LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
System description
Page 24 of 125
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.
Three pins are allocated for
VCC
supply. Another twenty pins are designated for
GND
connection. Even if all the
VCC
pins and all the
GND
pins are internally connected within the module, it is recommended to properly
connect all of them to supply the module in order to minimize series resistance losses.
To avoid undershoot and overshoot on voltage drops at the start and end of a transmit burst during a GSM call
(when current consumption on the VCC supply can rise up to 2.5 A in the worst case), place a 330 µF low ESR
capacitor (e.g. KEMET T520D337M006ATE045) near the
VCC
pins.
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, place the following near the
VCC
pins:
100 nF capacitor (e.g Murata GRM155R61A104K) to filter digital logic noise from clocks and data sources
10 nF capacitor (e.g. Murata GRM155R71C103K) to filter digital logic noise from clocks and data sources
10 pF capacitor (e.g. Murata GRM1555C1E100J) to filter EMI in the 1800 / 1900 / 2100 MHz bands
39 pF capacitor (e.g. Murata GRM1555C1E390J) to filter EMI in the 850 / 900 MHz bands
Figure 9 shows the complete configuration but the mounting of each single component depends on the
application design.
3V8
C1
C4
GND
C3
C2
C5
LISA-U1 series
62
VCC
63
VCC
61
VCC
+
Figure 9: Suggested schematic design to reduce voltage ripple and noise and to avoid undershoot/ overshoot on voltage drops
Reference
Description
Part Number - Manufacturer
C1
330 µF Capacitor Tantalum D_SIZE 6.3 V 45 m
Ω
T520D337M006ATE045 - KEMET
C2
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
C3
10 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C103KA01 - Murata
C4
39 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1E390JA01 - Murata
C5
10 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1E100JA01 - Murata
Table 7: Suggested components to reduce voltage ripple and noise and to avoid undershoot/ overshoot on voltage drops
