SARA-G3 series - System Integration Manual
UBX-13000995 - R06 Objective Specification Design-in
Page 103 of 218
Combining a SARA-G3 wireless module with a u-blox GNSS positioning receiver, the positioning receiver
VCC supply is controlled by the wireless module by means of the “GNSS supply enable” function provided
by the GPIO2 of the wireless module. In this case the V_BCKP supply output of the SARA-G3 wireless
module can be connected to the V_BCKP backup supply input pin of the GNSS receiver to provide the
supply for the positioning real time clock and backup RAM when the VCC supply of the wireless module
is within its operating range and the VCC supply of the GNSS receiver is disabled. This enables the u-
blox GNSS receiver to recover from a power breakdown with either a hot start or a warm start
(depending on the duration of the positioning VCC outage) and to maintain the configuration settings
saved in the backup RAM. Refer to section 2.5.32.5.3 for more details regarding the application circuit
with a u-blox GNSS receiver.
On SARA-G300 and SARA-G310 modules, the V_BCKP supply output can be used to supply an external
32 kHz oscillator which provides a 32 kHz signal to the EXT32K input pin as reference clock for the RTC
timing, so that the modules can enter the low power idle-mode and can make available the RTC
functions.
The internal regulator for V_BCKP is optimized for low leakage current and very light loads. Do not
apply loads which might exceed the limit for maximum available current from V_BCKP supply, as
this can cause malfunctions in the module.
SARA-G3 series
Data Sheet
[1] describes the detailed
electrical characteristics.
V_BCKP supply output pin provides internal short circuit protection to limit start-up current and protect the
device in short circuit situations. No additional external short circuit protection is required.
ESD sensitivity rating of the V_BCKP supply pin is 1 kV (Human Body Model according to
JESD22-A114). Higher protection level can be required if the line is externally accessible on the
application board, e.g. if an accessible back-up battery connector is directly connected to V_BCKP
pin. Higher protection level can be achieved by mounting an ESD protection (e.g. EPCOS
CA05P4S14THSG varistor array) close to the accessible point.
2.1.2.2 Guidelines for V_BCKP layout design
RTC supply (V_BCKP) requires careful layout: avoid injecting noise on this voltage domain as it may
affect the stability of the 32 kHz oscillator.
To Next Page
Loading...
Need help?
General