SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11
Design-in
Page 72 of 157
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It is highly recommended to avoid an abrupt removal of the
VCC
supply during SARA-R4/N4 series
normal operations: the
VCC
supply can be removed only after
V_INT
goes low, indicating that the
module has entered Deep-Sleep Power Saving Mode or Power-Off Mode.
☞
See the section
, and in particular
, for the parts recommended to be
provided if the application device integrates an internal antenna.
2.2.1.10
Additional guidelines for VCC supply circuit design
To reduce voltage drops, use a low impedance power source. The series resistance of the supply lines
(connected to the modules’
VCC
and
GND
pins) on the application board and battery pack should also be
considered and minimized: cabling and routing must be as short as possible to minimize losses.
Three pins are allocated to
VCC
supply connection. Several pins are designated for
GND
connection. It is
recommended to correctly connect all of them to supply the module minimizing series resistance.
To reduce voltage ripple and noise, improving RF performance especially if the application device integrates
an internal antenna, place the following bypass capacitors near the
VCC
pins:
68 pF capacitor with Self-Resonant Frequency in the 800/900 MHz range (e.g. Murata
GRM1555C1H680J), to filter EMI in the low cellular frequency bands
15 pF capacitor with Self-Resonant Frequency in the 1800/1900 MHz range (as Murata
GRM1555C1H150J), to filter EMI in the high cellular frequency bands
10 nF capacitor (e.g. Murata GRM155R71C103K), to filter digital logic noise from clocks and data
100 nF capacitor (e.g. Murata GRM155R61C104K), to filter digital logic noise from clocks and data
An additional capacitor is recommended to avoid undershoot and overshoot at the start and at the end of
RF transmission:
100
µ
F low ESR capacitor (e.g Kemet T520B107M006ATE015), for SARA-R412M supporting 2G
10
µ
F capacitor (or greater), for the other SARA-R4/N4 series modules that do not support 2G
An additional series ferrite bead is recommended for additional RF noise filtering, in particular if the
application device integrates an internal antenna:
Ferrite bead specifically designed for EMI suppression in GHz band (e.g. Murata BLM18EG221SN1),
placed as close as possible to the
VCC
pins of the module, implementing the circuit described in
, to filter out EMI in all the cellular bands
