GNSS Module Series
L76&L76-L_Hardware_Design 21 / 59
3 Power Management
These modules provide a power optimized architecture with built-in autonomous energy saving
capabilities to minimize power consumption at any given time. The receiver can be used in six operating
modes: Periodic mode, AlwaysLocate™ mode, GLP mode, Standby mode, and Backup mode for best
power consumption and Continuous mode used for best performance.
3.1. Power Unit
VCC is the supply voltage pin of the modules. It supplies power for the PMU which in turn supplies the
entire system and RTC domains. The load current of the VCC pin varies according to VCC voltage level,
processor load, and satellite acquisition. It is important to supply sufficient current and make sure the
power supply is clean and stable.
The V_BCKP pin supplies power for the RTC domain. If the VCC voltage drops under the acceptable
level, the V_BCKP pin keeps the RTC domain powered. To achieve quick startup and improve TTFF, the
RTC domain power supply should be valid during the interval when the VCC pin does not have a valid
level. SRAM memory also belongs to the RTC domain. If the VCC is not valid, the V_BCKP pin supplies
power for SRAM memory that contains all the necessary GNSS data and some of the user configuration
variables.
VDD_RF is an output pin, equal in voltage to the VCC input. In Continuous mode, VDD_RF pin supplies
power for the external active antenna or the LNA. In Standby mode, VDD_RF pin is turned off.
The two diodes in the following figure construct an OR gate to supply power for RTC domain. WAKEUP
pin belongs to RTC domain. The signal shown as red line in Figure 3 can open and close the switch. The
following steps will close or open the switch:
Step 1: The switch will be closed by default when VCC pin is supplying power (VCC off on).
Step 2: Keeping WAKEUP open or low and sending PMTK command can open the switch
(Continuous Backup).
Step 3: Keeping WAKEUP logic high can close the switch (Backup Continuous).
The modules’ internal power supply is shown below:
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