SARA-R4 series - System Integration Manual
UBX-16029218 - R06
Design-in
Page 44 of 102
2.2.1.9
Additional guidelines for VCC supply circuit design
To reduce voltage drops, use a low impedance power source. The series resistance of the power 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 power losses.
Three pins are allocated to
VCC
supply. Several pins are designated for
GND
connection. It is recommended to
properly connect all of them to supply the module to minimize series resistance losses.
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 sources
100 nF capacitor (e.g. Murata GRM155R61C104K), to filter digital logic noise from clocks and data sources
10 µF capacitor (or greater), to avoid undershoot and overshoot at the start and end of RF Tx
A suitable series ferrite bead can be properly placed on the
VCC
line for additional noise filtering if required by
the specific application according to the whole application board design.
C2
GND
C5
SARA-R4 series
52
VCC
53
VCC
51
VCC
C1
3V8
C3
C4
Figure 17: Suggested schematic for the VCC bypass capacitors to reduce ripple / noise on supply voltage profile
Reference
Description
Part Number - Manufacturer
C1
68 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H680JA01 - Murata
C2
15 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H150JA01 - Murata
C3
10 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C103KA01 - Murata
C4
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C104KA01 - Murata
C5
10 µF Capacitor Ceramic X5R 0603 20% 6.3 V
GRM188R60J106ME47 - Murata
Table 14: Suggested components to reduce ripple / noise on VCC
The necessity of each part depends on the specific design, but it is recommended to provide all the bypass
capacitors described in Figure 17 / Table 14 if the application device integrates an internal antenna.
ESD sensitivity rating of the
VCC
supply pins is 1 kV (HBM according to JESD22-A114). Higher protection
level can be required if the line is externally accessible on the application board, e.g. if accessible battery
connector is directly connected to the supply pins. Higher protection level can be achieved by mounting
an ESD protection (e.g. EPCOS CA05P4S14THSG varistor) close to accessible point.
