ZED-F9P-Integration Manual
UBX-18010802 - R02
5 Hardware description Page 70 of 114
Advance Information
Use a LDO for the ZED-F9P that has an in built current limiter. This ensures that the charging
of module capacitance during power on does not draw too high a peak current. For example
a LDO with a current limiter of 500 mA. The ZED-F9P will require a minimum of 300 mA with
no voltage drop during normal powered operation.
Do not use any resistors or coils in the power line.
Do not add any series resistance greater than 0.2
Ω
to the VCC supply as it will generate input
voltage noise due to dynamic current conditions.
For the ZED-F9P module the equipment must be supplied by an external limited power source
in compliance with the clause 2.5 of the standard IEC 60950-1.
5.2.2 V_BCKP: Backup supply voltage
If the module supply has a power failure, the V_BCKP pin supplies the real-time clock (RTC) and
battery backed RAM (BBR). Use of valid time and the GNSS orbit data at start up will improve the
GNSS performance, as with hot starts and warm starts. If no backup battery is connected, the
module performs a cold start at power up.
Avoid high resistance on the V_BCKP line: During the switch from main supply to backup
supply, a short current adjustment peak can cause a high voltage drop on the pin with possible
malfunctions.
If no backup supply voltage is available, connect the V_BCKP pin to VCC.
Allow all I/O including UART and other interfaces to Float/High impedance in HW backup
mode (Battery Back-up connected with VCC removed). Please see the "interfaces" section.
Real-Time Clock (RTC)
The Real-Time Clock (RTC) is driven by a 32 kHz oscillator using an RTC crystal. If the main supply
voltage fails, and a battery is connected to V_BCKP, parts of the receiver switch off, but the RTC still
runs providing a timing reference for the receiver. This operating mode is called Hardware Backup
Mode, which enables all relevant data to be saved in the backup RAM to allow a hot or warm start
later.
5.2.3 ZED-F9P Power supply
The ZED-F9P high precision receiver requires a low noise, low dropout voltage, very low source
impedance power supply of 3.3V typically. No inductors or Ferrite beads should be used from LDO
to the module VCC pin. The peak currents need to be taken into account for the source supplying
the LDO for the module.
A power supply fed by 5V is shown in the figure below. This supply is intended just for the module.
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