User's Manual

SARA-R4 series - System Integration Manual
UBX-16029218 - R03 Design-in
Page 35 of 94
2.2.1.4 Guidelines for VCC supply circuit design using a rechargeable Li-Ion or Li-Pol battery
Rechargeable Li-Ion or Li-Pol batteries connected to the VCC pins should meet the following prerequisites to
comply with the module VCC requirements summarized in Table 6:
 Maximum pulse and DC discharge current: the rechargeable Li-Ion battery with its related output circuit
connected to the VCC pins must be capable of delivering the maximum current occurring during a
transmission at maximum Tx power, as specified in SARA-R4 series Data Sheet [1]. The maximum discharge
current is not always reported in the data sheets of batteries, but the maximum DC discharge current is
typically almost equal to the battery capacity in Amp-hours divided by 1 hour.
 DC series resistance: the rechargeable Li-Ion battery with its output circuit must be capable of avoiding a
VCC voltage drop below the operating range summarized in Table 6 during transmit bursts.
2.2.1.5 Guidelines for VCC supply circuit design using a primary (disposable) battery
The characteristics of a primary (non-rechargeable) battery connected to VCC pins should meet the following
prerequisites to comply with the module VCC requirements summarized in Table 6:
 Maximum pulse and DC discharge current: the non-rechargeable battery with its related output circuit
connected to the VCC pins must be capable of delivering the maximum current consumption occurring
during a transmission at maximum Tx power, as specified in SARA-R4 series Data Sheet [1]. The maximum
discharge current is not always reported in the data sheets of batteries, but the max DC discharge current is
typically almost equal to the battery capacity in Amp-hours divided by 1 hour.
 DC series resistance: the non-rechargeable battery with its output circuit must be capable of avoiding a
VCC voltage drop below the operating range summarized in Table 6 during transmit bursts.
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.
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.