User's Manual

SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R18 Advance Information Design-in
Page 99 of 206
Reference Description Part Number - Manufacturer
C1
330 μF Capacitor Tantalum D_SIZE 6.3 V 45 m:
T520D337M006ATE045 - KEMET
C2
10 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C103KA01 - Murata
C3
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - 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
C6
1 nF Capacitor Ceramic X7R 0402 10% 50 V
GRM155R71H102KA01 - Murata
C6
10 μF Capacitor Ceramic X5R 0603 20% 6.3 V
GRM188R60J106ME47 - Murata
C7
22 μF Capacitor Ceramic X5R 1210 10% 25 V
GRM32ER61E226KE15 - Murata
C8
10 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1E100JA01 - Murata
D1
Schottky Diode 40 V 1 A
SS14 - Vishay General Semiconductor
L1
10 μH Inductor 20% 1 A 276 m:
SRN3015-100M - Bourns Inc.
R1
1 M: Resistor 0402 5% 0.063 W
RC0402FR-071ML - Yageo Phycomp
R2
412 k: Resistor 0402 5% 0.063 W
RC0402FR-07412KL - Yageo Phycomp
U1
Step-up Regulator 350 mA
AP3015 - Diodes Incorporated
Table 28: Example of components for VCC circuit with separate supply for SARA-G3 modules product version “02” onwards
2.2.1.8 Guidelines for external battery charging circuit
Application devices that are powered by a Li-Ion (or Li-Polymer) battery pack should implement a suitable battery
charger design as SARA-G3 and SARA-U2 series modules do not have an on-board charging circuit.
In the application circuit example described in Figure 47, a rechargeable Li-Ion (or Li-Polymer) battery pack, that
features proper pulse and DC discharge current capabilities and proper DC series resistance, is directly connected
to the VCC supply input of the module. Battery charging is fully managed by the STMicroelectronics L6924U
Battery Charger IC that, from a USB source (5.0 V typ.), charges as a linear charger the battery, in three phases:
x 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
x 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)
x 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.
The L6924U, as linear charger, is more suitable for applications where the charging source has a relatively low
nominal voltage (~5 V), so that a switching charger is suggested for applications where the charging source has
a relatively high nominal voltage (e.g. ~12 V, refer to the following section 2.2.1.9 for specific design-in), even if
the L6924U can also charge from an AC wall adapter as its input voltage range is tolerant up to 12 V: when a
current-limited adapter is used, it can operate in quasi-pulse mode, reducing power dissipation.