User's Manual

TOBY-R2 series - System Integration Manual
UBX-16010572 - R04 Design-in
Page 73 of 147
2.2.1.6 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.
In case of modules supporting 2G radio access technology, 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 as specified in the TOBY-R2 series Data Sheet [1]), place a bypass capacitor with large capacitance (at least
100 µF) and low ESR near the VCC pins, for example:
 330 µF capacitance, 45 m ESR (e.g. KEMET T520D337M006ATE045, Tantalum Capacitor)
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)
 15 pF capacitor with Self-Resonant Frequency in 1800/1900 MHz range (e.g. Murata GRM1555C1E150J)
 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
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
C3 C4
TOBY-R2 series
71
VCC
72
VCC
70
VCC
C1 C5
3V8
+
Recommended for
cellular modules
supporting 2G
Figure 32: Suggested schematic for the VCC bypass capacitors to reduce ripple / noise on supply voltage profile
Reference
Description
Part Number - Manufacturer
C1
15 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H150JA01 - Murata
C2
68 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H680JA01 - 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
Table 23: 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 32 / Table 23 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.