SARA-G3 series - System Integration Manual
UBX-13000995 - R06
Objective Specification
Design-in
Page 138 of 218
As an alternative to using an external voltage regulator, the
V_INT
supply output of SARA-G350 wireless
modules can be used to supply a u-blox 1.8 V GNSS receiver of the u-blox 6 family (or later u-blox
family). The
V_INT
supply is able to withstand the maximum current consumption of these positioning
receivers.
The
V_INT
supply output provides low voltage ripple (up to 15 mVpp) when the module is in active-
mode or in connected-mode, but it provides higher voltage ripple (up to 90 mVpp) when the module is
in the low power idle-mode with power saving configuration enabled by AT+UPSV (refer to
u-blox AT
Commands Manual [2]).
According to the voltage ripple characteristic of the
V_INT
supply output:
The power saving configuration cannot be enabled to properly supply by
V_INT
output any 1.8 V
GNSS receiver of the u-blox 6 family and any 1.8 V GNSS receiver of the u-blox 7 family with
TCXO
The power saving configuration can be enabled to properly supply by
V_INT
output any 1.8 V GNSS
receiver of the u-blox 7 family without TCXO
Additional filtering may be needed to properly supply an external LNA, depending on the characteristics
of the used LNA, adding a series ferrite bead and a bypass capacitor (e.g. the Murata
BLM15HD182SN1 ferrite bead and the Murata GRM1555C1H220J 22 pF capacitor) at the input of the
external LNA supply line.
Refer to the
GNSS Implementation Application Note [21] for additional guidelines using the
V_INT
supply
output of SARA-G350 wireless modules to supply a u-blox 1.8 V GNSS receiver.
illustrates the application circuit for SARA-G350 connection to a u-blox 3.0 V GNSS
receiver:
SDA
and
SCL
pins of SARA-G350 are directly connected to the related pins of the u-blox 3.0 V
GNSS receiver, with appropriate pull-up resistors: an I2C-bus Voltage Translator is not needed
because SARA-G350 DDC (I
2
C) pins are capable up to 3.3 V.
GPIO3
and
GPIO4
pins of SARA-G350 are connected to the u-blox 3.0 V GNSS receiver by means
of a general purpose Voltage Translator, needed for SARA-G350 generic digital pins because only 1.8
V capable.
GPIO2
is connected to the active-high enable pin of the external voltage regulator that supplies the
u-blox 3.0 V GNSS receiver to enable or disable the 3.0 V GNSS supply.
The
V_BCKP
supply output of SARA-G350 is directly connected to the
V_BCKP
backup supply input
pin of the u-blox 3.0 V GNSS receiver as in the application circuit for a u-blox 1.8 V GNSS
receiver.
