User's Manual

SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R18 Advance Information Design-in
Page 100 of 206
C5 C8
GND
C7C6 C9
SARA-G3 / SARA-
U2
52
VCC
53
VCC
51
VCC
+
USB
Supply
C3
R4
θ
U1
I USB
IAC
I END
T PRG
SD
V
IN
V INSNS
MODE
ISEL
C2C1
5V
TH
GND
V
OUT
V OSNS
V REF
R1
R2
R3
Li-Ion/Li-Pol
Battery Pack
D1
B1
C4
Li-Ion/Li-Polymer
Battery Charger IC
D2
Ferrite Bead
or 0Ω
Figure 47: Li-Ion (or Li-Polymer) battery charging application circuit
Reference Description Part Number - Manufacturer
B1
Li-Ion (or Li-Polymer) battery pack with 470 : NTC
Various manufacturer
C1, C4
1 μF Capacitor Ceramic X7R 0603 10% 16 V
GRM188R71C105KA12 - Murata
C2, C6
10 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C103KA01 - Murata
C3
1 nF Capacitor Ceramic X7R 0402 10% 50 V
GRM155R71H102KA01 - Murata
C5
330 μF Capacitor Tantalum D_SIZE 6.3 V 45 m:
T520D337M006ATE045 - KEMET
C7
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
C8
56 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1E560JA01 - Murata
C9
15 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1E150JA01 - Murata
D1, D2
Low Capacitance ESD Protection
CG0402MLE-18G - Bourns
R1, R2
24 k: Resistor 0402 5% 0.1 W
RC0402JR-0724KL - Yageo Phycomp
R3
3.3 k: Resistor 0402 5% 0.1 W
RC0402JR-073K3L - Yageo Phycomp
R4
1.0 k: Resistor 0402 5% 0.1 W
RC0402JR-071K0L - Yageo Phycomp
U1
Single Cell Li-Ion (or Li-Polymer) Battery Charger IC
for USB port and AC Adapter
L6924U - STMicroelectronics
Table 29: Suggested components for Li-Ion (or Li-Polymer) battery charging application circuit
2.2.1.9 Guidelines for external battery charging and power path management circuit
Application devices where both a permanent primary supply / charging source (e.g. ~12 V) and a rechargeable
back-up battery (e.g. 3.7 V Li-Pol) are available at the same time as possible supply source should implement a
suitable charger / regulator with integrated power path management function to supply the module and the
whole device while simultaneously and independently charging the battery.
Figure 48 reports a simplified block diagram circuit showing the working principle of a charger / regulator with
integrated power path management function. This component allows the system to be powered by a permanent
primary supply source (e.g. ~12 V) using the integrated regulator which simultaneously and independently
recharges the battery (e.g. 3.7 V Li-Pol) that represents the back-up supply source of the system: the power path
management feature permits the battery to supplement the system current requirements when the primary
supply source is not available or cannot deliver the peak system currents.
A power management IC should meet the following prerequisites to comply with the module VCC requirements
summarized in Table 6:
x High efficiency internal step down converter, compliant with the performances specified in section 2.2.1.2
x Low internal resistance in the active path Vout – Vbat, typically lower than 50 m:
x High efficiency switch mode charger with separate power path control