C5 is also chosen to be self-resonant at the GPS frequency such that it
is close to an RF short at that frequency. V_ANT is the supply voltage for the external
active antenna.
Since the SL869T3-I has no pre-select filter, if used in conjunction with a co-located
cellular module, an external L1-L5 double hump SAW filter is required to reduce the out
of band energy that would otherwise be applied to the input of the module.
TX and RX are typical UART digital I/O lines.