SARA-G3 series - System Integration Manual
UBX-13000995 - R06
Objective Specification
Design-in
Page 99 of 218
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 GRM155R71C104KA01 - Murata
C3
10 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C103KA01 - Murata
C4
56 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1E560JA01 - Murata
C5
15 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1E150JA01 - Murata
Table 16: Suggested components to reduce ripple / noise on VCC and to avoid undershoot/ overshoot on VCC voltage drops
ESD sensitivity rating of the
VCC
supply pins is 1 kV (Human Body Model 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
VCC
pins. Higher protection level
can be achieved by mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array)
close to accessible point.
2.1.1.7
Guidelines for external battery charging circuit
SARA-G3 modules do not have an on-board charging circuit.
a battery charger design, suitable for applications that are battery powered with a Li-Ion (or Li-Polymer)
cell.
In the application circuit, a rechargeable Li-Ion (or Li-Polymer) battery cell, that features proper pulse
and DC discharge current capabilities and proper DC series resistance, is directly connected to the
VCC
supply input of SARA-G3 module. Battery charging is completely managed by the STMicroelectronics
L6924U Battery Charger IC that, from a USB power source (5.0 V typ.), charges as a linear charger
the battery, in three phases:
Pre-charge constant current
(active when the battery is deeply discharged): the battery is charged
with a low current, set to 10% of the fast-charge current
Fast-charge constant current
: the battery is charged with the maximum current, configured by the value
of an external resistor to a value suitable for USB power source (~500 mA)
Constant voltage
: when the battery voltage reaches the regulated output voltage (4.2 V), the L6924U
starts to reduce the current until the charge termination is done. The charging process ends when the
charging current reaches the value configured by an external resistor to ~15 mA or when the charging
timer reaches the value configured by an external capacitor to ~9800 s
Using a battery pack with an internal NTC resistor, the L6924U can monitor the battery temperature to
protect the battery from operating under unsafe thermal conditions.
Alternatively the L6924U, providing input voltage range up to 12 V, can charge from an AC wall adapter.
When a current-limited adapter is used, it can operate in quasi-pulse mode, reducing power dissipation.