NEO-D9C - Integration manual
4.8 Design guidance
4.8.1 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 NEO-D9C module with the specification of your
power supply.
• 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 NEO-D9C
chapter for more information on the power supply requirements.
• All I/O (including UART) must not be pulled high before power ON.
• Any pull ups must be tied to module VCC to ensure they are at the correct state on power ON
and OFF.
• Allow all I/O to Float/High impedance (High-Z) when VCC is not applied.
4.8.2 RF front-end circuit options
It is mandatory that the RF input is fed by an active antenna meeting the requirements for
the NEO-D9C.
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.
Additional points on the RF input
• What is the expected quality of the signal source (antenna)?
• What is the external active antenna signal power?
• What is the bandwidth and filtering of the external active antenna?
• Do the combined L1/L2/L6 external antenna and filtering components meet the group delay
variation requirements? This is critical for RTK. Any implementation of a PCB mounted L1/L2/
L6 patch antenna and the required RF components should not be attempted without explicit
assistance of an antenna manufacturer who has experience in achieving the required group
delay variation and bandwidth performance for RTK. u-blox does not have a reference design or
recommended components list to achieve this.
Are destructive RF power levels expected to reach the RF input? Is interference from wireless
transmitters expected?
• What are the characteristics of these signals (duty cycle, frequency range, power range,
spectral purity)?
• What is the expected performance under interference conditions?
Is there a risk of RF input exposure to excessive ESD stress?
• In the field: Can the user access the antenna connector?
• PCB / system assembly: Is there risk that statically charged parts (e.g. patch antennas) may be
discharged through the RF input?
UBX-21031631 - R02
4 Design
Page 39 of 53
C1-Public
