LEXI-R422 - System integration manual
UBX-23007449 - R02
Design-in
Page 45 of 108
C1-Public
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 µF low ESR capacitor (e.g Kemet T520B107M006ATE015)
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 (as 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
C1
GND
C2
C4
LEXI-R422
A13
VCC
A14
VCC
A12
VCC
3V8
C5
+
FB1
C3
C5
GND plane
VCC line
Capacitor with
SRF ~1900 MHz
C1
C3 C4
FB1
Ferrite bead
for GHz noise
C2
Capacitor with
SRF ~900 MHz
VCC
VCC
VCC
LEXI
Figure 26: Suggested design to reduce ripple / noise on VCC, highly recommended when using an integrated antenna
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
100 µF capacitor tantalum B_SIZE 20% 6.3V 15m
T520B107M006ATE015
–
Kemet
FB1
Chip ferrite bead EMI filter for GHz band noise
220
at 100 MHz, 260
at 1 GHz, 2000 mA
BLM18EG221SN1 - Murata
Table 18: 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 parts described in
