LISA-U2 series - System Integration Manual
UBX-13001118 - R19
Early Production Information
System description
Page 25 of 175
Additional recommendations for the VCC supply application circuits
To reduce voltage drops, use a low impedance power source. The resistance of the power supply lines
(connected to the
VCC
and
GND
pins of the module) on the application board and battery pack should also be
considered and minimized: cabling and routing must be as short as possible in order to minimize power losses.
It is recommended to properly connect all three
VCC
pins and all twenty
GND
pins of the module to the supply
source to minimize series resistance losses.
To avoid voltage drop undershoot and overshoot at the start and end of a transmit burst during a GSM call
(when current consumption on the
VCC
supply can rise up to as much as 2.5 A in the worst case), place a bypass
capacitor with large capacitance (more than 100 µF) and low ESR near the
VCC
pins, for example:
330 µF capacitance, 45 m
Ω
ESR (e.g. KEMET T520D337M006ATE045, Tantalum Capacitor)
The use of very large capacitors (i.e. greater then 1000 µF) on the
VCC
line and the use of the soft start function
provided by some voltage regulators must be carefully evaluated, since the voltage at the
VCC
pins must ramp
from 2.5 V to 3.2 V within 1 ms to allow a proper switch on of the module.
To reduce voltage ripple and noise, which should improve RF performance if the application device integrates an
internal antenna, place the following series ferrite bead and bypass capacitors near the
VCC
pins of the module:
Ferrite bead for GHz band noise (e.g. Murata BLM18EG221SN1) as close as possible to the
VCC
pins of the
module, implementing the circuit described in Figure 9, to filter EMI in all the GSM / UMTS bands.
68 pF capacitor with Self-Resonant Frequency in the 800/900 MHz range (e.g. Murata GRM1555C1H680J)
at the
VCC
line where it narrows close to the module (see Figure 9), to filter EMI in lower bands
15 pF capacitor with Self-Resonant Frequency in 1800/1900 MHz range (e.g. Murata GRM1555C1H150J)
at the
VCC
line where it narrows close to the module (see Figure 9), to filter EMI in higher bands
10 nF capacitor (e.g. Murata GRM155R71C103K) to filter digital logic noise from clocks and data sources
100 nF capacitor (e.g. Murata GRM155R61A104K) to filter digital logic noise from clocks and data sources
Figure 9 shows the complete configuration, but keep in mind that the mounting of each single
component depends on the application design. It is highly recommended to provide the series ferrite bead
and all the
VCC
bypass capacitors as described in Figure 9 and Table 10 if the application device integrates
an internal antenna.
C1
GND
C2
C4
LISA-U2 series
62
VCC
63
VCC
61
VCC
3V8
C5
+
LISA-U
series
C5
GND plane
VCC line
Capacitor with
SRF ~900 MHz
FB1
C1
C3 C4
FB1
Ferrite Bead
for GHz noise
C2
C3
Capacitor with
SRF ~1900 MHz
Figure 9: Suggested schematic and layout design for the VCC line; 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
330 µF Capacitor Tantalum D_SIZE 6.3 V 45 m
T520D337M006ATE045 - KEMET
FB1
Chip Ferrite Bead EMI Filter for GHz Band Noise
220
at 100 MHz, 260
at 1 GHz, 2000 mA
BLM18EG221SN1 - Murata
Table 10: Suggested components for VCC circuit close to module’ pins; highly recommended when using an integrated antenna
