ZED-F9R-Integration manual
Figure 49: VCC pads
4.9 Design guidance
4.9.1 General considerations
Check power supply requirements and schematic:
• Is the power supply voltage within the specified range and noise-free?
• If USB is not used, connect the V_USB pin to ground.
• It is recommended to have a separate LDO for V_USB that is enabled by the module VCC. This is
to comply with the USB self-powered specification.
• If USB is used, is there a 1 uF capacitor right near the V_USB pin? This is just for the V_USB pin.
• Is there a 1 uF cap right next to the module VCC pin?
• Compare the peak current consumption of the ZED-F9R GNSS module with the specification of
your power supply.
• GNSS receivers require a stable power supply. Avoid series resistance (less than 0.2 Ω) in
your power supply line (the line to VCC) to minimize the voltage ripple on VCC. See the ZED-
F9R Power supply section in the Design chapter for more information on the power supply
requirements.
• Allow all I/O to Float/High impedance (High-Z) when VCC is not applied.
4.9.2 Backup battery
Check backup supply requirements and schematic:
• For achieving a minimal time to first fix (TTFF) after a power down (warm starts, hot starts),
make sure to connect a backup battery to V_BCKP.
• Verify that your battery backup supply can provide the battery backup current specified in the
applicable data sheet.
• Allow all I/O including UART and other interfaces to Float/High impedance in HW backup mode
(battery backup connected with VCC removed).
4.9.3 RF front-end circuit options
It is important that the RF input is fed by an active antenna meeting the requirements for
the ZED-F9R.
The first stages of the signal processing chain are crucial to the overall receiver performance.
When an RF input connector is employed this can provide a conduction path for harmful or
destructive electrical signals. If this is a likely factor the RF input should be protected accordingly.
UBX-20039643 - R06
4 Design Page 102 of 119
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