ZED-F9P - Integration Manual
UBX-18010802 - R01
5 Design
Page 44 of 64
Objective Specification - Confidential
During assembly of end-user devices which contain passive patch antennas, an ESD
discharge may occur during production when pre-charged antennas are soldered to the GNSS
receiver board. In such cases, use of external protection in front of LNA_IN is mandatory to
avoid device destruction.
ESD discharge cannot be avoided during assembly and / or field use. Note also that SAW filters are
susceptible to ESD damage.
ESD discharge into the RF input cannot always be avoided during assembly or field use
with this Circuit. To provide additional robustness an ESD protection diode, can be placed at
LNA_IN to GND.
5.3 ZED-F9P minimal design
The minimal electrical circuit for ZED-F9P operation using the UART1 interface is shown below
Figure 43: Minimal ZED-F9P design
The UART1 interface that is connected to the Host will usually also have the RTCM3 messages
required for RTK operation transferred on it. The optional UART2 interface can only be used for
RTCM3 messages and has no Host interface capabilities. This interface is primarily intended for
connection to a satellite correction receiver.
5.4 ZED-F9P antenna bias
Active antennas have an integrated low-noise amplifier. Active antennas require a power supply
that will contribute to the total GNSS system power consumption budget with additional 5 to 20
mA typically. If the customers do not want to make use of the Antenna Supervisor function and
the supply voltage of the ZED-F9P module matches the supply voltage of the antenna (e.g. 3.0 V),
they can use the filtered supply voltage VCC_RF output to supply the antenna. However a 10 Ohm
current limiting resistor is required to prevent against short circuits destroying the BIAS-T inductor.
